Temperature

• The measure of how hot or cold something is

• Specifically – how fast the particles are moving, average kinetic energy

• Matter is made of atoms that are always moving, or they have kinetic energy

• The more kinetic energy, the higher the temperature

• Measuring temperature measures the average kinetic energy of an object

• Temperature is measured with a thermometer• Thermal expansion – increase in the size of a

substance in response to an increase in temp (as temp increases, particles move faster, spreading out)

• Because of thermal expansion, all materials can expand and shrink when temperature changes

• Mercury and alcohol are used in thermometers because they increase in size (expand) by constant amounts, stay liquid at high and low temperatures

• Fahrenheit– Boiling pt 212°– Freezing pt 32°

• Celsius– Boiling pt 100°– Freezing pt 0°

• Kelvin– Boiling pt 373– Freezing pt 273

• Lowest temp on Kelvin scale is 0 or absolute zero (-459°F), the temperature at which all molecules stop moving

• Heat – the energy transferred between objects that are at different temperatures

• Thermal energy – kinetic energy of a substances atoms

• Thermal energy is transferred from areas warmer to areas that are cooler until both are equal

Conduction – the transfer of energy, as heat, through a material (touching)

Conductors and Insulators

• Materials that transfer heat are called thermal conductors

• Materials that do not transfer heat are called thermal insulators

• Examples:– Insulators: feathers, blankets, plastics– Conductors: metals

• Thermal conductivity is the rate at which a material conducts heat

Radiation – the transfer of energy as electromagnetic waves (sun)

• Radiant energy from the sun heats earth

• Examples:– Fire– Radiator– Electric Oven– Electric stove

Convection is the transfer of thermal energy by the circulation or movement of a liquid or

a gas

• Energy transfer can not be measured directly, instead it must be calculated

• Heat = joules (J)

• Specific heat = (J/Kg x ° C)

• Mass = Kg

• Temperature = ° C

• Formula to calculate heat: J = (J/Kg x ° C) x Kg x ° C

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