1.3 Heat Energy & Temperature

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It is important to understand the difference between heat and temperature.

Heat, as we saw in Section 1-1, is the amount of kinetic energy in a sample of matter. It flows in the direction from the warmer object to the colder object.

The SI unit of energy, including heat energy, is the joule (J), and is formally defined as the amount of energy produced when a force of one newton acts over a distance of one meter. How much energy is one joule?

One joule is the amount of energy used by a 100 W light bulb in 0.01 s.
One joule is approximately equal to the amount of energy you expend when you bring a cheeseburger to your mouth.
An ordinary paper match, burned completely, releases a little over 1,000 J.

[You may also be familiar with another unit of heat energy, the calorie (cal). To read a bit more about the calorie, follow this link.]

Temperature is a measure of the average kinetic energy of a sample of matter. It is theintensity of heat energy.

Temperature is measured in degrees celsius (°C) or in kelvin (K). Kelvin is the SI temperature scale. You may already know that at the temperature known as absolute zero (0 K), particle motion is as slow as it can possibly be. That's as cold as you can theoretically get!

Research

What is the coldest temperature scientists have been able to achieve in the lab?

To convert between celsius and kelvin:

\(\mathrm{^{\circ}C = K -273}\) \(\mathrm{K = ^{ \circ}C + 273}\)

For example:

Convert 25°C into Kelvin.

\(\mathrm{K = 25^{ \circ}C + 273 = 298K}\)

(the degree symbol is not used with K)

Convert 500 K into degrees celsius

\(\mathrm{^{ \circ}C = 500K -273 = 227^{ \circ}C}\)