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Give another FIVE examples, each with a short explanation.
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4.2 Convection:
ASSIGNMENT 6: TO ILLUSTRATE HEAT-EXCHANGE DUE TO CONVECTION
Requirements: Pyrex beaker
Glass tube
Burner
Cold water
Potassium permanganate crystals
What do you observe?
1. What is the colour of the crystal?
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2. What happens to the coloured water around the crystal when the heating begins?
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3. What happens to the coloured water near the surface?
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THE APPLICATION OF CONVECTION IN EVERYDAY LIFE
When the windows are opened on top and below the hot air leaves the room through the top windows and fresh cool air enters through the lower windows.
In fridges, the freezer pipes are situated at the top. The cold air descends and cools the whole fridge.
When a kettle with water is placed on a warm stove plate the liquid is heated by means of convection.
Motorcar engines are cooled with water that circulates around each cylinder. By means of convection assisted by the water pump the hot water circulates to the top tank of the radiator. In the thin pipes of the radiator heat is radiated out to the air. The water in the bottom tank is therefore colder than the water in the top tank.
During the day the land becomes hotter than the sea. The air over the land also becomes warmer and rises. Cooler air coming from the sea takes the place of the warm air. This is how a sea breeze occurs.
Give another two examples of convection. Explain what is happening.
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