(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.

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.

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.

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.

Atmospheric gases can be liquefied if a high pressure is applied at some low temperature.

(i) \(25°C\) +273=298K
(ii) \(373°C\) +273=646K

Salt and sugar consist of small particles which have fixed shape.

When a crystal of pottasium permaganate is dropped in a glass tumbler containing water, then the colour of pottasium permanganate spreads throughout the water in the glass.This shows that the particles of matter are continuosly moving.

Melting point is the temperature at which solid remains in equilibrium with its liquid form.Ice melts at 273 K.At 273 K heat given to ice disappears as latent heat of fusion and therefore temperature does not rise till all the ice is melted.

A wooden chair is a solid because
(a) it is rigid.
(b) it has definite shape.

(a) Take a tiny crystal of dry blue ink.Ink is a matter.Dissolve it in 100mL water.The colour of water becomes blue.Dilute 1mL of this blue water with 99mL clear water.Water again becomes blue though intensity of colour decreases.Repeat 2-3 times.The solution obtained remains coloured through intensity of colour decreases gradually.This shows that one tiny crystal of link contains millions of ink particles which are very very small
(b) Add 2g salt in a cylinder containing water marked at 100mL.Salt dissolves and disappears but the volume of water remains at 100 mL mark.This means salt particles get into spaces between water particles.Water is a matter and particles of water have spaces between them.
(c) Put a drop of perfume in one corner of the room.Stand at the other end.Stil you will get smell of perfume.This is because of matter, i.e., perfume are moving with air
(d) In the above case particles of perfume and that of air intermix with each other.This intermixing of particles of two different types of matter on their own is called diffusion.
(e) Open a water tap.Try to break the stream of water with your fingers,You will find that the stream of water does not cut.This is because particles of matter attract each other with a force that keeps the particles together.