Distillation

 Distillation  is a process of separating the components on the basis of their volatility. Higher volatile component will be in vapour phase while less volatile component will remain in liquid phase. 

At a temperature the liquid and vapour phase will achieve equilibrium. When the temperature changes the composition of liquid and gas phase changes. In distilation column the temperature increases from top to bottom, so do the composition of components. At low temperature higher volatile component composition will be more in vapour phase and at high temperature less volatile component will be more in liquid phase. As many trays are there in Distillation column, as no. of equilibrium stages will be.

Reboiler at the bottom of distillation column keeps the temperature high in distillation column while the condenser at top keeps the temperature low.

We can reduce electricity consumption of AC

 In summer the air is very hot and dry. The temperature  of  the  air can be reduced either by desert cooler or AC. Can we use the both? The desert cooler works on evaporative cooling and decreases the temperature very cost effectively, but it also increases the humidity which causes uncomfortable. The humidity will be decreased by AC. So, here Cooler does the cooling and AC does the humidity control. Therefore, by using the combination of desert cooler and AC the cooling gets faster and cost effectively.

Why salt is added to make ice cream

 Adding salt decreases the freezing point of ice. We know pure ice melts at 0°C and if we add salt to it it starts melting at a lower temperature, let's say at -6°C. That means ice start melting at a faster rate than pure ice. That is why it is used in melting snow at roads. But do you wonder how is it helpful in freezing ice cream?

The answer lies in the huge difference in latent heat of melting and specific heat. The latent heat of fusion of ice is approx. 334 KJ/Kg while the specific heat of ice is 2.09 KJ/Kg°C. Let's consider an example, if we have 1 kg of an ice at -10°C. It will absorb 20.9 KJ heat from surrounding and start melting at 0°C. But if we add salt 100 gm of salt to 1 Kg of ice it will approximately decrease the freezing point to -6°C. So it will absorb 8.36 KJ of heat and reaches to -6°C and then start absorbing 334 KJ heat to melt. This means the temperature will be -6°C for quite long time and it will help infreezing ice cream.