Solution of Chapter (NCERT Science Exemplar Book)

On converting 25°C, 38°C and 66°C to kelvin scale, the correct answer will be

Choose the correct statement of the following

Rusting of an article made up of iron is called

Which of the following are homogeneous in nature?

(i) ice (ii) wood (iii) soil (iv) air

Following are a few definitions of osmosis. Read carefully and select the correct definition

Which among the following has specialised tissue for conduction of water?

Which of the following is not a criterion for classification of living organisms?

Which of the following is not important for individual’s health?

Chromosomes are made up of

A particle is moving in a circular path of radius (r). The displacement after half a circle would be

In case of negative work the angle between the force and displacement is

An object moving at a speed greater than that of sound is said to be moving at

Before playing the orchestra in a musical concert, a sitarist tries to adjust the tension and pluck the string suitably. By doing so, he is adjusting

Ozone - layer is getting depleted because of

To solve the food problem of the country, which among the following is necessary?

Which one of the following nutrients is not available in fertilizers?

A student heats a beaker containing ice and water. He measures the temperature of the contents of the beaker as a function of time. Which of the following would correctly represent the result? Give justification for your choice.

An element is sonorous and highly ductile. Under which category would you classify this element? What other characteristics do you expect the element to possess?

What information do you get from the following figures about the valency, atomic number and mass number of atoms X, Y and Z? Give your answer in a tabular form.

One electron is present in the outer most shell of the atom of an element X. What would be the nature and value of the charge on the ion formed if this electron is removed from the outer most shell?

Cells of onion peel and RBC are separately kept in hypotonic solution, what among the following will take place? Explain the reason for your answer.

(a) Both the cells will swell.

(b) RBC will burst easily while cells of onion peel will resist the bursting to some extent.

(c) a and b both are correct

(d) RBC and onion peel cells will behave similarly.

Name the different components of xylem and draw a living component of it.

Classify the following organisms based on the absence/presence of true coelom (i.e. acoelomate, pseudocoelomate and coelomate)

Spongilla, Sea anemone

Planaria, Liver fluke

Wuchereria, Ascaris

Nereis, Scorpion

Earthworm, Birds

Fishes, Horse

Which cell organelle controls most of the activities of the cell?

Draw well labeled diagrams of various types of muscles found in human body.

The following velocity-time graph shows the motion of a cyclist. Find (i) its acceleration, (ii) its velocity and (iii) the distance covered by the cyclist in 15 seconds.

A ball is dropped from a height of 10 m. If the energy of the ball reduces by 40% after striking the ground, how much high can the ball bounce back?

Draw a graph for a wave representing wave disturbance and time for a sound changing from low pitch to high pitch, keeping the amplitude of the sound same.

Why lichens do not occur in Delhi whereas they commonly grow in Manali or Darjeeling?

Lichens are called pioneer colonisers of bare rock. How can they help in formation of soil?

What is a GM crop? Name any one such crop which is grown in India.

If there is low rainfall in a village throughout the year what measures will you suggest to the farmers for better cropping?

In agricultural practices, higher input gives higher yield. Discuss how?

The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare this value with the mass of the Earth (5.98 × 10²⁴kg). Which one of the two is heavier and by how many times?

OR

In photosynthesis, 6 molecules of carbon dioxide combine with an equal number of water molecules through a complex series of reactions to give a molecule of glucose having a molecular formula C₆H₁₂O₆. How many grams of water would be required to produce 18 g of glucose? Compute the volume of water so consumed assuming the density of water to be 1 g cm^–3.

Explain giving reasons

(a) Balanced diet is necessary for maintaining healthy body.

(b) Health of an organism depends upon the surrounding environmental conditions.

(c) Our surrounding area should be free of stagnant water.

(d) Social harmony and good economic conditions are necessary for good health.

OR

Why is AIDS considered to be a ‘Syndrome’ and not a disease?

(a) Explain the meaning of inertia with the help of an example.

(b) Two balls of same size but of different materials, rubber and iron are kept on the smooth floor of a moving train. The brakes are applied suddenly to stop the train. Will the balls start rolling? If so, in which direction? Will they move with the same speed? Give reasons for your answer.

OR

(a) A ball of mass m is thrown vertically upward from the ground with an initial speed v, its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed v again before striking the ground. It implies that the magnitude of initial and final momentum of the ball are same. Yet, it is not an example of conservation of momentum. Explain why?

(b) A bullet of mass 20 g is horizontally fired with a velocity 150 m s^–1 from a pistol of mass 2 kg. What is the recoil velocity of the pistol?

(a) With the help of Second Law of Motion and the Universal Law of Gravitation derive an expression for acceleration due to gravity ‘g’.

(b) The weight of any person on the moon is about 1/6 times that on the earth. He can lift a mass of 15 kg on the earth. What will be the maximum, mass, which can be lifted by the same force applied by the person on the moon?

OR

(a) Identical packets are dropped from two aeroplanes, one above the equator and the other above the north pole, both at height ‘h’. Assuming all conditions are identical, will these packets take same time to reach the surface of the earth? Justify your answer.

(b) It is seen that a falling apple is attracted towards the earth. Does the apple also attract the earth? If so, we do not see the earth moving towards the apple. Why?

A motor car, with its glass totally closed, is parked directly under the sun. The inside temperature of the car rises very high. Explain why?

OR

What are the causes of water pollution? Discuss how can you contribute in reducing the water pollution.

