Thermal Properies Of Materials

Question 1

What is thermal equilibrium?

Answer 1

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.

Question 2

What is the Kelvin Scale?

Answer 2

A thermodynamic scale that does not depend on a material’s properties.

Question 3

What are the fixed points of the Kelvin Scale?

Answer 3

• Triple point of pure water
• Absolute zero

Question 4

Define the triple point.

Answer 4

The temperature and pressure at which the three phases coexist in thermal equilibrium.

Question 5

Convert 0°C to Kelvin.

Answer 5

273 K

Question 6

Describe the particle arrangement in solids.

Answer 6

Fixed lattice with no space between particles.

Question 7

What are the intermolecular forces like in solids?

Answer 7

Strong

Question 8

How do particles move in solids?

Answer 8

Vibrate about fixed positions.

Question 9

What is the particle energy in solids?

Answer 9

Low

Question 10

Describe the particle arrangement in liquids.

Answer 10

Random with some space between particles.

Question 11

What are the intermolecular forces like in liquids?

Answer 11

Weak

Question 12

How do particles move in liquids?

Answer 12

Move past each other.

Question 13

What is the particle energy in liquids?

Answer 13

Medium

Question 14

Describe the particle arrangement in gases.

Answer 14

Random with large space between particles.

Question 15

What are the intermolecular forces like in gases?

Answer 15

Negligible

Question 16

How do particles move in gases?

Answer 16

Move at different speeds in any direction.

Question 17

What is the particle energy in gases?

Answer 17

High

Question 18

What is Brownian motion?

Answer 18

The phenomenon when small particles suspended in a liquid or gas are observed to move around in constant random motion.

Question 19

What does Brownian motion provide evidence for?

Answer 19

The existence of molecules in a gas or liquid.

Question 20

Define internal energy.

Answer 20

The sum of kinetic and potential energies of molecules within a substance.

Question 21

What factors determine internal energy?

Answer 21

-Temperature
-Random motion of molecules
-Phase of matter
-Intermolecular forces

Question 22

How can internal energy be increased?

Answer 22

-Doing work
-Adding heat

Question 23

What is absolute zero?

Answer 23

The lowest possible temperature (0 K or -273°C) where molecules have no kinetic energy.

Question 24

Which state has the highest level of internal energy?

Answer 24

Gas

Question 25

Which state has the least internal energy?

Answer 25

Solid

Question 26

What happens during phase changes?

Answer 26

Kinetic energy stops increasing, and energy goes into breaking intermolecular bonds.

Question 27

What is specific heat capacity?

Answer 27

The thermal energy required to raise the temperature of a substance by 1°C per unit mass.

Question 28

What does low specific heat capacity indicate?

Answer 28

Heats and cools quickly.

Question 29

What does high specific heat capacity indicate?

Answer 29

Heats and cools slowly.

Question 30

What is specific latent heat?

Answer 30

The thermal energy required to change the state of a substance without any temperature change.

Question 31

What is the specific latent heat of fusion?

Answer 31

Energy required for melting.

Question 32

What is the specific latent heat of vaporization?

Answer 32

Energy required for boiling.

Question 33

How can internal energy be decreased?

Answer 33

-Losing heat -Changing phase

Question 34

Relationship between internal energy and temperature?

Answer 34

Thermal energy is directly proportional to temperature.

Question 35

Specific Heat Capacity Units

Answer 35

Jkg^-1K^-1

Question 36

Specific Heat Capacity Equation

Answer 36

E=mcΔθ

Question 37

Specific Latent Heat Equation

Answer 37

E=mL

Question 38

Specific Latent Heat Units

Answer 38

Jkg^-1

Question 39

Explain the practical to determine the specific heat capacity in a solid.

Answer 39

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.

Question 40

Explain the practical to determine the specific heat capacity in a liquid.

Answer 40

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.

Question 41

Analysis of specific heat capacity results.

Answer 41

- Calculate change in temperature. - Calculate the heat supplied using: Energy = current x voltage x mass Then use E=mcΔθ to find c.

Question 42

Evaluation of specific heat capacity practical.

Answer 42

- 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.

Question 43

Explain the practical to determine specific Latent Heat of Fusion.

Answer 43

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.

Question 44

Analysis of Specific Lantent Heat of Fusion practical.

Answer 44

- 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.

Question 45

Evaluation of Specific Latent Heat of Fusion Practical.

Answer 45

- 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.

Question 46

Explain the practical to determine specific Latent Heat of Vaporisation.

Answer 46

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.

Question 47

Analysis of the practical to determine specific Latent Heat of Vaporisation.

Answer 47

- Calculate energy supplied using: Energy = Current x Voltage x time. - Calculate SLH using: E=mL

Question 48

Evaluation of the practical to determine specific Latent Heat of Vaporisation.

Answer 48

- 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.