Although bile juice has no digestive enzyme it is still considered to be very important during digestion of food. Why?

Is the chromosome number of the zygote, embryonic cells, and adult of a particular organism always constant? How is the constancy maintained in these three stages?

State Modern Periodic Law. What is some groups and periods in the Modern Periodic Table?

List four characteristics of the images formed by plane mirrors.

How is charcoal obtained from wood? Why is charcoal considered a better fuel than wood?

i. What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?

ii. What type of reaction is this?

iii. Write a balanced chemical equation to represent the above reaction.

OR

A brown substance ‘X’ on heating in air forms a substance ‘Y’. When hydrogen gas is passed over heated ‘Y’, it again changes back into ‘X’.

i. Name the substance ‘X’ and ‘Y’

ii. Name the type of chemical reactions occurring during both the changes.

iii. Write the chemical equations of the reactions.

Salt A commonly used in bakery products on heating gets converted into another salt B which itself is used for removal of hardness of water, and a gas C is evolved. The gas C when passed through lime water, turns it milky. Identify A, B, and C.

i. What is meant by periodicity in properties of elements with reference to the periodic table?

ii. Why do all the elements of the same group have similar properties?

iii. How will the tendency to gain electrons change as we move from left to right across a period? Why?

Leaves of a healthy potted plant were coated with Vaseline to block the stomata. Will this plant remain healthy for long? State three reasons for your answer.

OR

i. Why do fishes die when taken out of water?

ii. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

i. Write the functions of the following parts human male reproductive system:

a. Testis; b. Vas deferens; c. Urethra; d. Prostate

ii. List any two common pubertal changes that appear in humans males.

Explain how the sex of the child is determined at the time of conception in human beings.

Mention the total number of chromosomes along with sex chromosomes that are present in a human female and a human male. Explain how in sexually producing organisms the number of chromosomes in the progeny remains the same as that of the parents.

For which position of the object does a convex lens form a virtual and erect image? Explain with the help of a ray diagram.

(i) Define the term ‘volt’.

(ii) State the relation between work, charge and potential difference for an electric circuit. Calculate the potential difference between the two terminals of a battery if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to the other.

OR

(i) Define the term ‘coulomb’.

(ii) State the relationship between the electric current, the charge moving through a conductor and the time of flow.

Calculate the charge is passing through an electric bulb in 20 minutes if the value of current is 200 mA.

AB is a current-carrying conductor in the plane of the paper as shown in the figure. What are the directions of magnetic fields produced by it at points P and Q? Given r₁ > r₂, where will the strength of the magnetic field be larger?

(i) Distinguish between ionic and covalent compounds under the following properties:

(a) The strength of forces between constituent elements

(b) The solubility of compounds in water

(c) Electrical conduction in substances

(ii) Explain how the following metals are obtained from their compounds by the reduction process:

(a) Metal M which is in the middle of the reactivity series.

(b) Metal N which is high up in the reactivity series.

Given one example of each type.

OR

(i) Distinguish between ‘roasting’ and ‘calcination’. Which of these two is used for sulphide ores and why?

(ii) Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.

(iii) Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure copper.

A salt X is formed, and gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate.

Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write chemical equation of the reaction involved.

How are involuntary actions and reflex actions different from each other?

OR

(i) Why is the flow of signals in a synapse from the axonal end of one neuron to dendritic end of another neuron but not the reverse?

(ii) Sameer was studying in his room. Suddenly he smells something burning and sees smoke in the room. He rushes out of the room immediately. Was Sameer’s action voluntary or involuntary? Why?

(i) What is myopia? State the two causes of myopia. With the help of labelled ray diagrams show

(a) The eye defect myopia

(b) Correction of myopia using a lens.

(ii) Why is the normal eye unable to focus on an object placed within 10 cm from the eye?

Draw an appropriate schematic diagram showing common domestic circuits and discuss the importance of fuse. When is it that a burnt out fuse should be replaced by another fuse of identical rating?

Explain some harmful effects of agricultural practices on the environment.

Solid sodium bicarbonate was placed on a strip of pH paper. What was the change in colour?

You have four beakers A, B, C and D. Out of A and B one has hard water and the other has soft water. Out of C and D, one has soap solution, and the other has a detergent solution. How would you identify these liquids?

OR

A gas is liberated immediately with a brisk effervescence when you add acetic acid to sodium hydrogen carbonate powder in a test tube. Name the gas and describe the test that confirms the identity of the gas.

The following experimental set-ups were kept in the laboratory to show that ‘CO₂ is given out during respiration’.

After 2 hours, in which the delivery tube does the water rise?

Name the type of asexual reproduction in which two individuals are formed from a single parent and the parental identity is lost. Write the first step from where such a type of reproduction begins. Draw first two stages of this reproduction.

Identify

(i) PQ (ii) ∠LMR

(iii) NN2 (iv) RS

The current flowing through a resistor connected in an electrical circuit and the potential difference developed across its ends are shown in the given diagrams.

Find the value of resistance of the resistor in ohms.

What will happen to a plant if its xylem is removed?

Colonies of yeast fail to multiply in water, but multiple in sugar solution. Give one reason.

i) Which two criteria did Mendeleev use to classify the elements in his periodic table?

ii) State Mendeleev’s periodic law.

i) Explain why a ray of light passing through the centre of curvature of a concave mirror gets reflected along the same path.

ii) Draw the given diagram in your answer-book and complete it for the path of a ray of light beyond the lens.

What is the main constituent of biogas? How is biogas obtained from biomass? Write any two advantages of using this gas.

An apparatus was set-up as shown in the figure. It was observed that when an aqueous solution of HCl was taken in the beaker and the circuit was closed, the bulb in the circuit began to glow, but it did not glow when the experiment was repeated with glucose solution. What could be the reason?

Would the bulb glow if the same experiment is repeated with an aqueous solution of

i. NaOH

ii. NaCl? Why?

2 g of ferrous sulphate crystals were heated in a hard glass test tube and observations recorded.

i. What was the successive colour change?

ii. Identify the liquid droplets collected on the cooler parts of the test tube.

iii. What type of odour is observed on heating ferrous sulphate crystals?

iv. Name the products obtained on heating ferrous sulphate crystals.

v. What type of reaction is taking place?

i) Why could no fixed position be given to hydrogen in Mendeleev’s periodic table?

ii) How and why does the atomic size vary as you go:

a. from left to right along a period?

b. down a group?

