Concepts
Matter
The matter is the material of which everything in this universe, in and around us is made up of in different shapes. It is anything that occupies space and has mass and offers resistance to any applied force.
Physical Nature of Particles : Matter is made up of particles. The particles of matter are very-very small
Characteristics of Particles :
(i) Particles of matter are continuously moving i.e., they possess kinetic energy. As the temperature rises, particles moves faster because kinetic energy of the particles increases.
(ii) Particles of matter have space between them. When we make tea, coffee or lemonade (nimbu pani), particles of one type of matter get into the space between particles of the other. This shows that there is enough space between particles of matter.
(iii) Particles of matter attract each other. When we open a water tap, try to break the stream of water with your fingers, can we do this ? No, because the stream of water remains together. Particles of water are held together because of the force of attraction between them.
The space between the particles and kinetic energy of particles is minimum in solids, intermediate in liquids and maximum in gases.
The force of attraction between the particles is strongest in solids, intermediate in liquids and weakest in gases.
Movement of particles is minimum in solids, more in liquids and maximum in gases.
MCQs for Practice
Q (1): In which of the following conditions, the distance between the molecules of hydrogen gas would increase?
(i) Increasing pressure on hydrogen contained in a closed container.
(ii) Some hydrogen gas leaking out of the container.
(iii) Increasing the volume of the container of hydrogen gas.
(iv) Adding more hydrogen gas to the container without increasing the volume of the container.
( a ) (i) and (iii)
( b ) (i) and (iv)
( c ) (ii) and (iii)
( d ) (ii) and (iv)
Q (2): Name one property of liquids and gases which tells us that their molecules are moving constantly.
( a ) Diffusion
( b ) Dispersion
( c ) Diffraction
( d ) NONE
Q (3): To convert a temperature on Kelvin scale to the Celsius scale, how much do we have to subtract from the Kelvin temperature.
( a ) 270
( b ) 271
( c ) 272
( d ) 273
Q (4): Which of these is correct about solid carbon dioxide?
( a ) It is an extremely cold substance.
( b ) It is used to ‘deep freeze’ food.
( c ) It is used to keep ice-cream cold.
( d ) All are correct
Q. 5 Which one of the following sets of phenomena would increase on raising the temperature?
(a) Diffusion, evaporation, compression of gases
(b) Evaporation, compression of gases, solubility
(c) Evaporation, diffusion, expansion of gases
(d) Evaporation, solubility, diffusion, compression of gases
Q. 6 During summer, water kept in an earthen pot becomes cool because of the
phenomenon of
(a) diffusion
(b) transpiration
(c) osmosis
(d) evaporation
Q. 7 In which of the following conditions, the distance between the molecules of
hydrogen gas would increase?
(i) Increasing pressure on hydrogen contained in a closed container
(ii) Some hydrogen gas leaking out of the container
(iii) Increasing the volume of the container of hydrogen gas
(iv) Adding more hydrogen gas to the container without increasing the
volume of the container
(a) (i) and (iii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (ii) and (iv)
Q. 8 Choose the correct statement of the following
(a) conversion of solid into vapours without passing through the liquid
state is called sublimation.
(b) conversion of vapours into solid without passing through the liquid
state is called vapourisation..
(c) conversion of vapours into solid without passing through the liquid
state is called freezing.
(d) conversion of solid into liquid is called sublimation.
Q. 9 On converting 25°C, 38°C and 66°C to Kelvin scale, the correct sequence of temperature will be
(a) 298 K, 311 K and 339 K
(b) 298 K, 300 K and 338 K
(c) 273 K, 278 K and 543 K
(d) 298 K, 310 K and 338 K
Q. 10 Fill in the blanks: (5 Marks)
(a) Evaporation of a liquid at room temperature leads to a ______ effect.
(b) At room temperature the forces of attraction between the particles of solid substances are ______ than those which exist in the gaseous state.
(c) The arrangement of particles is less ordered in the ______ state. However, there is no order in the state.
(d) ______ is the change of gaseous state directly to solid state without going through the ______ state.
(e) The phenomenon of change of a liquid into the gaseous state at any temperature below its boiling point is called ______.
Solution:
(a) Cooling
(b) Stronger
(c) Liquid, gaseous
(d) Sublimation, liquid
(e) Evaporation
Q. 11 Classify the following into osmosis/diffusion:
(a) Swelling up of a raisin 9n keeping in water.
(b) Spreading of virus on sneezing.
(c) Earthworm dying on coming in contact with common salt.
(d) Shrinking of grapes kept in thick sugar syrup.
(e) Preserving pickles in salt.
(f) Spreading of smell of cake being baked throughout the house
(g) Aquatic animals using oxygen dissolved in water during respiration.
Solution:
(a) Osmosis
(b) Diffusion
(c) Osmosis
(d) Osmosis
(e) Osmosis
(f) Diffusion
(g) Diffusion
Q. 12 Water as ice has a cooling effect, whereas water as steam may cause severe burns. Explain these observations. (2 Marks)
Solution:
Water in the form of ice has low energy since water freezes at a lower temperature. When ice comes in contact with body it draws heat from the body and gives cooling effect. In case of steam, the water molecules have high energy. The high energy of steam is transformed as heat and may cause severe burns.
Q. 13.Alka was making tea in a kettle. Suddenly she felt intense heat from the puff of steam gushing out of the spout of the kettle. She wondered whether the temperature of the steam was higher than that of the water boiling in the kettle. Comment. (2 Marks)
Solution:
The temperature of both boiling water and steam is 100°C but steam has more energy because of latent heat of vaporisation. Hence, steam is hotter than boiling water.
Q. 14 Tabulate the differences in the characterisitcs of states of matter.
Q. 15 You want to wear your favourite shirt to a party, but the problem is that it is still wet after a wash. What steps would you take to dry it faster? (3 Marks)
Solution:
The process of drying the shirt can be made faster in the following ways :
(a) Spread the shirt to increase the surface area which will increase rate of evaporation.
(b) Put it in the sun to increase the temperature to increase the rate of evaporation.
(c) Keep it under the fan to increase the wind speed which increases the rate of evaporation.
Q. 16 Convert the following temperature to Fahrenheit scale: a. 3000 C b. 5730 c. -400C
Q. 17 Comment any 4 of the following: rigidity, compressibility, fluidity, filling a gas container, shape, kinetic energy and density (4 Marks)