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Which of the following statements are true for pure substances?
(i) pure substances contain only one kind of particles
(ii) pure substances may be compounds or mixtures
(iii) pure substances have the same composition throughout
(iv) pure substances can be exemplified by all elements other than nickel
Two chemical substances X and Y combine together to form a product P which contains both X and Y
X + Y → P
X and Y cannot be broken down into simpler substances by simple chemical reactions. Which of the following statements concerning X, Y and P are correct?
(i) P is a compound
(ii) X and Y are compound
(iii) X and Y are elements
(iv) P has a fixed composition
Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.
(a) What type of substance is B?
(b) What type of substance is C?
(c) Name the gas (i) D, and (ii) E?
(d) Write one characteristic property of gas D.
There are three substances X, Y and Z. The substance X does not have a fixed melting point or boiling point and it still shows the individual properties of its constituents. The substance Y is a pure substance which occurs in nature as such. The substance Y has a fixed melting point and boiling point but it cannot be broken down into simpler substances by any chemical means. The substance Z is also a pure substance whose properties are entirely different from those of its constituents. The substance Z can, however, be divided by electrolysis into two substances which belong to the same class of substances as Y.
(a) What type of substance could X be? Name one substance like X.
(b) What type of substance could Y be? Name one substance like Y.
(c) What type of substance could Z be? Name one substance like Z.
(d) Whish process involves absorption or release of an appreciable amount of energy: formation of substance X or formation of substance Z?
(e) Name the three groups into which all the substances like Y are divided on the basis of their properties.
There is a large group of materials P which can be divided into three groups Q, R, and S on the basis of their properties. The substances belonging to group Q can be solids, liquids or gases. The solids belonging to group Q are usually electrical insulators. Most of the substances of group R are solids which are good conductors of electricity. The substances belonging to group S are neither insulators like Q nor good conductors like R. The properties of S are intermediate between those of Q and R.
(a) What could the group of materials P be?
(b) Name the substances Q. Give two examples of such substances.
(c) Name the substances R. Write two examples of such substances.
(d) Name the substances S. Give two examples of such substances.
(e) Out of Q, R and S, which substances are malleable and ductile?
A, B and C are all liquids. Liquid A has a comparatively low boiling point. On heating, liquid a vaporizes completely without leaving behind any residue. Liquid A is being used increasingly as a fuel in motor vehicles either alone or by mixing with petrol. Liquid B has a very high boiling point. It also vaporizes completely on heating, without leaving any residue. Liquid B is a conductor of electricity and used in making thermometers. Liquid c has a moderate boiling point. On heating, liquid C vaporises leaving behind a white solid D which is used in cooking vegetables. The condensation of vapours from C give a liquid E which turns anhydrous CuSO4 to blue.
(a) Which liquid could be an element? Name this element.
(b) Which liquid could be a mixture? Name this mixture.
(c) Which liquid could be a compound? Name this compound.
(d) What could the solid D be?
(e) What do you think is liquid E?
Three mixtures A, B and C are obtained by stirring three different solids in water taken in separate beakers. When mixture A is allowed to stand for some time, then its particles settle at the bottom of the beaker. When a beam of light is passed through mixture A in a dark room, the path of light becomes visible when observed from the side of the beaker. When mixture B is allowed to stand for a considerable time, even then its particles do not settle down. Mixture B, however, scatters the beam of light just like mixture A. The particles of mixture C do not settle down on keeping and it also does not scatter a beam of light passing through it.
(a) What are the mixtures like A known as?
(b) What are the mixtures like B known as?
(c) What are the mixtures like C known as?
(d) Name the phenomenon exhibited by A and B which occurs on passing a beam of light through them.
(e) Name one mixture each which is like (i) A (ii) B, and (iii) C.
When the solid A is added to water, it dissolves with the evolution of a lot of heat and making little explosions to form two products B and C. The properties of products B and C are entirely different from those of solid A as well as water. Moreover, products B and C cannot be reconverted into solid A and water. When another solid D is added to water, it dissolves with the absorption of a little heat to form a product E which cools down. The product E shows the properties of both, solid D as well as water. Moreover, product E can be converted into solid D and water.