OR

i) Why did Mendeleev have gaps in his periodic table?

ii) How does electronic configurations of atoms change in a period with an increase in atomic number?

Draw a diagram of the human alimentary canal and label on it:

Oesophagus, Gall bladder, Liver and Pancreas.

OR

Draw a diagram of the excretory system in human beings and label on it:

Aorta, vena cava, urinary bladder, urethra.

i) Explain the terms:

a. implantation

b. placenta

ii) What is the average duration of human pregnancy?

Explain analogous organs and homologous organs. Identify the analogous and homologous organs amongst the following:

Wings of an insect, wings of a bat, forelimbs of frog, forelimbs of a human.

Distinguish between inherited traits and acquired traits giving one example of each. Give a reason why traits acquired by an individual during life time are not inherited.

An object is placed perpendicular to the principal axis of a convex lens of focal length 8 cm. The distance of the object from the lens is 12cm. Find the position and nature of the image.

OR

Define the term magnification as referred to spherical mirrors. If a concave mirror forms a real image 40 cm from the mirror, when the object is placed at a distance of 20 cm from its pole, find the focal length of the mirror.

What is meant by overloading of an electrical circuit? Explain two possible causes due to which overloading may occur in a household circuit. Explain one precaution that should be taken to avoid the overloading of the domestic electric circuit.

Two resistors, with resistances 5Ω and 10Ω respectively are to be connected to a battery of emf 6V so as to obtain:

Minimum current flowing

Maximum current flowing

i) How will you connect the resistances in each case?

ii) Calculate the strength of the total current in the circuit in the two cases.

Account for the following:

i) Melting and boiling points of ionic compounds are high.

ii) Aluminium is more active than iron, yet there is less corrosion of aluminium when both are exposed to air.

iii) Solder is used for welding electrical wires together.

iv) A sulphide ore is converted into its oxide to extract the metal.

v) Tarnished copper vessels are cleaned with tamarind juice.

i) Write a chemical equation of each of the following types of chemical reactions of organic compounds.

a. Oxidation reaction

b. Addition reaction

c. Substitution reaction

ii) What is ethanol? What happens when it is heated with excess conc. H₂SO₄ at 443 K? Write the role of conc. H₂SO₄ in this reaction.

i) Name the plant growth hormone which is synthesized at the shoot tip. Explain briefly why does a plant shoot bend towards light during its growth.

ii) With the help of a schematic diagram, trace the sequence of events occurring, when you step on a sharp object. Name this action.

OR

i) Compare and contrast nervous and hormonal mechanism for control and coordination in animals.

ii) a. Draw a diagram of the human brain.

b. The label on it cerebrum, cerebellum.

c. What is the role of the cerebellum?

i) What is a magnetic field? How can the direction of magnetic field lines at a place be determined?

ii) State the rule for the direction of the magnetic field produced around a current carrying conductor. Sketch the pattern of field lines due to a current flowing through a straight conductor.

OR

i) What is a solenoid? Sketch the pattern of field lines of the magnetic field through and around a current carrying solenoid.

ii) Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

A person is unable to see distinctly the words printed on a newspaper. Name the defect of vision he is suffering from. Draw ray diagram to illustrate this defect. List its two possible causes. Draw a ray diagram to show how this defect may be corrected using a lens of appropriate focal length.

i) What is sustainable development? Why is it necessary?

ii) What is water harvesting? List its four benefits.

The pH values of four solutions A, B, C and D as determined by a student 3, 7, 12, and 8 respectively

i) Identify the most acidic and most basic solutions.

ii) Arrange the above four solutions in the decreasing order of their hydrogen ion concentration.

What do you observe when you add sodium to acetic acid? How would you identify the gas released in the reaction? Describe briefly.

While doing the experiment to show light is necessary for photosynthesis; the student was given following suggestions by his fellow students. Which are the correct suggestions given by his fellow students?

i) Safranin should be used instead of iodine.

ii) The leaf should be boiled in alcohol with water bath to remove chlorophyll.

iii) Transparent paper strip should be used instead of black paper strip.

iv) The plant should be destarched before starting the experiment.

Draw a diagram showing different parts of an embryo of gram seed and label them.

In the experiment ‘To trace the path of ray of light passing through a glass prism’.

i) What is the correct set-up?

ii) Justify for your correct set-up.

When a (60 W, 220V) bulb and a (100 W, 220 V) bulb are connected in series, then which bulb will glow brighter?

OR

In a voltmeter, there are 20 divisions between the 0 mark and 0.5 V mark. Calculate the least count of the voltmeter.

In a bisexual flower inspire of the young stamens being removed artificially, the flower produces fruit. How is it possible?

Which part of the root is involved in the exchange of respiratory gases in plants?

Elements have been arranged in the following sequence on the basis of their increasing atomic masses.

F, Na, Mg, Al, Si, P, S, Cl, Ar, K

i. Pick two sets of elements which have similar properties.

ii. The given sequence represents which law of classification of elements?

An object is placed at a distance of 30cm from a concave lens of focal length 15cm. List four characteristics (Nature, position. Etc.) of the image formed by the lens.

Describe how hydro-energy can be converted into electrical energy. Write any two limitations of hydro-energy.

Identify the oxidising agent (oxidant) in the following reactions.

i. pb₃O₄ + 8HCl → 3pbCl₂ + Cl₂ + 4H₂O

ii. 2Mg + O₂→ 2MgO

iii. CuSO₄ + Zn → Cu + ZnSO₄

iv. V₂O₅ + 5Ca → 2V + 5CaO

v. 3Fe + 4H₂O → Fe₃O₄ + 4H₂

vi. CuO + H₂→ Cu + H₂O

Crystals of copper sulphate are heated in a test tube for some time.

i. What is the colour of copper sulphate crystals

a. before heating, and b. after heating?

ii. which one of these has a higher concentration of H⁺ ions?1 M HCL or 1M CH₃COOH

An element X (atomic number 17) reacts with an element Y (atomic number 20) to form a divalent halide.

i. Where in the Periodic Table are elements X and Y placed?

ii. Classify X and Y as metal(s),non-metal(s) or metalloid (s).

iii. What will be the nature of oxide of element Y? Identify the nature of bonding in the compound formed.

iv. Draw the electron dot structure of the divalent halide.

