What is Convection? Convection is one of the major modes of heat transfer. Convection takes place in liquids & gasses but not in solids.

Let�s do an activity to understand this process.

1. Take a round bottom flask and fill it two-thirds with water.
2. Place it on a tripod and put some crystals of potassium permanganate at the bottom of the flask using a drinking straw.
3. Now, light the flame & heat the water.

What do you observe? When water is heated, the water near the flame gets hot and its color becomes purple. Purple-colored hot water rises up while the cold water from the sides moves down towards the source of heat. This process continues till the whole water gets heated. This is how the heat is transferred in the process of �Convection�.

You might be thinking that how does the heat is transferred in the air? Air also follows the same process.

Let�s do another activity to understand the �Convection process in the air�

1. Take a cylindrical glass trough. Place a lit candle in it. Take circular cardboard with two identical holes. Cover the trough with cardboard in such a way that one of the holes lies above the lit candle. Use adhesive tape to fix it. Now, place a lit incense stick on the other hole of the cardboard. You will observe that the smoke from the incense stick is going into the trough and coming out from the hole above the candle.
2. It happens because the hot air above the lit candle rises up and to occupy its place the cool air from outside enters into the trough through the second hole to take its place.
3. The smoke that is emitted by the incense stick is pushed through the second hole when the cool air comes down.

This process repeats again and again that is, warm air rises up and comes out from the first hole & the cool air moves down through the second hole. Convection currents also assist in the ventilation of mines.

Sea Breeze and Land Breeze

Don�t you think that why people go to sea beaches for a lovely holiday? Actually, the people living in the coastal areas experience an interesting phenomenon. i.e. the phenomenon of Convection. During day time, land near the sea gets heated faster than water. Why does it happen? Because solids get heated faster than liquids and gases as well.

As a result of this, the air above land becomes hotter and rises up. This creates a low-pressure area or a gap. To occupy this gap the cooler air from the sea reaches towards the land. The cool air that flows from the sea towards the land is called Sea Breeze.

The warm air from the land moves towards the sea to complete the cycle. To receive the cool sea breeze, the windows of the houses in coastal areas are made to face the sea. At night, the reverse process takes place. The water cools down slowly as compared to land. It means the air above the sea at this point is comparatively warmer than the air above the land. As the warm air from the sea rises up, the cool air from the land moves towards the sea. This is called the land breeze.

Now you understand that why the atmosphere in coastal regions always remains pleasant, because, these regions are blessed with natural convection.

Read More: What is Conduction? Transfer Of Heat By Conduction | Conductors