Heat and Heat Technology Section 1 Temperature

Essential Questions Describe how temperature relates to kinetic energy. Compare temperatures on different temperature scales. Give examples of thermal expansion.

What is Temperature? Temperature is a measure of kinetic energy. Kinetic energy is the energy of motion. All moving objects have kinetic energy. Kinetic energy of an object depends on the object’s mass and speed.

Temperature and Kinetic Energy All matter is made of atoms or molecules that are always moving. The faster the particles move, the more kinetic energy they have. The more kinetic energy an object has, the higher the temperature of the object.

The gas particles on the right have more kinetic energy than those on the left. So, the gas on the right is at a higher temperature.

Average Kinetic Energy of Particles Motion in matter is random, so each particle has a different amount of kinetic energy. An object’s temperature is the average kinetic energy of the particles in the object.

Measuring Temperature Thermometers can measure temperature because of thermal expansion. Thermal expansion means that when a substance’s temperature increases, its particles move faster and spread out – creating more volume (expansion).

Temperature Scales The Celsius scale is the most widely used temperature scale. The Fahrenheit scale is the one we use in the US. The Kelvin scale is the official SI temperature scale. The lowest temperature on the Kelvin scale is 0 K, which is called absolute zero.

Temperature Conversions Temperature is represented by different numbers on the three temperature scales.

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More About Thermal Expansion Expansion Joints on Highways Hot weather can make a bridge expand as the bridge expands, it is in danger of breaking. Expansion joints keep segments of the bridge apart so that they have room to expand without the bridge breaking.

Bimetallic Strips in Thermostats are made of two metals stacked in thin strips. The metals expand at different rates, a strip coils and uncoils in response to changes in temperature, as shown below.