Thermal Physics Flashcards
Temperature simple definition
Temp is the measure of the average kinetic energy of ta substances particles
Equation for Power -
P = IV
Equation for Energy
E = PT
How can we calculate energy from Current and Voltage?
E = IVT
What is conduction?
Conduction is a passing vibration from a high temperature.
Why might metals conduct more than wood?
Because of free moving electrons which increases conduction
Why does heat conduct faster in metals?
Because metals are better conductors than, eg. wood, meaning the rate of conduction will be increased (rate of energy transfer)
What effect does surface area have on conduction?
Larger surface area to volume ratio means it will conduct heat quicker making it a better conductor.
Vice versa, a smaller surface area to volume ratio means the rate of conduction will be lower.
How does a larger mass affect insulation?
More mass means a smaller surface area to volume ratio, therefore the heat is insulated more and the rate of conduction is lower.
How does the difference in room temperature and water temperature affect rate of conduction?
The higher the difference between room and water temperature, the higher the rate of conduction.
What is important to remember about change in temperature and difference in temperature?
Rate of Change of Temperature is proportional to the Difference in Temperature
What is thermal conductivity?
Thermal conductivity is the energy transferred per second through an insulating material
What is the relation between thermal conductivity and energy transfer?
The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material.
What does the thickness of an insulating material do?
The thicker the insulating layer, the lower the rate of energy transfer through it.
What are the 3 types of energy transfer?
- Conduction
- Convection
- Radiation
What are some examples of insulation in buildings?
- Loft Insulation
- Cavity Wall Insulation
- Double-Glazed Windows
- Aluminium Foil behind Radiators
- External Walls with Thicker Bricks
What are physical changes?
Physical Changes are change which are REVERSIBLE and include changing state
What are chemical changes?
Chemical changes are when a chemical reaction occurs, and involve the formation of new chemical elements or compounds
What can happen if one heats something up?
If one transfers thermal energy to something, it can either INCREASE IN TEMPERATURE or CHANGE STATE
Note
Really need to understand the Temp / Time graph in book
What is the specific heat capacity?
The energy required to increase the temperature of 1kg of a substance by 1°C
What is the specific latent heat?
The energy required to change the state of 1kg of a substance WITHOUT A CHANGE IN TEMPERATURE.
What are the two different phases of specific latent heat?
Fusion - From solid to liquid
Vaporisation - From liquid to gas
What is the formula for the Specific Heat Capacity?
Energy / Mass Change x Change in Temperature
ΔE / mΔθ
What is the unit for specific heat capacity?
J / Kg°C
What is the formula for Specific Latent Heat?
Energy / Mass
E / M
What are the implications of water having a high specific heat capacity?
Water can absorb a large amount of heat, meaning there will not be a significant rise in temperature despite the large amount of energy.
Water can MINIMISE CHANGES in TEMPERATURE.
Eg. Specific Heat Capacity of water is 5X greater than that of the land, (sand), so the land cools down far faster than the sea once the sun goes down
What is the internal energy of an object?
The sum of the KINETIC and POTENTIAL energies of all its particles.
What is the kinetic energy when measuring an energy transfer?
It is to do with the speed of the particles, eg. Increase in temperature means particles move faster.
What is the Potential Energy when measuring an energy transfer?
Potential energy is to do with the separation of the particles, eg. Changing state when a liquid vaporises to a gas means the particles will expand which increases its potential energy.
What is important to remember when considering potential and kinetic energy during an energy transfer?
Potential energy can stay the same while kinetic energy can stay the same, vice versa. This can be seen in the Temp / Time Graph!!! (When the line levels out there is an increase in potential energy (when changing state) and when the gradient of the line increases the kinetic energy is increasing.)
What is the specific heat capacity of Water?
4,200 J/Kg°C
Required Practicals -
- Measuring Specific Heat Capacity
- Thermal Insulation
How to answer a 6 marker -
TALK ABOUT EQUATION!!!
Eg.
- Equation
- Measurements
- Current with Ammeter
- Voltage with Voltmeter
- Calculation (ΔE = IVT)
- Measuring Mass with balance
- Talk about initial temp and final temp (with thermometer)
- Calculate Δθ
ETC.
How are the following measured?
P.D. Ɪ T θ M
P.D. = Voltage (voltmeter)
Ɪ = Current (ammeter)
T = Time (stopwatch)
θ = Temperature (thermometer)
M = Mass (balance / scales)
