Thermal Energy
Thermal Energy Measurement related to the quantity of molecules. the total of all the kinetic and potential energy of all the particles in a substance.
Thermal Energy Relationships As temperature increases, so does thermal energy (because the kinetic energy of the particles increased). Even if the temperature doesn’t change, the thermal energy in a more massive substance is higher (because it is a total measure of energy).
HEAT Cup gets cooler while hand gets warmer The flow of thermal energy from one object to another. Heat always flows from warmer to cooler objects. Heat is the result of molecules vibrating quickly. Heat is moving energy. Ice gets warmer while hand gets cooler
Heat and Particle Movement Relationship
TEMPERATURE Measure of kinetic energy of molecules Thermometer Fahrenheit Celsius Kelvin
Conduction: heat energy travels through solids by vibrating particles
The transfer of heat from one object to another by direct contact between objects or particles.
Your feet transfer (conduct) heat to a cold tile floor. Examples: Your feet transfer (conduct) heat to a cold tile floor. A spoon placed in hot soup becomes warmer as the spoon conducts heat away from the hot soup.
Convection: heat energy travels through gases and liquids because the particles move around (current)
Heat transferred by the movement of molecules within a substance. Movement occurs from warmer areas to cooler areas.
Convection Current The movement of a substance that is caused by differences in temperature and density. Examples: wind boiling water Nature wants everything to balance!
Consider this - when you look at the road in the summertime on a hot day, you may notice that the air above the road looks “blurry” – this is convection taking place as the hot air directly over the road absorbs the heat from the road and rises. Although the explanation can be quite complex, convection can help explain why mirages are seen in the desert.
:heat energy travels through waves without a medium – solid, liquid, gas
Heat transferred through space. All objects emit (give out) and absorb (take in) thermal radiation (heat energy). However materials radiate and absorb heat better than others. EXAMPLE: the sun’s rays causing a sunburn.
Thermal radiation is also known as infrared radiation.
Which color/surface absorbs thermal radiation the best? Black Shiny gray Matt grey White
Which hand feels hot first? Why?
Which color of teapot should you put your tea in? Why?
Radiation Conduction Convection *Transferred in rays or waves *Energy from the Sun warms the Earth *Transfer of heat that happens when molecules bump into each other *Objects must be touching *Transfer of heat by the flow of material *In warm air, the molecules move apart, so it is less dense and rises *In cooler air, the molecules move closer together, so it is more dense and sinks Example: Example Review
Which radiates heat better; black material or silver material Which radiates heat better; black material or silver material? Which absorbs heat better; Explain choice?
Review http://open2.net/sciencetechnologynature/worldaroundus/kitchenchaos_embedded.html
Why is it colder in the night than in the day? The sun is the greatest heat source in the world. As the sun comes up, it warms the world. As the sun goes down, the heat is taken away and it cools off.
What will happen to this cold snowman throughout the day as the sun warms it up? The warmth of the sun will cause the snowman to melt.
What would happen to the temperature of the boiling water in this kettle if ice cubes were added? The coolness of the ice cubes would change the temperature of the water from hot to lukewarm.
How is the change in temperature of the snowman and the boiling water related? The temperature of both the snowman and the boiling water changed to a temperature that was not really cold or really hot, but rather somewhere in the middle.
Conductors Conductors are materials that transfer heat easily. Conductors hold heat in faster than others
The molecules in a conductor are close together The molecules in a conductor are close together. This allows the heat to move to all parts of the pot and the stew in the pot. Examples: metals like copper and gold
Insulators An insulator is a material that does not transfer heat easily. The molecules in an insulator are far apart. This helps prevent heat from flowing in or out. They do not let heat in quickly.
Insulators and conductors allow us to somewhat control the flow of heat or the change in temperature of objects.