- TEMPERATURE:
Temperature is a measure of the average kinetic energy of molecular motion.
At a temperature of absolute zero, there is no molecular motion.
Temperature above absolute zero is measured in Kelvin units, but this impractical for most purposes.
Scientists usually measure temperature in degrees Celsius (also called centigrade).
The Celsius temperature is always equal to the absolute (Kelvin) temperature minus 273.
Two important numbers to remember: water freezes (or ice melts) at 0o C, and
water boils at 100o C.
Comparison of all Kelvin, Celsius, and Fahrenheit temperature scales is shown on page 13 of
this reference chart.
- HEAT:
Heat is a measure of the total kinetic energy of random molecular motion.
Since heat is a form of energy, it is measured in Joules.
Heat can also be measured in calories: a calorie is defined as the amount of heat energy
needed to raise the temperature of 1 gram of water by 1o C.
1 calorie = 4.18 Joules
NOTE: 1000 calories is called a kilocalorie or "large Calorie," equal to the amount of heat required
to raise the temperature of a kilogram of water by 1o C.
The "Calories" on food labels are really kilocalories.
- Specific Heat:
The Specific Heat of any substance is the amount of heat needed to raise its temperature by one degree Celsius (which is also equal to 1 Kelvin).
The specific heat of liquid water is 4.18 Joules per gram Kelvin, which is also written 4.18 J / g K or 4.18 J / g oC
Water resists temperature change because of its high specific heat. Most other substances have a much lower specific heat, so they
change temperature more easily. Iron, for example, has a specific heat of only 0.45 J / g K
For any substance:
Specific heat = _ (heat energy added) _
mass * temp.change
or--
Heat energy needed = (Specific heat) * mass * temp.change
NOTE: Heat energy is usually in Joules. Mass is usually in grams. Temp.change is in oC or K (values are the same)
For a list of several other specific heat values, see page 1 of
this reference chart.
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