Thermal Energy and Heat Chapter 16 Thermal Energy and Heat
Bellwork – How would you describe temperature?
1. What are the scales of temperature? Fahrenheit Celsius Kelvin
2. What is heat? Heat is the energy transferred between objects that are at different temperatures. From higher temperature lower temperature.
3. What is Temperature? Measure of the average kinetic energy of the particles in an object. All matter is made of atoms or molecules that are always moving. The faster the particles are moving, the more kinetic energy they have. The more kinetic energy the particles of an object have, the higher the temperature of the object is.
4. Which particles have a higher temperature and why? Faster particles causes more kinetic energy, and therefore higher temperature.
When you measure an object’s temperature, you are measuring the average kinetic energy of the particles in the object. 5. Thermometers can measure temperature because of a property called thermal expansion. Thermal expansion is the increase in volume of a substance in response to an increase in temperature. As a substance’s temperature increases, its particles move faster and spread out.
6. Why are sidewalks cut up into different segments and not one continuous piece of concrete? Expansion joints or cuts keep segments of the sidewalk apart so that they have room to expand without the sidewalk breaking.
7. How can we convert between different scales of temperature? Fahrenheit to Celsius Celsius to Fahrenheit Celsius to Kelvin Kelvin to Celsius SI Unit for temperature is Kelvin. Other scales include Fahrenheit and Celsius.
STOP! Bill Nye will talk to you about Heat transfer.
8. Specific Heat Specific Heat is the amount of energy needed to change the temperature of 1 kg of a substance by 1°C. The higher the specific heat of something is, the more energy it takes to increase its temperature. Most metals have very low specific heats. On the other hand, the specific heat of water is very high.
9. Measuring Heat Unlike temperature, energy transferred between objects can not be measured directly. Instead it must be calculated with the following equation: E(Q) = mCT heat (J) specific heat (J/kg•°C) mass (kg) change in temperature (°C)
We are skipping this. m=0.2 kg Q = (0.2)(4184)(55) Q = mcΔT Q = 46024J 10. Calculate the heat transferred to a mass of 0.2 kg of water to change the temperature of the water from 25ºC to 80ºC. The specific heat of water is 4,184 J/(kg*ºC). We are skipping this. Given and Unknown Equation Substitution Solution m=0.2 kg Q = (0.2)(4184)(55) Q = mcΔT c=4184 J/kgC Q = 46024J ΔT=80⁰-25⁰ 55⁰C
We are skipping this. Example Calculations Given and Unknown Equation 11. How much heat was absorbed by 100 g of water if the temperature of the water went up 9ºC. The specific heat of water is 4.2 J(g*ºC). Given and Unknown Equation Substitution Solution
Example Calculations Continued We are skipping this. 11. If we assume the heat lost by the piece of metal is absorbed by the water. What is the specific heat of the metal if the temperature of the metal went down 65ºC and the mass of the metal was 55 grams. Given and Unknown Equation Substitution Solution
12. Calorimeters A calorimeter is a device that measures heat. When one object transfers thermal energy to another object, the energy lost by one object is gained by the other object.
13. Thermal Conduction is the transfer of thermal energy from one substance to another.
Heat Transfer Convection is the transfer of thermal energy by the movement of a liquid or a gas.
Heat Transfer 15. Radiation is the transfer of energy by electromagnetic (EM) waves. All objects radiate EM waves. Unlike conduction and convection, radiation can involve either a transfer of energy between particles of matter or an energy transfer across empty space.
16. First Law energy cannot be created or destroyed. 17 16. First Law energy cannot be created or destroyed. 17. Second law heat flows from hot to cold– in order to move the other way, work must be done. 18. Third Law a state of 0 temperature (0 kinetic energy) can only exist at absolute zero.