Chemistry Chapter 1
1. What are the characteristics of the particles of matter?
Solution:
The characteristics of particles of matter are as follows:
(a) Presence of intermolecular spaces between particles
(b) Particles are in constant motion
(c) They attract each other
(d) All matter is composed of very small particles which can exist independently.
Q2. Differentiate Solid, Liquid & gas?
Solution:
The difference in the characteristics of the three states of matter
Convert the following temperature to Celsius scale:
a. 300K b. 573K
Solution:
a. 0°C=273K
300K= (300-273)°C = 27°C
b. 573K= (573-273)°C = 300°C
What is the physical state of water at:
a. 250°C b. 100°C ?
Solution:
(a) At 250°C – Gaseous state since it is beyond its boiling point.
(b) At 100°C – It is at the transition state as the water is at its boiling point. Hence it would be present in both liquid and gaseous states.
4. For any substance, why does the temperature remain constant during the change of state?
Solution:
It is due to the latent heat as the heat supplied to increase the temperature of the substance is used up to transform the state of matter of the substance; hence, the temperature stays constant.
5. Give reason for the following observations:
(a) Naphthalene balls disappear with time without leaving any solid.
(b) We can get the smell of perfume while sitting several metres away.
Solution:
(a) At room temperature, naphthalene balls undergo sublimation wherein they directly get converted from a solid to a gaseous state without having to undergo the intermediate state, i.e., the liquid state.
(b) Molecules of air move at a higher speed and have large intermolecular spaces. Perfumes comprise substances that are volatile, which scatter quickly in air, becoming less concentrated over a distance. Hence, we are able to smell perfume sitting several metres away.
6. Arrange the following in increasing order of forces of attraction between the particles – water, sugar, oxygen.
Solution:
Oxygen (gas) < water (liquid) < sugar (solid)
7. Why is ice at 273K more effective in cooling than water at the same temperature?
Solution:
At 273 K, ice will absorb heat energy or latent heat from the medium to overcome fusion and transform into water. As a result, ice has a greater cooling impact than water at the same temperature since water does not absorb the excess heat from the medium.
8. What produces more severe burns, boiling water or steam?
Solution:
Steam produces severe burns. It is because it is an exothermic reaction that releases a high amount of heat which it had consumed during vaporization.
9. Name A, B, C, D, E and F in the following diagram showing a change in its state.
Solution:
Interconversion of three states of matter: Using temperature or pressure, any state of matter can be turned into another.
(A) Solid to Liquid → Melting (or) fusion (or) liquefaction
(B) Liquid to Gas → Evaporation (or) vaporization
(C) Gas to liquid → Condensation
(D) Liquid to Solid → Solidification
(E) Solid to Gas → Sublimation
(F) Gas to Solid → solidification
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