Section 1: Temperature and Thermal energy practice quiz
- You should be able to determine what temperature is warmer or warmest if given a F, C, and K temperature
- You should be able to convert one temperature into another C = (5/9) (F-32) or F = (9/5)(C) +32 or K = C +273
- Think of the demonstration with the blowtorch... I had one metal ball that slipped through a metal hole. When the ball was heated up, (the molecules moved faster and) it expanded thus causing it to not fit through the metal hole anymore.
1. Temperature
- temperature is related to the average kinetic energy of the molecules an object contains
- most materials expand when their temperatures increase
- on the Celsius scale, the freezing point of water is 0 degrees C and the boiling point is 100 degrees C
- On the Fahrenheit scale, the freezing point of water is 32 degrees F and the boiling point is 212 degrees F.
- the thermal energy of an object is the sum of the kinetic and potential energy of all the molecules in an object
Section 2: Heat practice quiz
- Think of the lab that measured heating up and cooling down... what did the graph show, what were the results of the lab. What did you learn about how fast water heats up or cools down?
1. Heat and Thermal Energy
- Heat is the transfer of thermal energy due to a temperature difference
- heat always moves from a higher temperature to a lower temperature
- Conduction is the transfer of thermal energy when substances are in direct contact
- Radiation is the transfer of thermal energy by electromagnetic waves
- Convection is the transfer of thermal energy by the movement of matter
Think of an example of each conduction, convection, and radiation.
3. Thermal conductors and specific heat
- A thermal conductor is a material in which heat moves easily - metal is an example of a conductor
- An insulator is a material that does not transfer heat. In your house, windows have 2 layers of glass that sandwich a layer of air... this reduces the movement of heat out of the house in winter (or heat moving into the house during the summer) - plastic or wooden handles are good examples of insulators used in cooking
- The specific heat of a substance is the amount of heat needed to raise the temperature of 1 kg of the substance by 1 degree C. Think about your experiences relating to some materials that heat-up faster than other materials.
1. Heat engines and Energy
- A heat engine is a device that converts thermal energy into mechanical energy
- Energy cannot be created or destroyed. It only can be transformed from one form to another.
- An internal combustion engine is a heat engine that burns fuel in a combustion chamber inside the engine.
- A refrigerator uses coolant to transfer thermal energy to outside of the refrigerator
- The coolant gas absorbs thermal energy from inside of the refrigerator - think about water evaporating off of your skin, spraying a can of hairspray, using a propane tank (to burn the gas and heat a garage)... all of these have a liquid that boils and it feels cold. This is the same as what happens in the pipes that are inside the refrigerator.
- Compressing the coolant makes it warmer than the air outside of the refrigerator (thus when the pipes are exposed to the air, heat is transferred from the warm pipes to the cold(er) outside air). Examples of compressing and heating-up could be the fire syringe video. A diesel engine does this... compressing the air so much that it heats up to the point that the diesel fuel burns without a spark-plug having to ignite it.
- A heat pump heats by absorbing thermal energy from the air outside, and transferring it inside a building.