The following table shows the position of six elements A, B, C, D, E and F in the Periodic Table.

Using the above the table answer the following questions:

i. Which element will from only covalent compounds?

ii. Which element is a metal with valency 3?

iii. Which element is a non-metal valency 3?

iv. Write a common name for the family of elements C and F.

v. Out of D and E, which one has a bigger atomic radius and why?

What are the adaptations of leaf for photosynthesis?

What is vegetative propagation? State two advantages and two disadvantages of this method

Distinguish between the acquired traits and the inherited traits in tabular form, giving one example for each.

OR

Explain with the help of example each, how the following provide evidences in favour of evolution:

i. Homologous organs

ii. Analogous organs

iii. Fossils

The genotype of green-stemmed tomato plants is denoted as GG and that of purple-stemmed tomato plants as gg. When these two are crossed,

I. What colour of stem would you expect in their F₁ progeny?

ii. Give the percentage of purple-stemmed plants if F₁ plants are self-pollinated.

In what ratio would you find the genotyped GG and Gg in the F₂ progeny?

An object 4 cm in height, is placed at 15 cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a sharp image of the object. Calculate the height of the image.

OR

At what distance form a concave lens of focal length 20cm a 6cm tall object be placed so as to obtain its image at 15cm from the lens? Also calculate the size of the image formed. Draw a ray diagram to justify your answer for the above situation and label it.

i. Calculate the resistance of an electric bulb which allows a 10A current when connected to a 220 V power source.

ii. Draw a schematic diagram of an resistance of an electric circuit consisting of a battery of two cells each of 1.5 V, 5 Ω, 10Ω and 15Ω resistors and a plug key, all connected in series.

i. Explain an activity to show that a current-carrying conductor experiences a force when placed in a magnetic field.

ii. State the rule which gives the direction of force acting on the conductor.

i. Giving one example of each, explain how the following metals are obtained from their compounds by the process of reduction.

a. Meta ‘A’ which is low in the activity series of metals.

b. Metal ‘B’ which is in the middle of the activity series of metals.

ii. What is meant by refining of metals? In the electrolytic refining of metal M, name the cathode, anode and the electrolyte.

An organic compound A having molecular formula C₂H₄O₂ reacts with sodium metal and evolves a gas B which readily catches fire. An also reacts with ethanol in the presentce of conc H₂SO₄ TO form sweet smelling substance C used in making perfumes.

i. Identify the compounds A, B, and C and write their names.

ii. Write balanced chemical equations of represent conversion of

a. compound A into compound B

b. compound A into compound C

iii. Write the chemical composition of detergents. Mention their advantage over soaps for washing clothes.

OR

i. What are hydrocarbons? Give one example. with two examples each.

ii. Give the structural differences between started and unsaturated hydrocarbons

iii. What is a functional group? Give examples of two different functional group.

How are involuntary actions and reflex actions different from each other?

With the help of an activity show the blue colour of the sky and the reddish appearance of the sun at the sunrise or sunset.

Explain the underlying principle and working of direct current generator (or DC dynamo) by drawing a labelled diagram.

i. State two advantages of conserving (a) forests, and (b) wildlife.

ii. Explain two main advantages associated with water harvesting at the community level.

iii. In the following food chain, 100 J of energy is available to the lion. How much energy was available to the producer?

Plants → Deer → Lion

OR

i. Write the full name of the group of compounds mainly responsible for the depletion of ozone layer.

ii. prepare a list of five activities that you perform daily in which natural resources can be conserved or energy utilisation can be minimised.

During an experiment, Amit observed that blue colour of aqueous copper sulphate solution changed to pale green by immersing a metallic rod for some time.

i. Which metallic rod Amit might have immersed in the solution and What colour would be observed on the rod?

ii. mention the type of reaction in this case.

A student adds a spoonful of powdered sodium hydrogen carbonate to a flask containing ethanoic acid. List two main observations, he must note in his notebook, about the reaction that takes place. Also, write chemical equation for the reaction.

A student sets up the apparatus for the experiment to show that CO₂ is released during respiration. After 2 hours, what would he observe?

Draw a labelled diagram to show that particular stage of binary fission in Amoeba in which its nucleus elongates and divide into two and a constriction appears in its cell membrane.

In the given figure, a narrow beam of white light is shown to pass through a triangular glass prism. After passing through the prism it produces a spectrum on a screen.

Which two positions correspond closely to the colour of

i. egg yolk,

ii. ladyfinger?

In an experiment to find the equivalent resistance of a series combination of two resistors R₁ and R₂, a student uses the circuit shown here. Will the circuit give the correct reading for current I and voltage V? Justify your answer.

OR

The given circuit diagram shows the experimental arrangement of different circuit components for determination of equivalent resistance of two resistors connected in series. Identify the components X, Y and Z shown in the circuit respectively.

Name the green dot-like structures in some cells observed by a student when a leaf peel was viewed under a microscope. What is this green colour due to?

In a germinating seed, which parts are known as future shoot and future root? Mention the function of cotyledon.

How many groups and periods are there in the Modern Periodic Table? How do the atomic size and metallic character of elements vary as we move:

i. down a group and

ii. from left to right in a period?

A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object place from the lens? Draw the ray diagram.

Mention any four limitations in harnessing wind energy on a large scale.

No chemical reaction takes place when granules of a solid, A are mixed with the powder of another solid, B. However when the mixture is heated, a reaction takes place between its components. One of the products, C is a metal and settles down in the molten state while the other product, D floats over it. It was observed that the reaction is highly exothermic.

i. Based on the given information make an assumption about A and B and write a chemical equation for the chemical reaction indicating the conditions of reaction, physical state of reactants and products and thermal status of reaction.

ii. Mention any two types of reactions under which above chemical reaction can be classified.

What happens when dilute hydrochloric acid is added to the following and write balanced chemical equations:

i. Bleaching powder

ii. Zinc granules

iii. Baking soda

OR

You have two solutions A and B. The pH of the solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of these is acidic and which one is basic?

