CHAPTER 1 MATTER IN OUR SURROUNDINGS
DATE 04.04.16
QUESTION : Why do we observe that the level of water does not change even after the dissolving of salt in it ?
ANSWER : We observe this because the particles of water have gap between them and the particles of the salt get into the space and so the level does not increases .
DATE 05.04.16
PROPERTIES OF PARTICLES
1 Particles are very small in size .
2 Particles of matter are continuously ,it means that they have kinetic energy .
3 The particles of matter have space between them .
DATE 06.04.16
QUESTIONS : Why solids have fixed shapes ?
ANSWER : Solids have a fixed shapes because their the molecules in solid are in fixed positions and are closed together so , they can not move from one part to another part of the solid .
DATE 07.04.16
QUESTION : GIVE REASON
1 Why table is hard ?
ANSWER : Table is hard because the force of attraction in these molecules is very high and which results in close packing of molecules and it is very dense .
2 Why diver is able to cut water ?
ANSWER : Diver is able to cut the water because it is less denser and the attraction force is low so it has distance between the molecules and so the diver is able to cut the water .
3 Why the smell of hot sizzling food reaches our nose ?
ANSWER : Smell of hot sizzling food reaches our nose because in the hot temperature
the molecules move faster which results in reaches our nose .
DATE 18.04,16
EXERCISE
ANSWER 1
1) 293 K
= 298 C
2)470 K
= 646 C
ANSWER 2
1) 25 C
= 20 C
2) 373 K
= 197 C
ANSWER 3
a) Naphthalene balls dissapear with time as the temperature rises , it gets sublimated in gas without leaving any solid .
b) The molecules of perfumes gets mixed in the air molecules which is the least dense matter , that is why we get the smell perfume sitting several meters away .
ANSWER 4
- Oxygen - Water - Sugar
ANSWER 5
a) Liquid State
b) Solid State
c)Gaseous State
ANSWER 6
a) Water at room temperature has a medium force of attraction so it is in liquid form .
b) At room temperature , the inter molecular force of solid is so high that its molecules get packed together tightly .
ANSWER 7
At 273 k or 0 * c the ice will give more cooling than water bscause it can absorb more heat than water due to its latend heat of fusion .
ANSWER 8
Steam will cause more serve burns.
Latent heat of fusion
The heat required to change 1 kg of solid into liquid completely is known as latent heat of fusion. It is absorbed by a body during a constant temperature process that is specified in some way.
Latent heat of vaporization
The heat required to change 1 kg of liquid into vaporous at atmospheric pressure is known as the latent heat of vaporization.
Evaporation
The process of conversion of liquid into vapors is known as evaporation.
DATE 18.04.16
Factors affecting the rate of evaporation
1. Temperature- The rate of evaporation is directly proportional to the rise in temperature . more the temperature more will be the evaporation.
2. Humidity- The rate of evaporation is inversely proportional to the humidity. It means that the more the humidity is the less is the rate of evaporation.
3. Wind speed- The rate of evaporation is directly proportional to the wind speed. It means that more is the wind speed more will be the rate of evaporation.
4. Surface area- The rate of evaporation increases when the surface area increases as when the surface area will be increase the evaporation will also be increased.
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