(a) What type of change occurs when solid A is dissolved in water? Why?
(b) What type of change occurs when sold D is dissolved in water? Why?
(c) Name a metal which you think could behave like solid A. Also name the products B and C.
(d) Name the solid D if it is the one which is used in making ordinary dry cells.
(e) Name the process by which D can be recovered from E.
100 ml of water at room temperature of 25°C is taken in a beaker and a little of solid S is dissolved in it by stirring to obtain a solution X. More and more of solid S is added to the solution with constant stirring, while keeping the temperature of solution constant at 30°C. After some time it is observed that no more solid dissolves in water and at the same time some solid is also left undissolved at the bottom of the beaker. The contents of beaker are filtered through a filter paper to obtain solution Y in the form of a filtrate.
(a) What name is given to solutions like X?
(b) What name is given to solution like Y?
(c) What will you observe if the solution Y at 30°C is cooled down to 10°C by keeping the beaker in crushed ice? Why?
(d) What term is used to denote the amount of solid dissolved in 100 grams of water in a solution like Y?
Fill in the following blanks with suitable words:
(a) Miscible liquids are separated by ……….. .
(b) Immiscibl liquids are separated by using a ………….. .
(c) A mixture of kerosene and petrol can be separated by ………… .
(d) The separation of liquids by fractional distillation is based o the difference in their ………….. .
(e) The gases of air can be separated by fractional distillation of liquid air because they have different ………… .
(f) A heterogeneous mixture of liquid and solid is conveniently separated by …….. .
(g) If a mixture contains iron filings as one of the constituents, if can be separated by using a …………. .
The liquid air has three components X, Y and Z whose boiling points are : -186C, -183C and -196C, respectively. When liquid air is fed into a tall fractional distillation column from near its bottom and warmed up slowly:
(a) Which component will be collected from near the bottom of the fraction distillation column? Why?
(b) Which component will be collected from the top part of the fractional distillation column? Why?
(c) Which component will be collected from the middle part of the fractional distillation column? Why?
(d) What could the component X, Y and Z be?
There are three liquids A, B and C, all having different densities and different boiling points. Liquids A and C are organic in nature whereas liquid B is considered to be inorganic. When liquids A and B are put together in a container, they form a single layer. On the other hand, when liquids B and C are mixed, they form two separate layers:
(a) Which process will you use to separate a mixture of A and B?
(b) Which method will you use to separate a mixture of B and C?
(c) Name the liquids which would behave like (i) a (ii) B and (iii) C.
A solid mixture contains four constituents P, Q, R and S. P consists of tiny grains and it is mixed with cement for plastering the walls. Q is a white solid which is recovered on a large scale from sea water by the process of evaporation. R is in the form of tiny particles of a material whose corrosion is called rusting. And S is a white solid which is used in making ordinary dry cells.
(a) What could P, Q, R and S be?
(b) How would you separate a mixture containing P, Q, R and S?
Tincture of iodine is a mixture of two materials X and Y. The material Y has a property that its solid form can be converted directly into vapours on heating by a process called Z.
(a) What could X be?
(b) What could Y be?
(c) Name the process Z.
(d) Which process would you use to recover both the components X and Y from tincture of iodine?
(e) Which process can be used to recover only component Y from tincture of iodine?
The given mixture contains three constituents A, B and C. The constituent A is a yellow coloured, solid element which dissolves in a liquid D. The constituents B is a blue coloured salt which is insoluble in liquid D but dissolves easily in another liquid E. The constitudent C is a liquid wlich is used in coolking food and forms a solid fat on hydrogenation.
(a) What do you think could (i) constituent A, and (ii) liquid D be?
(b) What could (i) constituent B, and (ii) liquid E be?
(c) What could liquid C be?
(d) How will you separate the mixture containing A, B and C.