Atoms of eight elements A, B, C, D, E, F, G and H have the same number of electronic shells but different number of electrons in their outermost shell. It was found that elements A and G combine to form an ionic compound. This compound is added in a small amount to almost all vegetable dishes during cooking. Oxides of elements A and B are basic in nature while those of E and F are acidic. The oxide of D is almost neutral. Based on the above information answer the following questions:

i. To which group or period of the periodic table do the listed elements belong?

ii. What would be the nature of compound formed by a combination of elements B and F?

iii. Which two of these elements could definitely be metals?

iv. Which one of the eight elements is most likely to be found in gaseous state at room temperature?

v. If the number of electrons in the outermost shell of elements C and G be 3 and 7 respectively, write the formula of the compound formed by the combination of C and G.

i. Explain why the rate of photosynthesis in plants is low both at lower and higher temperatures.

ii. Is green light most or least useful in photosynthesis and why?

OR

Why does absorption of digested food occur mainly in the small intestine?

What is vegetative propagation? State two advantages and two disadvantages of this method.

How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?

“Evolution and classification of organisms are interlinked.” Give reasons to justify this statement.

At what distance should an object be placed from a convex lens of focal length 18 cm to obtain an image at 24cm from it on the other side. What will be the magnification produce in this case?

Given that R₁ = 10 Ω, R₂ = 40Ω, R₃ = 30Ω, R₄ = 20Ω and R_A is the parallel combination of R₁ and R₂ whereas RB is the parallel combination of R₃ and R₄. Combination R_A is connected to the positive terminal of 12 V battery while combination R_B is connected to the negative terminal. Ammeter A is connected between the resistors R_A and R_B.

(i) Find R_A and R_B Also calculate total resistance in the circuit.

(ii) Daw the circuit diagram showing above combinations connected to battery and ammeter.

State the rule to determine the direction of a

(i) magnetic field produced around a straight conductor-carrying current

(ii) force experienced by a current carrying straight conductor placed in a magnetic field which is perpendicular to it and

(iii) current induced in a coil due to its rotation in a magnetic field.

OR

What is the role of fuse used in series with any electrical appliance? Why should a fuse with defined rating not be replaced by one with a larger rating?

Write the names and symbols of two most reactive metals belonging to group I of the periodic table. Explain by drawing electronic structure how either one of the two metals reacts with a halogen. With which name is the bond formed between these elements known and what is the class of the compound so formed known? State any four physical properties of such compounds.

Why certain compounds are called hydrocarbons? Write the general formula for homologous series of alkenes, alkenes and also draw the structure of the first member of each series. Write the name of the reaction that converts alkenes into alkenes and also write a chemical equation to show the necessary conditions for the reaction to occur.

i. (a) which part of the nervous system controls reflex arcs?

(b) With the help of a diagram trace the sequence of events, which occur when we touch a hot object.

(c) Mention the part of the neuron that acquires information and the form in which information travels.

ii. Name the hormone synthesised at the shoot tips. How does it help the plant to response to light?

OR

i. What causes tendril to encircle or coil around the object in contact with it? Explain the process involved.

ii. What is chemotropism? Give one example.

i. A student suffering from myopia is not able to see distinctly the objects paced beyond 5m. List two possible reasons due to which this defect of vision may have arisen. With the help of ray diagrams, explain

(a) Why the student is unable to see distinctly the objects placed beyond 5 m from his eyes.

(b) The type of the corrective lens used to restore proper vision and how this defect is corrected by the use of this lens.

ii. If, in this case, the numerical value of the focal length of the corrective lens is 5 m, find the power of the lens as per the new Cartesian sign convention.

i. Draw the pattern of magnetic field lines through and around a current-carrying solenoid. What does the magnetic field pattern inside the solenoid indicate?

ii. How can this principle be utilised to make an electromagnet?

iii. State two ways by which strength of this electromagnet can be increased.

OR

Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

i. (a) Water is an elixir of life, a very important natural resource. Your Science teacher wants you to prepare a plan for a formative assessment activity, “How to save water, the vital natural resource”. Write any two ways that you will suggest to bring awareness in your neighbourhood, on ‘how to save water.’

(b) Name and explain any one way by which the underground water table does not go down further.

ii. Explain two main advantages associated with water harvesting at the community level.

A student dips pH papers in solutions A and B and observes that the pH paper turns blue and orange respectively in them. What does he infer?

OR

A student took the following samples to find out their pH using pH paper: dilute hydrochloric acid, lemon juice, washing soda and soap solution. The teacher remarked that one of the samples taken was not proper. To which sample was the teacher referring to?

When asked to set up an experiment to show that ‘light is necessary for photosynthesis’ , a student ran to the school garden and set up the experiment using a plant growing in the school garden. The experiment failed. His fellow student made the following suggestions to get success.

Student A: Safranin should be used instead of iodine.

Student B: The leaf should not be boiled in alcohol to remove chlorophyll before testing for starch.

Student C: Transparent paper strip should be used instead of black paper strip.

Student D: The plant should be de- starched before starting the experiment.

Which student made the right suggestion?

What will happen if a student while studying the dependence of current on the potential difference keeps the circuit closed for a long time to measure the current and potential difference?

Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.

Draw in sequence (showing the four stages), the process of binary fission in Amoeba.

A beam of white light falling on a glass prism gets split up into seven colours marked 1 to 7 as shown in the diagram.

A student makes the following statements about the spectrum observed on the screen.

i. The colours at positions marked 3 and 5 are similar to the colour of the sky and the colour of gold metal respectively.

ii. Which two positions correspond closely to the colour of?

(a) brinjal,

(b) ‘Danger’ or stop signal lights?

Why does lack of oxygen in muscles often lead to cramps among cricketers?

Name the method by which Hydra reproduces. Is this method sexual or asexual?

Define the following terms:

i. Valency

ii. Atomic size

Draw a ray diagram to show the path of the reflected ray corresponding to an incident ray which is direct towards the principal focus of a convex mirror. Mark on it angle of incidence and the angle of reflection.

What is meant by biodiversity? List two advantages of conserving forest and wildlife.

