Question

Select the cross words from the brackets to complete each sentence
1. If pressure on the surface of water increases, its boiling point …………. and freezing point ……………. [increases/decreases]
2. A saturated solution can be converted to an unsaturated solution by …………… [increasing/decreasing] the amount of the solvent.
3. Dissolved air in water contains a ……………. [higher/lower] percentage of oxygen than ordinary air.
4. At low temperatures the solubility of a gas in water is ………….. [less/more] compared to that at ordinary temperatures.
5. Efflorescence occurs when the vapor pressure of the hydrated crystals is …………. [more/less] than the vapor pressure of the atmospheric humidity.

Answer 1

Hint: Pressure is represented by the letter P which is defined as the force applied perpendicular to the surface of an object per unit area over which that force is distributed. SI unit of pressure is Pascal represented by Pa.

Complete Solution :
 Liquids have a characteristic temperature at which they turn into solids. This temperature is known as freezing point and a temperature at which the vapor pressure is large enough that bubbles form inside the body of the liquid and this temperature is known as boiling point. If pressure on the surface of water increases, its boiling point increases and freezing point decreases.
- A saturated solution is that which is dissolved as much solute as it is capable of dissolving and all other solutions are known as unsaturated solutions. A saturated solution can be converted to an unsaturated solution by decreasing the amount of the solvent.
- Dissolved air in water contains a high percentage of oxygen as compared to ordinary air; this is due to the reason that solubility of oxygen gas in water is more than nitrogen and other gases present in the air. This is due to the small size of oxygen as compared to nitrogen due to which it easily gets trapped inside the vacant space between water molecules.
- At low temperatures the solubility of a gas in water is less compared to that at ordinary temperatures. As solubility is dependent on temperature higher the temperature high is the solubility and vice versa.
Efflorescent substances are solids that can undergo spontaneous loss of water from hydrated salts. They do not absorb the water and efflorescence occurs when the vapor pressure of the hydrated crystals is more than the vapor pressure of the atmospheric humidity.

Hence these are true.
1. If pressure on the surface of water increases, its boiling point increases and freezing point decreases.
2. A saturated solution can be converted to an unsaturated solution by decreasing the amount of the solvent.
3. Dissolved air in water contains a higher percentage of oxygen than ordinary air.
4. At low temperatures the solubility of a gas in water is less compared to that at ordinary temperatures.
5. Efflorescence occurs when the vapor pressure of the hydrated crystals is more than the vapor pressure of the atmospheric humidity.

Note: Solution is generally made up of two substances named as solute and solvent where solute refers with the substance which is present in lower concentration while solvent is that substance which is present in higher amounts.