Chapter 02 Is matter around us pure

1. What is meant by a pure substance?

Answer

A pure substance consists of single type of particles that is all the constituent particles of a pure substance have same chemical nature. 

2. List the points of differences between homogeneous and heterogeneous mixtures.
Answer

Homogeneous mixtures

Heterogeneous mixtures

Homogeneous mixtures have uniform composition.

Heterogeneous mixtures have non uniform composition.

It has no visible boundaries of separation between its constituents.

It has visible boundaries of separation between its constituents.

1. Differentiate between homogeneous and heterogeneous mixtures with examples.
Answer
A homogeneous mixture is a mixture having a uniform composition throughout the mixture. For example, mixtures of salt in water, sugar in water, copper sulphate in water, iodine in alcohol, alloy, and air have uniform compositions throughout the mixtures.
On the other hand, a heterogeneous mixture is a mixture having a non-uniform composition throughout the mixture. For example, composition of mixtures of sodium chloride and iron fillings, salt and sulphur, oil and water, chalk powder in water, wheat flour in water, milk and water are not uniform throughout the mixtures.

2. How are sol, solution and suspension different from each other?
Answer

Sol

Solution

Suspension

They are heterogeneous in nature.

They are homogeneous in nature.

They are heterogeneous in nature.

They scatter a beam of light and hence show Tyndall effect.

They do not scatter a beam of light and hence do not show Tyndall effect

They do not scatter a beam of light and hence do not show Tyndall effect.

They are quite stable.

Examples of solution are: salt in water, sugar in water.

Examples of suspension are: sand in water, dusty air

3. To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Answer
Mass of solute (sodium chloride) = 36 g (Given)
Mass of solvent (water) = 100 g (Given)
Then, mass of solution = Mass of solute + Mass of solvent
= (36 + 100) g
= 136 g