During the reaction of some metals with dilute hydrochloric acid, following observations were made.

i. The temperature of the reaction mixture rises when aluminium (Al) is added.

ii. The reaction of sodium metal is found to be highly explosive.

iii. Some bubbles of a gas are seen when lead (Pb) is reacted with the acid.

Explain these observations giving suitable reasons.

In one of the industrial processes used for manufacture of sodium hydroxide, a gas X is formed as by-product. The gas X reacts with lime water to give a compound Y which is used as a bleaching agent in chemical industry. Identify X and Y giving the chemical equation of the reactions involved.

Na, Mg and Al are the elements of the 3rd period of the Modern periodic Table having group number 1,2 and 13 respectively. Which one of these elements has the (i) highest valency, (ii) largest atomic radius, and (iii) maximum chemical reactivity? Justify your answer stating the reason for each.

OR

Based on the group valency of elements, state the formula for the following giving justification for each:

i. Oxides of group 1 elements

ii. Halides of the elements of group 13 and

iii. Compounds formed when an element of group 2 combines with an element of group 16.

Study the given diagram:

Name the parts ‘A’ and ‘B’ and state one function of each.

OR

How are fats digested in our bodies? Where does this process take place?

i. Write the functions of the following parts of human male reproductive system:

(a) Testis

(b) Vas deferens

(c) Urethra

(d) Prostate

ii. List any two common pubertal changes that appear in human males.

How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?

“Evolution and classification or organisms are interlinked”. Give reasons to justify this statement.

If the image formed by a lens for all positions of an object placed in front of it is always erect an diminished, what is the nature of this lens? Draw a ray diagram to justify your answer.

If the numerical value of the power of this lens is 10 D, what is its focal length in the Cartesian system?

Three 2Ω resistors A, B and C are connected as shown in figure. Each of them dissipates energy and can with stand a maximum power of 18 W without melting. Find the maximum current that can flow through the three resistors.

OR

Draw a circuit diagram of an electric circuit containing a cell, a key, an ammeter, a resistor of 2Ω in series with a combination of two resistors (4Ωeach) in parallel and a voltmeter across the parallel combination. Will the potential difference across the 2Ωresistor be same as that across the parallel combination of 4Ω resistors? Give reason.

The given magnet is divided into three parts A, B and C.

Name the parts where the strength of the magnetic field is:

i. maximum

ii. minimum

How will density of magnetic field lines differs at these parts?

i. In the formation of compound between two atoms A and B, A loses two electrons and B grains one electron.

A. What is the nature of bond between A and B?

B. Suggest the formula of the compound formed between A and B.

ii. On similar lines explain the formation of MgCl2 molecule.

iii. Common salt conducts electricity only in the molten state. Why?

iv. Why is melting point of NaCl high?

Elements forming ionic compounds attain noble gas configuration by either gaining or losing electrons from their outermost shells. Give reason to explain why carbon cannot attain noble gas configuration in this manner to form its compounds. Name the type of bonds formed in ionic compounds and in the compounds formed by carbon. Also give reason why carbon compounds are generally poor conductors of electricity.

OR

i. State the meaning of functional group in a carbon compound. Write the functional group present in (a) ethanol and (b) ethanoic acid and also draw their structures.

ii. Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen can take place. Stating the essential conditions required for an additional reaction to occur write the chemical equation giving the name of the reactant and the product of such a reaction.

i. Name the part of brain which controls

A. voluntary action,

B. involuntary action.

ii. What is the significance of the peripheral nervous system? Name the components of this nervous system and distinguish between the origin of the two.

iii. A. Identify the glands that secrete

• Insulin

• Thyroxin

B. Explain with an example how the timing and amount of hormone secreted are regulated in human body.

i. List the parts of the human eye that control the amount of light entering into it. Explain how they perform this function.

ii. Write the function of retina in human eye.

iii. Do you know that the corneal-impairment can be cured by replacing the defective cornea with the cornea of the donated eye? How and why should we organise groups to motivate the community members to donate their eyes after death?

i. Define electromagnetic induction.

ii. Two coils P and S are wound over the same iron core. Coil P is connected to battery and key and the coil S is connected to galvanometer. Draw a suitable diagram of this arrangement and write your observations when:

A. Current in the coil P is started by closing the key.

B. Current continues to flow in coil P.

C. Current in coil P is stopped by removing the key.

Explain the reason for such observations.

OR

Briefly explain an activity to plot the magnetic field lines around a bar magnet. Sketch the field pattern for the same specifying field directions.

A region A has magnetic field lines relatively closer than another region B. Which region has stronger magnetic field. Give reason to support your answer.

i. What is ‘Chipko Movement’? Why should we conserve forests?

ii. Suggest any four changes that you would like to be incorporated in the life-style of students of your age to move towards a sustainable use of available resources.

iii. An environmentalist on visit to your school suggested the use of three R’s to save the environment. Explain what he meant by three R’s and how you would follow his advice at home.

While performing an experiment, a student observes that when he heats some green crystals in a boiling tube, the colour of the crystals changes to brown and a gas evolves which smells like burning sulphur. Interpret the observations and results.

A student is studying the properties of acetic acid in his school laboratory. List two physical and two chemical properties which he must observe and note in his record book.

Two physical and two chemical properties that must be observed and noted are:

The following experiment was set-up to show that a gas is given out during respiration. But there was no rise in the level of water. Why did it happen?

A student is observing a permanent slide showing sequentially the different stages of asexual reproduction taking place in yeast. Name this process and draw diagram of what he observes in a proper sequence.

In an experiment on tracing the path of a ray of light through a rectangular glass slab, four students A, B, C and D used the following values of angle of incidence and the distance between the feet of the two pins (fixed on the incident ray):

A. (30°, 45°, 60°) and 1 cm

B. (30°, 45°, 60°) and 6 cm

C. (20°, 50°, 80°) and 10 cm

D. (20°, 50°, 80°) and 15 cm

Whose choice is the best choice and why?

The rest positions of the needles in a milliammeter and voltmeter not in use are as shown in Fig. A. When a student uses these in his experiment, the readings of the needle are in the positions shown in Fig. B.

Find the corrected values of current and voltage in the experiment.

OR

While experimentally verifying Ohm’s law a student observed that the pointer of the voltmeter coincides with 15thdivision when the voltmeter has a least count of 0.05 V. Find the observed reading of voltmeter.

