Question

which of the following is a real - world example demonstrating convection?
select all that apply
a the flow of hot air from a space heater in a room.
b the heating of a metal spoon when placed in a hot cup of coffee.
c the heating and cooling of air in a hot air balloon to make it float in the sky.
d the melting of polar ice caps due to climate change.

Explanation:

• Option a: The flow of hot air from a space heater in a room. Hot air (less dense) rises and cooler air (more dense) moves in to replace it. This is a classic example of convection as it involves the movement of a fluid (air) due to temperature - induced density differences.
• Option b: The heating of a metal spoon when placed in a hot cup of coffee is an example of conduction. Heat is transferred through direct contact between the molecules of the coffee and the spoon.
• Option c: In a hot - air balloon, when the air inside is heated, it becomes less dense and rises (convection current). When the air is cooled (by releasing heat), it becomes more dense and the balloon descends. So, the heating and cooling of air in a hot - air balloon to make it float in the sky is based on convection.
• Option d: The melting of polar ice caps due to climate change is mainly due to the absorption of heat (from increased greenhouse gases in the atmosphere) which causes a phase change (solid to liquid). It is not a direct example of convection.

Answer:

A. The flow of hot air from a space heater in a room, C. The heating and cooling of air in a hot air balloon to make it float in the sky.