Heat Transfer Notes
How does a cooler keep drinks cold on a hot day?
The cooler has insulating material - something that is a poor conductor and does not allow thermal energy to transfer well.
How can a solar heating system heat your water on a day when there's no sun?
A solar heating system includes containers that store the heat collected on a sunny day. This heat is stored in such materials as hot water or stones.
Why is the attic of a house always warmer than the basement?
Air is heated by convection. Warm air is always less dense and lighter. Heavier, denser, cooler air sinks and pushes warmer air upward.
When two cars sit in the sun all day, the one with the black roof gets hotter than the one with the white, shiny roof. Why?
Black absorbs radiant energy from the sun. White or shiny objects reflect the sun's energy.
How does the heat from the sun, thousands of miles away, reach your body?
By radiation
Why does clean snow melt more slowly than dirty snow
Dirt in the snow is dark in color and absorbs radiant energy from the sun. This causes the snow to melt. Clean snow reflects more of the sun's heat energy away.
How does a cold can of soda become warm on a hot day?
Heat energy outside the can warms the metal can (a good conductor) by conduction. Warmth from the surface of the can then transfers through the liquid by convection.
How does heat get from the stove burner into your soup?
Heat from the burner warms the pan by conduction. The liquid soup is warmed by convection currents.
Why is your house warm on a cold day, even if you haven't turned on the heat?
Houses are usually insulated with materials that do not transfer thermal energy well. Heat usually flows from warmest spots to cooler spots. The insulating materials hold the heat in the house.
Why is the metal spoon in your cup of hot chocolate hot?
Metal is a good conductor of heat. The heat energy moves from the hot liquid through the spoon by conduction.
How does a microwave oven get your food hot?
Microwaves carry radiant energy to the food. This causes the molecules in the food to vibrate rapidly and produce thermal energy (heat).
Why doesn't a plastic spoon in hot chocolate feel hot?
Plastic is a poor conductor of heat energy.
When you turn on a heater, how does the warmth get to you?
The warmth travels through the air by convection.
Why are you warmer with several layers of clothes than with just one heavy jacket?
When you wear layers, air is trapped between layers. Your body heat warms these many pockets of air, and they add extra insulation to keep in your body heat.
Why do some cooking pots have wooden handles?
Wood is a poor conductor of heat - this is a protection to keep hands from burning.