Bell work The temperature of boiling water is 100° on the Celsius scale and 212° on the Fahrenheit scale. Look at each of the following temperatures and decide whether you think that it is hot or cold: 60°F 60°C 37°F 37°C0°C 100°F and70°F

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

Temperature

 Measure of kinetic energy of molecules  Thermometer  Fahrenheit  Celsius  Kelvin

Kinetic energy  Kinetic energy is the energy of motion. All moving objects have kinetic energy.  The amount of kinetic energy that an object has depends on the object’s mass and speed.

Kinetic energy  The faster the particles of an object are moving the hotter they are.  When you use a thermometer you are measuring the average kinetic energy of all the particles in an object.

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

Average Kinetic Energy of Particles The motion of particles in matter is random, so individual particles have different amounts of kinetic energy. When you measure an object’s temperature, you are measuring the average kinetic energy of the particles in the object.

Measuring Temperature

 The lowest temperature on the Kelvin scale is 0 K, which is called absolute zero.  Absolute zero (about −459°F) is the temperature at which all molecular motion stops. It is not possible to actually reach absolute zero.

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

Celsius to Fahrenheit °C → °F Fahrenheit to Celsius °F → °C Celsius to Kelvin °C → K K = °C Kelvin to Celsius K → °C °C = K − 273

Measuring Temperature  As a substance's temperature increases, its particles move faster and spread out.  So, there is more space between them, and the substance expands.  Thermal expansion is the increase in volume of a substance because of an increase in temperature.

Thermal Expansion-uses How a Thermostat Works

Thermal Expansion-uses  We know that hot air rises. Hot air balloons work using this principal.  When a gas is heated its particles have more kinetic energy.  They move around more quickly, so there is more space between them.  As it expands, it becomes less dense than the air outside the balloon.

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