3/Answer the following questions
(a) Give one example of diffusion.
(b) Why do gases have no definite shape and fixed volume?
(c) Why does diffusion get faster with a rise in temperature?
(d) 'Osmosis is a special kind of diffusion'. Comment
(e) The boiling point of water is much higher than that of petroleum ether. In which of the two, the intermolecular
forces are strong?
(f) Why are solids rigid and incompressible?
(g) Why does icecream appear cooler to the teeth than ice-cold water?
(h) A diver is able to cut through water in a swimming pool. Which property of matter does this observation
show?
(i) How does the water kept in an earthen pot (matka) become cool during summer?
j) Give two reasons to justify the following:
(i) Water at room temperature is a liquid.
(ii) An iron almirah is a solid at room temperature.
(k) Give two applications of evaporation.
Answers
Answer:
Explanation:
A. eg. Of diffusion - land breeze and see breeze.
B. Gases have no fixed shape and volume bcoz the particles of gas have negligible intermolecular force of attraction , due to which they are not packed as solids and they are scattered around the environment.
C. Diffusion increases with the increase in temperature bcoz with temp increase the kinetic energy of the particles increases and which increases the diffusion rate.
D. Osmosis is a special type if diffusion bcoz in osmosis the water moves from high concentration to lower concentration just as in diffusion. But diffusion is mainly for gases and osmosis for liquids.
Osmosis is of three types. :
a. Hypotonic
B. Isotonic
C. Hypertonic.
E. Since the b.p. of water is more than petroleum ether, this concludes that water has stronger intermolecular forces. Water has hydrogen bonding. So the b.p is more than petroleum ether.
F. The solids have strong intermolecar forces of attraction which makes them solid and rigid. And incompressible.
I. The water in earthen pot experiences evaporation due to which the water is cool. Evaporation leads to the loss of energy of the particles around making it cooler.
Answer:
(A) Examples of Diffusion. Perfume is sprayed in one part of a room, yet soon it diffuses so that you can smell it everywhere. A drop of food coloring diffuses throughout the water in a glass so that, eventually, the entire glass will be colored. After lighting a cigarette, the smoke spreads to all parts of a room.
(B) A gas is a substance with no definite volume and no definite shape. Solids and liquids have volumes that do not change easily. A gas, on the other hand, has a vol- ume that changes to match the volume of its container. The molecules in a gas are very far apart compared with the molecules in a solid or a liquid.
(C) Faster diffusion will take place if the surroundings are warmer. Increase in temperature means an increase in molecules' speed (kinetic energy). So the molecules move faster and there will be more spontaneous spreading of the material which means that diffusion occurs more quickly.
(D) The movement of particles from low concentration to high concentration is responsible for the diffusion in liquids and gases. In the case of osmosis the particles move from the low concentration to high concentration through the semi permeable membrane, this happens because of diffusion.
(F) Solids are rigid because the intermolecular forces of attraction that are present in solids are very strong. The constituent particles of solids cannot move from their positions they can only vibrate from their mean positive.
(G) Compare to cold water, ice cream appears cooler to the teeth because it has more "latent heat of vaporization" than ice cold water. Explanation: Since, ice cream has more latent heat so it will absorb more heat from teeth.
(H) The particles of water are held together by forces of attraction. It is the reason that the diver is able to cut through water in a swimming pool.
« Give reasons for the following observation: The smell of hot sizzling food reaches you several metres away, but to get smell from cold food, you have to go close.
(I) An earthen pot (matka) has many small pores. Water seeps out through them and evaporates from the surface of the pot. The energy needed for evaporation is taken from the water kept in the earthen pot. As a result, water kept in earthen pot becomes cool.
(J) (a) water at room temperature is liquid because at this temperature (i)it has fixed volume and (ii)it can flow. (B) An iron almirah is solid at room temperature because at this temperature (i) it has definite shape along with fixed volume and (ii) It can not flow like water and hence does not possess fluidity.
- At room temperature (anywhere from zero degree centigrade to 100 degrees centigrade), water is found in a liquid state. This is because of the tiny, weak hydrogen bonds which, in their billions, hold water molecules together for small fractions of a second. Water molecules are constantly on the move.
2. as almirah is a solid, so it has a definite shape and volume. so it is solid at room temperature. 2) the melting point of iron is very high (1538°) while the room temperature is 28°. as melting point of iron is very high as compared to room temperature, it is solid at room temperature.
(K) 1.Kerosene in a plate evaporates more rapidly than that poured in a bowl, because it evaporates quickly, being exposed over a larger surface. The latent heat required for evaporation is taken from water itself which therefore cools below the room temperature.