Chapter 2: Is Matter around Us Pure?

Name the process associated with the following

(a) Dry ice is kept at room temperature and at one atmospheric pressure.

(b) A drop of ink placed on the surface of water contained in a glass spreads throughout the water.

(c) A potassium permanganate crystal is in a beaker, and water is poured into the beaker with stirring.

(d) An acetone bottle is left open, and the bottle becomes empty.

(e) Milk is churned to separate cream from it.

(f) Settling of sand when a mixture of sand and water is left undisturbed for some time.

(g) Fine beam of light entering through a small hole in a dark room illuminates the particles in its paths

You are given two samples of water labelled as ‘A’ and ‘B’. Sample ‘A’ boils at 100°C, and sample ‘B’ boils at 102°C. Which sample of water will not freeze at 0°C? Comment.

What are the favourable qualities given to gold when it is alloyed with copper or silver for the purpose of making ornaments?

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?

Give an example, each for the mixture having the following characteristics. Suggest a suitable method to separate the components of these mixtures

(a) A volatile and a non-volatile component.

(b) Two volatile components with appreciable differences in boiling points.

(c) Two immiscible liquids.

(d) One of the components changes directly from a solid to a gaseous state.

(e) Two or more coloured constituents soluble in some solvent.

Fill in the blanks

(a) A colloid is a ——— mixture, and its components can be separated by the technique known as ———.

(b) Ice, water and water vapour look different and display different —— properties, but they are ——— the same.

(c) A mixture of chloroform and water taken in a separating funnel is mixed and left undisturbed for some time. The upper layer in the separating funnel will be of——— and the lower layer will be that of ———.

(d) A mixture of two or more miscible liquids, for which the difference in the boiling points is less than 25 K, can be separated by the process called———.

(e) When light is passed through water containing a few drops of milk, it shows a bluish tinge. This is due to the ——— of light by milk, and the phenomenon is called ——— . This indicates that milk is a ——— solution.

Sucrose (sugar) crystals obtained from sugarcane and beetroot are mixed together. Will it be a pure substance or a mixture? Give reasons for the same.

Give some examples of the Tyndall effect observed in your surroundings?

Can we separate alcohol dissolved in water by using a separating funnel? If yes, then describe the procedure. If not, explain.

On heating, calcium carbonate gets converted into calcium oxide and carbon dioxide.

(a) Is this a physical or a chemical change?

(b) Can you prepare one acidic and one basic solution by using the products formed in the above process?

If so, write the chemical equation involved