Ans. A diver is able to cut through water in a swimming pool. This shows that the particles (or molecules) in water are not tightly packed, they are somewhat loose, having spaces between them.
Ans. Density of ice is less than density of water. The low density of ice is due to its structure. The molecules in ice make a cage like structure with lot of vacant spaces; this makes ice float on water.
Ans. The force of attraction between the particles of honey is more than the force of attraction between the particles of water. The particles are strongly bonded in honey than water. Thus, honey is more viscous than water.
Ans. Intermixing of particles of two different types of matter on their own is called diffusion. Example: When perfume is sprayed in one part of a room, it spreads to the rest through diffusion.
Ans. The forces of attraction between the particles are minimum in gases and the particles move about randomly at high speed. Due to the movement of particles with high speed gas diffuses most rapidly.
Ans. When we dissolve salt in water, the particles of salt get into the spaces between particles of water. Hence, there is no increase in the volume. This shows that there is enough space between particles of matter.
Ans. (a) At 250°C, water exists in the gaseous state.
(b) At 100°C, water can exists as both liquid and gas. At this temperature, water starts changing from its liquid states to its gaseous (vapour) state.
Ans. The temperature remain constant during the melting of ice even though heat is supplied continuously because this heat gets used up in changing the state by overcoming the forces of attraction between the particles.
Ans. Particles in steam, that is, water vapour at 373 K (100°C) have more energy than water at the same temperature. This is because particles in steam have absorbed extra energy in the form of latent heat of vaporisation.
Ans. Matter around us exists in three different states–
a. solid - chalk
b. liquid - water
c. gas - air
Ans. This shows 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.
Ans. The temperature remain constant during the boiling of water even though heat is supplied continuously because this heat gets used up in changing the state by overcoming the forces of attraction between the particles.
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