How many molecules of water of crystallisation are there in

i. Plaster of Paris

ii. washing soda crystals?

Write the molecular formula of first two members of homologous series having functional group – Cl.

Why is a normal eye not able to see clearly the objects placed closer than 25 cm?

List two biotic components of a biosphere.

Management of forest and wildlife resources is a very challenging task. Why? Give any two reasons.

i. Give an example for a combination reaction which is exothermic.

ii. Identify the oxidising agent, reducing agent in the following reaction:

H₂S + Cl₂⇒ 2HCl + S

iii. Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in open. Suggest one method to prevent it.

A reddish brown coloured metal, used in electrical wires, when powdered and heated strongly in an open china dish, its colour turns black. When hydrogen gas in passed over this black substance, it regains its original colour. Based on the above information answer the following questions.

i. Name the metal and the black coloured substance formed.

ii. Write balanced chemical equations for both the reactions.

Two carbon compounds X and Y have the molecular formula C₄H₈ and C₅H₁₂ respectively. Which one of these is most likely to show addition reaction? Justify your answer. Also, give the chemical equation to explain the process of addition reaction in this case.

OR

Complete the following chemical equations:

i. CH₃COOC₂H₅ + NaOH →

ii. CH₃COOH + NaOH →

iii. C₂H₅OH+CH₃COOH

Explain how the human body responds when adrenaline is secreted into the blood.

OR

How does chemical coordination take place in animals?

Mention the total number of chromosomes along with the sex chromosomes that are present in a human female and a human male. Explain how in sexually producing organisms the number of chromosomes in the progeny remains the same as that of the parents.

“Natural selection and speciation leads to evolution”. Justify this statement.

A child while playing with his father’s spectacles burnt a hole in a piece of paper by focusing a small image of the sun on it.

i. What defect of vision his father is suffering from?

ii. Write two causes for this defect.

iii. Draw a ray diagram to show image formation by the defective eye.

iv. Draw a ray diagram showing corrected eye using proper lens.

OR

A person cannot see objects beyond 80 cm from his eye while a person with normal eyesight can see object easily placed up to 160 cm from the eye. Find the nature, the focal length and the power of the correcting lens.

What is meant by overloading of an electrical circuit? Explain two possible causes due to which overloading may occur in the household circuit. Explain one precaution that should be taken to avoid the overloading of a domestic electric circuit.

i. Shruti draws magnetic field lines close to the axis of a current carrying circular loop. As she moves away from the centre of circular loop, she observes that the lines keep on diverging. Explain the reason for her observation.

ii. Write two properties of magnetic field lines.

“We are looking for an alternative or non-conventional source of energy.” State three reason for it.

i. Identify the acid and the base whose combination forms the common salt that you use in your food. Write the formula and chemical name of this salt. Name the source from where it is obtained.

ii. What is rock salt? Mention its colour and the reason due to which it has this colour.

iii. What happens when electricity is passed through brine? Write the chemical equation for it.

OR

i. Write the chemical name and chemical formula of washing soda.

ii. How is it obtained from sodium chloride? Give equations of the reactions.

iii. Why it is called a basic salt? Give its any one use.

An element placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide.

i. Identify the element.

ii. Write the electronic configuration.

iii. Write a balanced equation when it burns in the presence of air.

iv. Write a balanced equation when this oxide is dissolved in water.

v. Draw the electron dot structure for the formation of this oxide.

i. List the sequence of events that occur during the process of photosynthesis.

ii. List the three kinds of blood vessels of human circulatory system and write their functions in tabular form.

i. Write the functions of each of the following parts in a human female reproductive system:

A. Ovary B. Uterus

C. Fallopian tube

ii. Write the structure and functions of placenta in a human female.

i. Define the following terms in the context of spherical mirrors:

A. Pole

B. Centre of curvature

C. Principal axis

D. Principal focus

ii. Draw ray diagrams to show the principal focus of a:

A. Concave mirror

B. Convex mirror

iii. Consider the following diagram in which M is a mirror, P is an object and Q is its magnified image formed by the mirror.

State the type of the mirror M and one characteristic property of the image Q.

OR

i. Draw a ray diagram to show the formation of image by a convex lens when an object is placed in front of lens between its optical centre and principal focus.

ii. In the above ray diagram mark the object-distance (u) and the image-distance (v) with their proper signs (+ve or –ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.

iii. Find the power of a convex lens which forms a real, and inverted image of magnification-1 of an object placed at a distance of 20 cm from its optical center.

i. Two identical resistors each of resistance 10Ω are connected in

A. Series

B. Parallel to a 6 V battery

Calculate the ratio of power consumed in the combination of resistors in two cases.

ii. Draw the circuit diagram of the two cases.

Ans. i. 4 : 1

Rahul adds aqueous solution of barium chloride to an aqueous solution of sodium sulphate. What would he observe?

A strip of copper was placed in a beaker containing zinc sulphate solution. On observing the strip next day, was there any colour change in the strip?

To prepare a good temporary mount of the petunia leaf peel showing many stomata, from where does the student has to get the peel?

OR

A student sets up the apparatus for the experiment to show that CO₂ is released during respiration. After 2 hours, what would he observe?

Which of the following is not the correct diagram depicting budding in yeast?

A student carries out the experiment of tracing the path of a ray of light through a rectangular glass slab, for two different values of angle of incidence ∠i = 30° and ∠i = 45°. Find the set of values of the angle of refraction (∠r) and the angle of emergence (∠e), she is likely to observe in the two cases.

The following apparatus is available in a laboratory.

Find the best combination of voltmeter and ammeter for finding the equivalent resistance of the resistors in series.

Tap water conducts electricity whereas distilled water does not. Why?

An organic compound burns with a sooty flame. Is it a saturated or an unsaturated compound?

Explain why the planets do not twinkle.

Select the biodegradable items from the list given below.

Polythene bags, old clothes, wilted flowers, pencil shavings, glass bangles, bronze statue, vegetable peels.

How dud ‘Chipko Andolan’ ultimately benefit population? Give any two benefits.

A solution of a substance ‘X’ is used for white-washing.

i. Name the substance ‘X’ and write its formula.

ii. Write the reaction of the substance ‘X’ named in (i) above with water.

