Science Answer the questions.[Che-3M]

1. Dry it under the fan: Under the fan when the speed of wind increases, the particles of water vapour from the shirt move away with the wind, decreasing the amount of water vapour in the surroundings. It increases the rate of evaporation of water and the washed wet shirt dries more quickly.
   
2. Use hanger for exposing its larger surface to air: When shirt is spread, it has large surface area. This makes the evaporation of water faster. Due to this, shirt dries up more quickly.
   
3. Dry it in Sun: On sunny day, temperature of atmosphere is more, therefore, the rate of evaporation increases. It is because, on increasing temperature, more particles of water get enough kinetic energy to go into the vapour state. This increases the rate of evaporation.
   
4. Use iron: By the use of iron, temperature increases and water converts into vapour state (steam) very quickly. Hence, rate of evaporation increases and shirt dries very quickly.
   

1. The substances X, Y and Z are water, ice and steam, respectively.
2. The process of conversion of X into Y is known as freezing.
3. At 0°C X is converted to Y.
4. Boiling or vaporisation is the name of the process of conversion of X to Z.
5. At 100°C X gets converted to Z.

1. The physical states are:

• A-liquid.
• B-gas.
• C-solid.
• D-plasma.
• E-Bose-Einstein condensate (BEC).

2. Ammonium chloride; and the name of the process is sublimation.
3. Carbon dioxide.
4. Water.
5. Plasma is the state of matter that allows the sun and the other stars to glow.

1. Characteristics of a solid:

• Solids have a fixed shape and fixed volume.
• Solids do not flow.

2. Characteristics of a liquid:

• Liquids have a fixed volume but no fixed shape, they take the shape of the vessel in which they are placed.
• They generally flow easily.

3. Characteristics of a gas:

• Gases can be compressed easily.
• Gases fill their container completely.

• Take 2-3 crystals of potassium permanganate and dissolve them in 100ml of water.
• Take out approximately 10ml of this solution and put it into 90ml of clear water.
• Take out 10ml of this solution and put it into another 90ml of clear water.
• Keep diluting the solution like 5 to 8 times.
• Is the water still coloured?

This experiment shows that just a few crystals of potassium can colour a large volume of water. So we conclude that there must be millions of tiny particles.

1. Melting point is directly related to inter molecular forces of attraction i.e. higher is the inter molecular forces of attraction, higher is the melting point.

Melting point is the temperature at which solid phase is converted into liquid phase. Thus to break the strong molecular forces present in solid, energy has to be supplied in the form of heat which helps to break the forces and molecules gain kinetic energy which overcome the inter molecular forces and thus liquid phase is achieved.

2. Latent heat of vaporization is the amount of heat required to convert 1 gram of liquid into its vapor state without change in its temperature. The latent heat of vaporization of water is 40.67 kJ/mol.

Latent heat of fusion is the amount of heat required to convert 1 gram of solid into its liquid state without change in its temperature. The latent heat of fusion of water is 6.01 kJ/mol.

In fusion or melting, the molecules just need enough energy to slide around each other, while for vaporization, they need enough energy to completely escape the system. Thus the enthalpy of vaporization is always going to be higher than the enthalpy of fusion.

1. LPG (liquefied petroleum gas) is a fuel which is made up of petroleum gas. On compressing this petroleum gas it forms liquid.
2. Oxygen cylinders in the hospitals have compressed gas filled in it.
3. CNG (compressed natural gas) is a natural gas, methane, which is compressed and used as a fuel in vehicles and at home.

1. By compressing the gas at temperatures less than its critical temperature.
2. By making the gas do some kind of work against an external force, causing the gas to lose energy and change to the liquid state.
3. By using the Joule-Thomson effect.

1. Osmosis: a, c, d and e.
   
2. Diffusion: b, f and g.
   

1. Evaporation produces cooling.This is based on the fact that when a liquid evaporates, it takes (or draws) the latent heat of vaporisation from ‘another matter’ which it touches. This ‘another matter’ looses heat and gets cooled. Therefore, evaporation causes cooling.
2. If humidity is high, then air is already saturated with water vapours, i.e., it has a lot of water vapours. Therefore, it will not take more water vapours easily. Hence, rate of evaporation decreases.
3. Sponge has minute holes in which air is trapped. The material is also not so rigid. On pressing this, air is expelled out, that is why it can be compressed but it is solid as it has a definite shape and volume and does not change its shape unless compressed.

1. Swelling up of a raisin on keeping in water.

3. Earthworm dying on coming in contact with common salt.

4. Shrinking of grapes kept in thick sugar syrup.

5. Preserving pickles in salt.

2. Spreading of virus on sneezing.

6. Spreading of smell of cake being baked throughout the house.

7. Aquatic animals using oxygen dissolved in water during respiration.