Question

(a) Chalk and aluminium foil usually look different from each other. Give a property by which we can prove that these materials are different. [1 mark]

(b) Metals have lustre (shine). Give a reason why some metal articles become dull and lose their shine after some time. [1 mark]

(c) Mixtures of red chilli powder in water, butter in water, petrol in water, and vinegar in water were given to Radha, Sudha, Sofia and Raveena, respectively. Whose mixture is in solution form?​ [1 mark]

(d) During the summer holidays, a group of children collected a small thermocol box and a piece of sugar candy (mishri) and tried to group them on the basis of properties such as floatation and solubility in water by making a table. What would that table look like? [2 marks]

Answer 1

(a) Chalk and aluminium foil can be differentiated using the property of lustre (shine). Aluminium foil is lustrous whereas chalk is non-lustrous. [1 mark]

(b) Metals when exposed to air react with the moisture and gases present in it and form a dull layer of some other substance on it, thereby becoming dull and losing their shine. [1 mark]

(c) Raveena will get the mixture in solution form because vinegar is soluble in water but red chilli powder, butter and petrol are not soluble in water and hence, they do not form a solution. [1 mark]

(d) A small thermocol box and a piece of sugar candy (mishri) can be classified based on floatation and solubility in water as follows:

	Thermocol box	Sugar candy (mishri)
Floatation in water	Floats [0.5 marks]	Sinks [0.5 marks]
Solubility in water	Insoluble [0.5 marks]	Soluble ​​​​​​​[0.5 marks]