Question

Which of the following is an example of heat transfer by conduction?

the upstairs of a house being warmer than the downstairs
burning your finger on a hot match
the sun warming your skin
being warmed by a fire on a cold night
giving a medal

Answer 1

I think b

Answer 2

There are a few ways to transfer heat: convection, conduction, and radiation.

Convection is when heat (or energy in general) is transferred by movement. The hot stuff (water, air, whatever) moves to another location.

Conduction is when heat is transferred through matter. The hot thing (like a stove burner) touches a pan and the pan beings to get hot also. (Heat energy is being transferred from the atoms in the stove to the atoms in the pan.)

Radiation is when heat energy moves directly through space, like sunlight does.

Let's consider each of the four:

1) the upstairs of a house being warmer than the downstairs
How does upstairs get warm? Hot air rises. In that case, the hot air itself is moving, os that's convection.

2) the sun warming your skin
The hot stuff on the sun isn't moving directly to you (that would be bad!), so it isn't convection. You're not touching it (also bad), so it's not conduction. It's radiation -- the energy moving through space from the sun to you on the earth.

3) being warmed by a fire on a cold night
I think this is partly radiation - energy moving from the fire to you - and partly convection - hot air flowing in your direction. If you're being heated by conduction in this case, you are actually on fire, so that's not it.

4) burning your finger on a hot match
This comes from touching the match. The energy from the match moves into you -- so that's conduction!

Answer 3

Conduction is a form of heat transfer by directly touching the heat source, so the correct answer is burning your finger on a hot match. the sun warming your skin is heat transfer via radiation since the radiation from the light waves of the sun are on your skin. Upstairs will be warmer than downstairs because hot air masses are less dense than cooler air masses, causing the warmer air masses to move up; this is convection.