3. Thermal Physics Flashcards
What is the formula to calculate density, mass or volume?
Density = mass / volume
What are three states of matter?
Define each states fixed shape or volume
What force is between the molecules?
Solid:
- Fixed shape and fixed volume
- Molecules held in position by a force. Vibrate but does not move
Liquid:
- No fixed shape, but fixed volume
- Force between molecules not so strong so molecules can move around
Gas:
- No fixed shape or volume
- No force between molecules (ideally)
Define temperature
A scalar quantity and measures in Celsius or kelvin; measures of how hot or cold an object is and therefore, determines the direction of heat flow
Convert 0 Celsius to Kelvin
0 C = 273 K
10 C = 273 + 10 = 283 K
Define Thermal Capacity (C)
The thermal capacity of a body is the amount of heat needed to raise its temperature by 1 C. Unit J C^-1
C = Q / deltaT
Q = quantity of heat delaT = temperature
Define specific heat capacity (c)
The quantity of heat (Q) required to raise the temperature of a mass (m) of material by (deltaT) then the specific heat capacity (c) of that material is given by:
c = Q / m x deltaT
Describe the change of state
Ice > melting > liquid
Liquid > freezing > ice
Liquid > vaporization > gas
Gas > condensation > liquid
Solid molecules have KE since they are vibrating, when energy is added, liquid molecules are now free to move about but have the same KE as before
Apply three types of actions to increase the rate of evaporation
- Increase of surface area
- Blowing across the surface
- Raising the temp
Define Avogrados constant
A mole of any material contains 6.022 x 10^23 atoms or molecules
Define specific latent heat (L)
The specific latent heat of a material is the amount of heat required to change the state of 1kg of the material without change of temperature
Unit: Jkg-1
L = Q / m
Q = Amount of energy m = Mass
Distinguish between the difference of boiling and evaporation
Boiling = Throughout the liquid; always the same temperature
Evaporation = Only at the surface of the liquid; happen at all temperature
State assumptions of the kinetic model of an ideal gas
- The molecules are perfect elastic
- The molecules are spheres
- The molecules are identical
- There are no force between the molecules = the molecules move with constant velocity between collisions
- The molecules are very small, that is, their total volume is m smaller than the volume of the gas
What happens when the temperature of an gas increases?
If the temperature increases, then the speed of the particles will increase. Molecules in a hot gas have higher average KE
Define pressure
Pressure = Force / Area
• Volume of the area decrease = Increased pressure
