(i) 50+273=323K
(ii) Activity Take little amount of water in three containers which have different surface areas. Keep hem in sunlight for 2 h. Measure the volume of water left in all three containers.
Observation The amount of water left will be least in container having largest surface area among them.
Conclusion Greater the surface area, more will be the rate of evaporation.

Water exists as solid water (ice), liquid water (water) and gaseous water (steam).The melting point of ice is 0⁰C.It does not mean that water is not available as solid at 0⁰C.It only means that at this temperature ice starts melting and at 0⁰ C both ice and water are in equilibrium.Similarly the boiling point of water as 100⁰ C does not mean that at this temperature there is no liquid water present.At 100⁰C actually both water and steam are in equilibrium.At these temperatures with a little change in energy one can move to either of the stats.This energy is called latent heat.The word 'latent' is used to signify that this heat is taken up or given by the system but not shown by rise or fall in temperature.

Evaporation is useful in our life as follows:
1.We wear cotton in summer.During summer we perspire more.These particles gain energy from body surface and due to pores in cotton clothes are able to evaporate.This keeps the body cool.
2.Wet clothes dry up in sunlight
3.After a hot sunny day, we sprinkle water on the roof or open ground because latent heat of vaporisation of water helps  us to cool the surface

(a) Matter
(b) Matter occupies space and mass
(c) matter is available to us solid, liquid or gas.
(d) Smell and love cannot be considered as matter as these are only feelings.You cannot assign any be mass or volume to a love or smell
(e) Trivial things can be significant.It should not be ignored.

At \(0°C\) , when the ice melts, the temperature of the system does not change through the heat is continuously supplied.The given heat is used up in overcoming the force of intermolecular attraction.This results in the conversion of ice into water.As this heat energy is absorbed by ice without any rise in temperature of the system, this heat is considered as hidden in the system and is known as latent heat.

We know that particles of matter are constantly moving.In solids, the constituent particles are able to vibrate only due to high intermolecular forces of attraction.In liquids, the particles are able to move but the forces of attraction are strong enough to keep these stick together.Thus in solids and liquids, the particles stay together and form a surface.In gases, the intermolecular forces of attraction are very weak and hence the particles move without any restriction in random motion.These thus occupy any available space and move away if there is an open space.That is why gases do not have open surface.

Characteristics of particles matter are:
(i) Particles of matter have space between them
(ii) Particles of matter are continuously moving and thus possess kinetic energy.
(iii) Particles of matter can diffuse into one another.
(iv) Particles of matter attract each other.The force of attraction varies from one kind of matter to another.
(v) Particles of matter have mass.

Matter exists in three states:
(i) Solid: A solid has a definite volume but its shape is not definite, it will depend on the shape of the container in which it is contained,e.e., 5ml each of water, petrol, alcohol kept in different types of containers will have different shapes but the volume of each of these liquids remains the same, i.e., 5ml
(ii) Gas: A gas has neither a definite shape nor a definite volume,e.g., hydrogen, air, nitrogen taken in different containers have the shape and volume of the containing vessel.

(i) Liquid diffusing into solid.If we put a drop of ink on the centre of a clean blotting paper, we find the liquid spreads out by diffusing into the blotting paper which is a solid.
(ii) Solid diffusing into liquid.When we put a crystal of potassium permanganate in water, slowly the colour of potassium permanganate spreads throughout water.
(iii) Diffusion of a solid into a solid.Diffusion of solids into solids is very very slow.So diffusion of a solid into other solids is rare and very small.When we write on a blackboard with a chalk, we can easily clean it.But if it is left uncleaned for few days, it becomes difficult to clean the blackboard.This is because there is a slight diffusion of chalk particles.i.e., solid into the solid blackboard.

Take a beaker half filled with water.Mark the level of water.Now add some matter like sugarm, salt or dettol in it.It will be observed that the added matter disappears and there is hardly and change in level of water.This is because particles of one matter, i.e., salt, sugar or dettol get into the sapces between the particles of the other matter, i.e., water.Thus we can say that there is enough between particles of matter.