Seema visited a Natural Gas Compressing Unit and found that the gas can be liquefied under specific conditions of temperature and pressure. While sharing her experience with friends she got confused. Help her to identity the correct set of conditions.

Which of the following are physical changes?

(i) Melting of iron metal

(ii) Rusting of iron

(iii) Bending of an iron rod

(iv) Drawing a wire of iron metal

Which one of the following has maximum number of atoms?

In a sample of ethyl ethanoate (CH₃COOC₂H₅) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?

A cell will swell up if

Survival of plants in terrestrial environment has been made possible by the presence of

In which group of animals coelom is filled with blood?

Organisms without nucleus and cell organelles belong to

Which cells do not have perforated cell walls?

The numerical ratio of displacement to distance covered by a moving object is

According to the third law of motion, action and reaction

The value of acceleration due to gravity

The gravitational force between two objects is F. If the masses of both objects are halved without changing distance between them, then the gravitational force would become

Among the given options, which one is not correct for the use of large amount of fertilisers and pesticides?

Find out the correct sentence

(i) Hybridization means crossing between genetically dissimilar plants.

(ii) Cross between two varieties is called as inter specific hybridisation.

(iii) Introducing genes of desired character into a plant gives genetically modified crop.

(iv) Cross between plants of two species is called as inter varietal.

Find out the correct sentence about manure

(i) Manure contains large quantities of organic matter and small quantities of nutrients.

(ii) It increases the water holding capacity of sandy soil.

(iii) It helps in draining out of excess of water from clayey soil.

(iv) Its excessive use pollutes environment because it is made of animal excretory waste.

‘Osmosis is a special kind of diffusion’ comment.

Give the chemical formulae for the following compounds and compute the ratio by mass of the combining elements in each one of them.

(a) Ammonia

(b) Carbon monoxide

(c) Hydrogen chloride

(d) Aluminum fluoride

Write the molecular formulae for the following compounds

(a) Aluminum (III) nitrate

(b) Calcium (II) phosphate

(c) Mercury (II) chloride

(d) Magnesium (II) acetate

Helium atom has 2 electrons in its valence shell but its valency is not 2, Explain.

If a person takes concentrated solution of salt. After sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.

Differentiate the following activities on the basis of voluntary or involuntary muscles.

(a) Jumping of frog

(b) Pumping of the heart

(c) Writing with hand

(d) Movement of chocolate in your intestine

Water hyacinth float on water surface. Explain.

Which bacterium causes peptic ulcers? Who discovered the above pathogen for the first time?

Give reasons for

(a) Meristematic cells have a prominent nucleus and dense cytoplasm but they lack vacuole.

(b) Intercellular spaces are absent in sclerenchymatous tissues.

(c) We get a crunchy and granular feeling, when we chew pear fruit.

(d) Branches of a tree move and bend freely in high wind velocity.

A motorcyclist drives from point A to point B with a uniform speed of 30 km h^–1 and returns back to point A with a uniform speed of 20 km h^–1. Find the average speed of the motorcyclist.

Velocity versus time graph of a ball of mass 50 g rolling on a concrete floor is shown below. Calculate the acceleration and the frictional force of the floor on the ball?

The volume of a 500 g sealed packet is 350 cm³. Will the packet float or sink in a saturated salt solution, if the density of the solution is 1.2 g cm^–3?

What will be the mass of the solution displaced by this packet?

Why step farming is common in hills?

Fertile soil has lots of humus. Why?

List out some useful traits in improved crop.

Arrange these statements in correct sequence of preparation of green manure.

(a) Green plants are decomposed in soil.

(b) Green plants are cultivated for preparing manure or crop plant parts are used.

(c) Plants are ploughed and mixed into the soil.

(d) After decomposition it becomes green manure.

An Italian bee variety Apis mellifera has been introduced in India for honey production. Write about its merits on other varieties.

A group of students took an old shoe box and covered it with a black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the sample taken in a beaker/glass tumbler as shown in the figure. They were amazed to see that milk taken in the glass was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it

(a) Explain why the milk sample was illuminated. Name the phenomenon involved.

(b) Same results were not observed with a salt solution. Explain.

(c) Can you suggest two more solutions which would show the same effect as shown by the milk solution?

OR

During an experiment the students were asked to prepare a 10% solution of sugar in water. Ramesh dissolved 10g of sugar in 100g of water while Sarika prepared it by dissolving 10g of sugar in water to make 100g of the solution.

(a) Are the two solutions of the same concentration?

(b) Compare the mass % of the two solutions.

Why do some children fall ill more frequently than others living in the same locality?

OR

Give any four factors necessary for a healthy person.

Define power. How will you differentiate between kW and kW h? If the velocity of a ball is tripled, what will be the ratio of

(a) its initial kinetic energy and final kinetic energy

(b) initial momentum and final momentum.

OR

Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it.

(a) How much work the men do in lifting the box?

(b) How much work do they do in just holding it?

(c) Why do they get tired while holding it? (g = 10 m s^–2)

(a) Explain how ‘echo’ is produced.

(b) What should be the minimum distance between the listener and the reflector to hear an echo of sound propagating with a speed v m s^–1?

(c) Does the speed of sound increase or decrease on a hotter day? Justify.

OR

Establish the relationship between speed of sound, its wavelength and frequency. If speed of sound in air is 340 m s^–1, calculate.

(a) wavelength when frequency is 256 Hz.

(b) frequency when wavelength is 0.85 m.

How do fossil fuels cause air pollution?

OR

Explain the role of the Sun in the formation of soil.