Matter in Our Surroundings

Q83. State any two characteristic properties of a liquid.
Or
What are the main characteristics of a liquid?
Or
What are the characteristics of liquids?

Ans. Characteristics of liquids

a. Liquids have no fixed shape but have a fixed volume. 

b. They take up the shape of the container in which they are kept. 

c. Liquids flow and change shape, so they are not rigid but can be called fluid.

Q84. Name two gases of air which dissolve in water by diffusion. What is the importance of this process in nature?
Or
What is the importance of diffusion of gases in water in nature?

Ans. The gases from the atmosphere diffuse and dissolve in water. These gases, especially oxygen and carbon dioxide, are essential for the survival of aquatic animals and plants. All living creatures need to breathe for survival. The aquatic animals can breathe under water due to the presence of dissolved oxygen in water.

Q85. Why are gases so easily compressible whereas it is almost impossible to compress a solid or a liquid?

Ans. This so because the spaces in between the constituent particles are minimum in the case of solids, intermediate in liquids and maximum in gases. On applying pressure, the gaseous particles come together, where as in liquids and solids, the particles are very close and hence cannot be further brought closer. Hence gases are compressible but not liquids and solids.

Q86. A piece of chalk can be broken into small particles by hammering but a piece of iron cannot be broken into small particles by hammering. Why?

Ans. Particles of matter have force acting between them. This force keeps the particles together. The strength of this force of attraction varies from one kind of matter to another. A chalk piece can be broken easily but not an iron piece because as compared to chalk, iron has greater intermolecular force of attraction which keeps the particles together. 

Q87. What are the characteristics of the particles of matter?

Ans. The important characteristics of the particles of matter are the following:

1. Particles of matter have space between them. 

2. Particles of matter are continuously moving.

3. Particles of matter attract each other. 

4. Particles of matter are very, very small.

Q88. Give two reasons to justify—
(a) water at room temperature is a liquid.
(b) an iron almirah is a solid at room temperature.

Ans. (a) Transition in the states of matter of water occurs at 0°C and 100°C. The room temperature is around 20–25°C. Hence, water at room temperature is a liquid.

(b) The melting point of iron is 1,538°C and boiling point is 2,862°C. The room temperature is around 20–25°C. Thus, an iron almirah is a solid at room temperature.

Q89. What happens when a crystal of potassium permanganate is dropped in a glass tumbler containing water? What conclusion can you draw?

Ans. This experiment shows that just a few crystals of potassium permanganate can colour a large volume of water (about 1000 L). So we conclude that there must be millions of tiny particles in just one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles. Ultimately a stage is reached when the particles cannot divide further into smaller particles.

Q90. Arrange the following substances in increasing order of forces of attraction between the particles— water, sugar, oxygen.

Ans. There are some forces of attraction between the particles of matter which bind them together. The force of attraction is different in the particles of different kinds of matter. The force of attraction is maximum in the particles of solid matter and minimum in the particles of gaseous matter.

Thus, the increasing order of forces of attraction between the particles of water, sugar and oxygen is Oxygen<Water<Sugar.

Q91. Among solids, liquids and gases, which one has: (a) maximum force of attraction between the particles? (b) minimum spaces in between particles? (c) maximum movement of particles?

Ans. (a) The forces of attraction between the particles are maximum in solids, intermediate in liquids and minimum in gases.

(b) The spaces in between the constituent particles are minimum in the case of solids, intermediate in liquids and maximum in gases.

(c) The kinetic energy of the particles is minimum in the case of solids, intermediate in liquids and maximum in gases.