Thermal Properies Of Materials Flashcards
What is thermal equilibrium?
Energy is transferred from a region of high temperature to a region of low temperature
Occurs when objects at different temperatures transfer heat until they reach the same temperature.
Objects must be in physical contact, be the same temperature and have no net energy transfer between them to reach thermal equilibrium.
What is the Kelvin Scale?
A thermodynamic scale that does not depend on a material’s properties.
What are the fixed points of the Kelvin Scale?
- Triple point of pure water
- Absolute zero
Define the triple point.
The temperature and pressure at which the three phases coexist in thermal equilibrium.
Convert 0°C to Kelvin.
273 K
Describe the particle arrangement in solids.
Fixed lattice with no space between particles.
What are the intermolecular forces like in solids?
Strong
How do particles move in solids?
Vibrate about fixed positions.
What is the particle energy in solids?
Low
Describe the particle arrangement in liquids.
Random with some space between particles.
What are the intermolecular forces like in liquids?
Weak
How do particles move in liquids?
Move past each other.
What is the particle energy in liquids?
Medium
Describe the particle arrangement in gases.
Random with large space between particles.
What are the intermolecular forces like in gases?
Negligible
How do particles move in gases?
Move at different speeds in any direction.
What is the particle energy in gases?
High
What is Brownian motion?
The phenomenon when small particles suspended in a liquid or gas are observed to move around in constant random motion.
What does Brownian motion provide evidence for?
The existence of molecules in a gas or liquid.
Define internal energy.
The sum of kinetic and potential energies of molecules within a substance.
What factors determine internal energy?
-Temperature
-Random motion of molecules
-Phase of matter
-Intermolecular forces
How can internal energy be increased?
-Doing work
-Adding heat
What is absolute zero?
The lowest possible temperature (0 K or -273°C) where molecules have no kinetic energy.
Which state has the highest level of internal energy?
Gas
Which state has the least internal energy?
Solid
What happens during phase changes?
Kinetic energy stops increasing, and energy goes into breaking intermolecular bonds.
What is specific heat capacity?
The thermal energy required to raise the temperature of a substance by 1°C per unit mass.
What does low specific heat capacity indicate?
Heats and cools quickly.
What does high specific heat capacity indicate?
Heats and cools slowly.
What is specific latent heat?
The thermal energy required to change the state of a substance without any temperature change.
What is the specific latent heat of fusion?
Energy required for melting.
What is the specific latent heat of vaporization?
Energy required for boiling.
How can internal energy be decreased?
-Losing heat
-Changing phase
Relationship between internal energy and temperature?
Thermal energy is directly proportional to temperature.
Specific Heat Capacity Units
Jkg^-1K^-1
Specific Heat Capacity Equation
E=mcΔθ
Specific Latent Heat Equation
E=mL
Specific Latent Heat Units
Jkg^-1
Explain the practical to determine the specific heat capacity in a solid.
1- Set up a circuit with an ammeter and voltmeter parallel to 1kg of a substance with an immersion heater and thermometer.
2- Measure initial temperature of substance.
3- Turn on power supply and stop watch.
4- Take initial readings of voltage and current.
5- After 5 mins turn off power supply.
6- Monitor thermometer and record highest temperature reached.
Explain the practical to determine the specific heat capacity in a liquid.
1- Set up a circuit with an ammeter and voltmeter parallel to a beaker of liquid with an immersion heater and thermometer.
2- Measure initial mass of liquid using a digital balance.
3- Measure initial temperature of substance.
4- Turn on power supply and stop watch.
5- Take initial readings of voltage and current.
6- After 600 seconds turn off power supply.
6- Monitor thermometer and record highest temperature reached.
Analysis of specific heat capacity results.
- Calculate change in temperature.
- Calculate the heat supplied using:
Energy = current x voltage x mass
Then use E=mcΔθ to find c.
Evaluation of specific heat capacity practical.
- Not all heat supplied will go to the substance, some is lost to surroundings.
Therefore, energy supplied value is too high and the SHC value calculated is larger than the actual. - There may be fluctuations in the power supply.
Combat this by taking several periodic measurements of voltage and current and use an average in the equations.
Explain the practical to determine specific Latent Heat of Fusion.
1- Set up 2 beakers on zero’ed scales, with clamps holding funnels containing 100g of crushed ice above each with filter paper. One funnel has an immersion heater in alongside the ice that’s connected to a circuit with an ammeter and voltmeter.
2- Turn on heater and stopwatch.
3- Record initial voltage and current.
4- turn off power supply after 10 mins.
5- Record mass of water in beakers.
Analysis of Specific Lantent Heat of Fusion practical.
- Calculate energy supplied with:
Energy = current x voltage x time - Find the difference in mass between the 2 beakers.
- Use E=mL where the mass is the difference and find L.
Evaluation of Specific Latent Heat of Fusion Practical.
- Errors may be introduced due to instruments precision.
-Water may be absorbed by filter paper, reducing the mass calculated and giving a higher SLH value.
Explain the practical to determine specific Latent Heat of Vaporisation.
1- Set up an outer flask, containing an inner flask full of after and an immersion heater connected to a circuit. The outer flask is placed on top of a condenser with a collecting flask beneath.
2- Start power and stopwatch.
3- Record initial voltage and current.
4- Turn off power of heater after 10 minutes.
5- Record mass of liquid collected in collecting flask.
Analysis of the practical to determine specific Latent Heat of Vaporisation.
- Calculate energy supplied using:
Energy = Current x Voltage x time. - Calculate SLH using:
E=mL
Evaluation of the practical to determine specific Latent Heat of Vaporisation.
- Errors may be introduced due to the instruments precision.
-Not all Vapor reaches the beaker meaning mass recorded is lower than the actual mass.
Therefore calculates SLH is too high.
