Internal energy and energy transfers 2

Question 1

What is meant by the term latent heat?

Answer 1

the energy needed for a substance to change state is
called latent heat

Question 2

Explain what is meant by the specific latent heat of a substance and how it is related to the energy required for a substance to change state.

Answer 2

the specific latent heat of a substance is the amount of
energy required to change the state of one kilogram of the
substance with no change in temperature

Question 3

What does the specific latent heat of fusion relate to, and what does it measure in terms of energy and state change?

Answer 3

specific latent heat of fusion relates to the change of state
from solid to liquid

Question 4

What does the specific latent heat of vaporisation relate to, and what change of state does it describe?

Answer 4

specific latent heat of vaporisation relates to the change
of state from liquid to vapour

Question 5

distinguish between specific heat capacity and specific
latent heat

Answer 5

Specific Heat Capacity:

Definition: The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kilogram of the substance by 1°C (or 1 K), without changing its state.
Energy and Temperature: When energy is added to a substance, its temperature increases (if no state change occurs).
Unit: The unit of specific heat capacity is Joules per kilogram per degree Celsius (J/kg°C).
Specific Latent Heat:

Definition: The specific latent heat of a substance is the amount of energy required to change the state of 1 kilogram of the substance without changing its temperature.
Energy and State Change: When energy is added, it causes the substance to change state (e.g., from solid to liquid or liquid to gas) without changing the temperature.
Unit: The unit of specific latent heat is Joules per kilogram (J/kg).

Question 6

investigation to determine the specific heat capacity of one or more materials. The investigation
will involve linking the decrease of one energy store (or work done) to the increase in temperature and subsequent increase
in thermal energy stored

Answer 6

𝑐

Aim:
To determine the specific heat capacity of a material by measuring the energy required to raise the temperature of a known mass of the substance.

Apparatus:
Power supply (e.g., battery pack)
Thermometer
Insulated calorimeter or beaker
Electrical heater (e.g., immersion heater)
Stopwatch
Digital balance (to measure mass)
Voltmeter and ammeter (to measure the electrical energy supplied)
Wires and connectors
Insulating material (to reduce heat loss)
Method:
Measure the Mass of the Material:

Measure the mass of the material (e.g., water or metal) using a digital balance. Record the mass in kilograms (kg).
Set Up the Heater:

Place the material (e.g., water) in an insulated calorimeter or a beaker to reduce heat loss.
Submerge the electrical heater in the material, making sure it doesn’t touch the sides or bottom of the container.
Record Initial Temperature:

Insert a thermometer into the material to measure its initial temperature. Record the temperature before heating starts.
Start Heating:

Connect the electrical heater to a power supply. Switch on the heater and begin heating the material.
Use the ammeter and voltmeter to measure the current and voltage supplied to the heater. Record the current and voltage at regular intervals.
Measure Temperature Change:

Use the thermometer to measure the temperature of the material at regular intervals (e.g., every 30 seconds). Record the temperature as the material heats up.
Continue Heating:

Continue to heat the material for a set period (e.g., 5–10 minutes), or until you achieve a noticeable temperature change (e.g., 10°C to 20°C rise).
Stop Heating and Record Final Temperature:

After a sufficient time, stop heating the material and record the final temperature.
Calculate Energy Supplied:

Use the voltmeter and ammeter to determine the energy supplied to the heater over the heating time.
The energy supplied (in joules) can be calculated using the formula:
𝐸
=
𝑉
×
𝐼
×
𝑡
E=V×I×t
Where:

𝐸
E = Energy supplied (J)
𝑉
V = Voltage (V)
𝐼
I = Current (A)
𝑡
t = Time (s)
Calculate Specific Heat Capacity:

Using the formula:
𝐸
=
𝑚
×
𝑐
×
Δ
𝑇
E=m×c×ΔT
Where:

𝐸
E = Energy supplied (J)
𝑚
m = Mass of the substance (kg)
𝑐
c = Specific heat capacity (J/kg°C)
Δ
𝑇
ΔT = Change in temperature (°C)
Rearrange the formula to solve for the specific heat capacity (c):

𝐸
𝑚
×
Δ
𝑇
c=
m×ΔT
E
​

Repeat for Accuracy:

Repeat the experiment for multiple trials to ensure accuracy and reliability in your result.
Safety Considerations:
Ensure the electrical equipment is set up safely to avoid electric shock.
Use insulated gloves when handling the heater to prevent burns.
Ensure the calorimeter is insulated to reduce heat loss to the surroundings.