Explain the following statements:

i. Most metal oxides are insoluble in water but some of these dissolve in water. What are these oxides and their solutions in water called?

ii. At ordinary temperature, the surface of metals such as magnesium, aluminium and zinc, etc. is covered with a then layer. What is the composition of this layer? State its importance.

iii. Some alkali metals can be cut with a knife.

Give a reason why carbon can neither form C^{4 +} cations nor C^4— anxious, but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points.

i. What does the given experimental set-up demonstrate?

ii.

(a) Label the two parts indicated by Question marks and labelled 1 and 2 in the above diagram.

(b) Suggest a suitable caption or heading for the above diagram.

OR

What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

The genotype of green-stemmed tomato plants is denoted as GG and that of purple-stemmed tomato plants as gg. When these two are crossed,

i. What colour of stem would you expect in their F₁ progeny?

ii. Give the percentage of purple-stemmed plants if F₁ plants are self-pollinated.

iii. In what ratio would you find the genotypes GG and Gg in the F₂ progeny?

In one of his experiments with pea plants, Mendel observed that when a pure tall pea plant is crossed with a pure dwarf pea plant, in the first generation, F1 only tall plants appear.

i. What happens to the traits of the dwarf plants in this case?

ii. When the F1 generation plants were self-fertilised, he observed that in the plants of the second generation, F2 both tall plants and dwarf plants were present. Why it happened? Explain briefly.

A beam of white light falling on a glass prism gets split up into seven colours marked 1 to 7 as shown in the diagram.

A student makes the following statements about the spectrum observed on the screen.

i. The colours at positions marked 3 and 5 are similar to the colour of the sky and the core of a hard boiled egg respectively.

Is the above statement made by the student correct or incorrect? Justify.

ii. Which two positions correspond closely to the colour of

(a) a solution of potassium permanganate?

(b) ‘danger’ or stop signal lights?

OR

Describe the formation of rainbow in the sky with the help of a diagram.

Explain the meaning of the word ‘ electromagnetic’ and ‘induction’ in the term electromagnetic induction. On what factors does the value of induced current produced in a circuit depend state on practical application of this phenomenon in everyday life.

Explain the meaning of the word ‘ electromagnetic’ and ‘induction’ in the term electromagnetic induction. On what factors does the value of induced current produced in a circuit depend state on practical application of this phenomenon in everyday life.

What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?

A dry pallet common base ‘X’, when kept in open air absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify ‘X’. What type of reaction occurs when ‘X’ is treated with strong acid? Write a balanced chemical equation for such a reaction.

ii. Can we store the ‘X’ in an aluminium container? Give reason in support of your answer.

OR

Give a suitable reason for the following statements:

i. Rain water conducts electricity but distilled water does not.

ii. We feel burning sensation in the stomach when we overeat.

iii. A tarnished copper vessel regains its shine when rubbed with lemon.

iv. The crystals of washing soda change to white powder on exposure to air.

v. An aqueous solution of sodium chloride is neutral but an aqueous solution of sodium carbonate is basic.

In the following table, six elements A,B,C,D,E and F of the modern periodic table with atomic numbers 3 to 18 are given:

i. Which of these is (a) Noble gas, (b) halogen?

ii. Which of these is the most active metal in 3rd period?

iii. Identify the most electronegative element in the third period.

iv. In the compound between B and F, what type of bond will be formed?

v. What would be the nature of oxide formed by C?

It was observed that the leaves of a plant started getting wilted. Name the tissue which might have blocked. State the role of this tissue in plants.

ii. Explain opening and closing of stomata with the help of labelled diagrams.

iii. Name the physical phenomenon by which exchange of gasses occur between plant body and atmosphere.

i. Name the organ that produces sperms as well as secretes a hormone in human males. Name the hormone it secretes and write its functions.

ii. Name the parts of the human female reproductive system where fertilisation occurs.

iii. Explain how the developing embryo gets nourishment inside the mother’s body.

Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the Question s that follow, without doing any calculations:

i. What is the focal length of the convex lens? Give reason in support of your answer.

ii. Write the serial number of the observation which is not correct. How did you arrive at this conclusion?

iii. Take an appropriate scale to draw ray diagram for the observation at S.No.4 and find the approximate value of magnification.

OR

i. To construct a ray diagram we use two rays which are so chosen that it is easy to know their directions after reflection from the mirror. List two such rays and state the path of these rays after reflection in case of concave mirrors. Use these two rays and draw ray diagram to locate the image of an object placed between pole and focus of a concave mirror.

ii. A concave mirror produces three times magnified image on a screen. If the object is place 20 cm in front of the mirror, how far is the screen from the object?

i. For observation no.3 clearly shows that the focal length is + 15 cm.

(i) The electric power consumed by a device may be calculated by using either of the two expressions P = I2R or P = V2/R. The first expression indicates that it is directly proportional to R whereas the second expression indicates inverse proportionality. How can the seemingly different dependence of P on R in these expressions be explained?

ii. Explain the following:

(a) Why is tungsten used almost exclusively for filament of electric lamps?

(b) Why are copper and aluminium wires usually used for electricity transmission?

What happens when ferrous sulphate crystals are heated?

Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that the blue colour of the solution changes and a layer gets deposited or iron filings. What is the colour of the solution and the layer deposited?

Which light influences the opening of stomata?

In the slides showing binary fission in Amoeba and budding in yeast, what is it observed?

Study the ray diagram given below and answer the following Question s:

i. State the type of lens used in the figure.

ii. List two properties of the image formed.

iii. In which position of the object will the magnification be-1?

OR

A student obtains a blurred image of an object on a screen by using a concave mirror. In order to obtain a sharp image on the screen, in which direction he will have to shift the mirror?

Plot a graph which shows the dependence of current I on potential difference V across a resistor R.

During summer season, a milkman usually adds a very small amount of baking soda to fresh milk. Give one reason.

Name the functional group in the given compound: CH₃ CH₂ COOH

A person is able to see objects clearly only when these are lying at distances between 50cm and 300cm from his eye.

i. What kind of defects of vision he is suffering from?

ii. What kind of lenses will be required to increase his range of vision from 25cm to infinity? Explain briefly.

