Heat & Heat Technology Chapter 13
Temperature Measure of the average kinetic energy of the particles in an object Same average kinetic energy = equal temperature
Thermal expansion Increase in volume of a substance because of an increase in temperature
Absolute zero The lowest temperature on the Kelvin scale 0 K (about °C ) Temperature where all molecular motion stops Not possible to reach it
Converting temperatures Celsius to Fahrenheit °F = (9/5 x °C) + 32 Fahrenheit to Celsius °C = 5/9 x (°F – 32) Celsius to Kelvin K = °C Kelvin to Celsius °C = K – 273 Freezing point of water 32° F 0° C 273 K
Heat The energy transferred between objects that are at different temperatures
Thermal energy The total kinetic energy of the particles that make up a substance Measured in joules (J)
Thermal conduction The transfer of thermal energy from one substance to another through a material or direct contact
Thermal conductors A material through which energy can be transferred as heat Example: metals Curling iron Cookie sheet Iron skillet Copper pipe Stove coil
Thermal insulators A material that reduces or prevents the transfer of heat Examples Flannel shirt Oven mitt Plastic spatula Fiberglass insulation Ceramic bowl
Convection Transfer of thermal energy by the circulation or movement of a liquid or a gas Convection causes the repeated rising and sinking of water during boiling Wind is a result of earth heating by sun
Radiation Transfer of energy by electromagnetic waves like in visible light or infrared waves
Specific heat Amount of energy needed to change the temperature of 1 kg of a substance by 1°C
States of matter The physical forms in which a substance can exist Particles move at different speeds The “state” of a substance depends on Particle speed (kinetic energy) Attraction between particles (potential energy) Pressure around particles
3 familiar states of matter Solid Liquid Gas
Change of state A change of a substance from one state of matter to another Physical change only Just affects physical properties but NOT the identity of the substance (i.e. water is still water whether it is a solid, liquid, or a gas)
Changes of state Freezing: liquid to solid Melting: solid to liquid Boiling: liquid to gas Condensing: gas to liquid
Insulation Material that reduces the transfer of thermal energy (i.e. less heat passes into or out of) Used in walls, ceilings, and floors Helps houses stay warm in the winter Helps houses stay cool in the summer
Heat engine Machine that uses heat to do work Fuel combines with oxygen (O 2 ) in a chemical change that releases thermal energy
Thermal pollution Excessive heating of a body of water caused by human activity Happens with large power plants that are near bodies of water Harms animals living in water