Given below is a picture of an ecosystem. Identify any two abiotic components and any two biotic components of this ecosystem.

Quote three instances where human intervention saved the forests from destruction.

i. Why potato chips manufacturers fill the packet of chips with nitrogen gas?

ii. A student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings.

OR

i. Crystals of copper sulphate are heated in a test for some time.

(a) What is the colour of copper sulphate crystals before heating, and after heating?

(b) What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process?

ii. A metal ‘X’ when dipped in an aqueous solution of aluminium sulphate no reaction is observed whereas when it is dipped in an aqueous solution of ferrous sulphate, the pale green solution turns colourless. Identify metal ‘X’ with reason.

State which of the following chemical reaction will take place, giving a suitable reason for each.

Zn(s)+CuSO₄(aq)→ ZnSO₄(aq) + Cu(s)

Fe(s)+ ZnSO₄(aq) → FeSO₄(aq)+Zn(s)

Zn(s)+ FeSO₄→ ZnSO₄+Fe(s)

What is a homologous series of carbon compounds? List its any two characteristic. Write the name and formula of next higher homologue of HCOOH.

Label parts 1 to 6 in the given figure of the brain.

i. Answer the following:

(a) Which hormone is responsible for the changes noticed in females at puberty?

(b) Dwarfism results due to deficiency of which hormone?

(c) Blood sugar level rises due to deficiency of which hormone?

(d) Iodine is necessary for the synthesis of which hormone?

(e) Which hormone controls the metabolism of calcium and phosphorus in human beings?

ii. Give an example of a plant hormone that promotes growth.

Study the given data and answer the questions following the data.

i. What is the term for this type of cross?

ii. What does the data of the column market F₁ indicate?

ii. Express the genotype of the (a) parent (b) F₁ Progeny and (c) F₂ Progeny

Give one term caption for the two pictures given here.

Define the term and give its signifance in evolution.

Suggest a reason for each of the following:

i. The sky near the horizon appears to have a reddish colour at the time of sunset and sunshine.

ii. The sun is visible to us two minutes before the actual sunrise and two minutes after the sunset.

i. In a household electric circuit different appliances are connected in parallel to one another. Give two reasons.

ii. An electrician puts a fuse of rating 5A in that part of domestic electrical circuit in which an electrical heater of rating 1.5 kW, 220 V is operating. What is likely to happen in this case and why? What change, if any, needs to be made?

You are given following current-time graphs from two different sources:

i. Name the type of current in two cases.

ii. Identify any one source for each type of these currents.

iii. What is the frequency of the current in case (b) in India?

iv. Use the above graphs to write two differences between the current in two cases.

i. Name two gases, other than carbon-dioxide, that is given out during the burning of fossil fuels and contributes towards acid rain formation.

ii. Out of two solar cookers, one was covered by a plane glass slab and the other was left open. Which of the two solar cookers will be more efficient and why?

OR

i. Why are many thermal power plants set up near coal or oil fields?

ii. Justify in one sentence that hydropower (hydel electricity) is a renewable source of energy.

i. A dry pallet of common base ’X’, when kept in open air absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify ‘X’. What type of reaction occurs when ‘X’ is treated with strong acid? Write a balanced chemical equation for such reaction.

ii. Can we store the base ‘X’ in an aluminium container? Give reason in support of your answer.

i. What were the two major shortcomings of Mendeleev’s periodic table? How have these been removed in the modern periodic table?

ii. Two elements X and Y have atomic numbers 12 and 16 respectively. Write the electronic configuration for these elements. To which period of the modern periodic table do these two elements belong? What type of bond will be formed between them and why?

i. Draw the diagram of a heart and label its four chambers.

ii. Construct a table to show the functions of these four chambers.

OR

Plants absorb water from the soil. How does this water reach the tree tops? Explain in detail.

i. What is pollination? Give its two types.

ii. Draw a longitudinal section of female reproductive part of a flower showing germination of the pollen grain. The label on it the following:

(a) Stigma;

(b) Pollen tube with a male germ cell;

(c) Female germ cell.

Draw ray diagrams to show the formation of a three times magnifier (i) real image (ii) virtual image of an object kept in front of a converging lens. Mark the positions of object, F, 2F, O and position of image clearly in the diagram.

An object of size 5 cm is kept at a distance of 25 cm from the optional centre of a converging lens of focal length 10cm. Calculate the distance of the image from the lens and size of the image.

A current of 1 ampere flows in a series circuit having an electric lamp and a conductor of 5 ohm when connected to a 10 V battery. Calculate the resistance of the electric lamp.

Now if a resistance of 10 ohm is connected in parallel with this series combination, what change (if any) in current flowing through 5 ohm conductor and potential difference across the lamp will take place? Give reason.

OR

B₁, B₂, B₃ are three identical bulbs connected as shown in the figure. Ammeters A₁, A₂, A₃ are connected as shown. When all the bulbs glow, the current of 3A is recorded by ammeter A.

i. What happens to the glow of the other two bulbs when bulb B₁ gets fused?

ii. What happens to the reading of A₁, A₂, A₃ and A when the bulb B₂ gets fused?

iii. How much power is dissipated in the circuit when all the three bulbs glow together?

When an iron rod is dipped into a solution of copper sulphate, copper is displaced. Why is it so?

Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that the blue colour of the solution changes and a layer gets deposited on iron filings. What is the colour of the solution and the layer deposited?

While preparing a temporary stained mount of an epidermal leaf peel, how is the extra stain removed?

The given slides A and B were identified by four students I, II III and IV as stated below:

I. Binary fission in Amoeba Daughter cells of Amoeba

II. Budding in yeast Buds of yeast

III. Binary fission in Amoeba Buds of yeast

IV. Budding in yeast Daughter cells of Amoeba

Of the above-mentioned identifications of slides A and B, which one is correct?

Find the focal length of the concave mirror in the experimental set-up shown in figure.

OR

In an experiment to trace the path of a ray of light passing through a rectangular glass slab, the angle of incidence in the air was given as 60°. Two students P and Q found the angle of refraction as 42° and 65° respectively. Who is right and why?

An ammeter has 20 divisions between mark 0 and mark 2 on its scale. Find the least count of the ammeter.