_{Up Learn – A Level physics (AQA) – THERMAL PHYSICS}

_{Up Learn – A Level physics (AQA) – THERMAL PHYSICS}

**Using Specific Latent Heat to Calculate Energy Required for a Change of State**

**Using Specific Latent Heat to Calculate Energy Required for a Change of State****How to work out an energy change using specific latent heat of fusion or specific latent heat of vaporization.**.

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### More videos on Thermal Physics:

^{Introduction (free trial)}

^{Latent Heat}

^{Specific Latent Heat}

^{Calculating Energy Required for a Change of State}

^{Changing Temperature and State – Worked Example}

## Thermal Physics

*(free trial)*

2. Thermal Equilibrium

*(free trial)*

3. Heating and Kinetic Energy

*(free trial)*

4. What is Temperature?

*(free trial)*

5. Defining Temperature

*(free trial)*

6. Temperature Scales

*(free trial)*

7. The Kelvin Scale

*(free trial)*

8. Degrees Celsius to Kelvin

*(free trial)*

*(free trial)*

2. States of Matter

*(free trial)*

3. Intermolecular Forces

*(free trial)*

4. Forces or Bonds? – Article

*(free trial)*

5. What is Internal Energy?

*(free trial)*

6. Thermal Energy and Internal Energy – Article

*(free trial)*

7. Change in Internal Energy – Energy Transfer by Heating (Part 1)

*(free trial)*

8. Change in Internal Energy – Energy Transfer by Heating (Part 2)

*(free trial)*

9. Change in Internal Energy – Energy Transfer by Work

*(free trial)*

10. Change in Internal Energy – Heating and Work

*(free trial)*

11. ΔU = Q + W – Article

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12. Constant Internal Energy

*(free trial)*

*(free trial)*

2. Factors Affecting Temperature Increase – Mass and Energy

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3. Factors Affecting Temperature Increase – Specific Heat Capacity

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4. Calculating Energy Required to Increase Temperature

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5. Objects in Thermal Equilibrium

*(free trial)*

6. Worked Example – Calculating Temperature at Thermal Equilibrium

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7. Assumption of Energy Transfer

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8. Calculating c Using Gravitational Potential Energy

*(free trial)*

9. Calculating c for a Solid using Electrical Energy

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10. Calculating c for a Liquid using Electrical Energy

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11. Calculating c Using Continuous Flow 1

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12. Calculating c Using Continuous Flow 2

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We’ve seen that the energy required to change 1 kilogram of material from the solid state to liquid state is known as the specific latent heat of fusion…

And the energy required to change 1 kilogram of material from the liquid state to gas state is known as the specific latent heat of vaporisation.

And these values depend on the material itself.

Now, if we want to change the state of more than 1 kilogram of material…

If we want to change the state of more than 1 kilogram of material, we need more energy…

And if we want to change the state of less than 1 kilogram of a substance, we need less energy.

Therefore, the amount of energy required for a change of state depends on two things:

The mass of the material

And the specific latent heat of fusion or vaporisation.

And we can combine these factors in this formula [Q = ml]

Where Q stands for the energy required to change the state of a substance without a change in temperature, in joules…

m stands for the mass of the substance, in kilograms

And l stands for the specific latent heat of fusion or vaporisation, in joules per kilogram.

For example, here we have 20 kilograms of ice…

And ice has this specific latent heat of fusion.

[20.0 kg and 3.34 x 10^{5} J kg^{-1}]

To work out how much energy is required to turn all the ice into liquid water, we substitute these values into this formula…[Q = ml] [20.0 x 3.34 x 10^{5} ]

And calculate to get this! [6.68 x 10^{6} J]

So now, what is the value for Q in this example?

To work out the value for Q, we substitute the variables into this formula…

Which calculates to give this!

Finally, you can find this formula in the data and formulae sheet!

To sum up, to calculate the energy required for a change of state, we use this formula [Q = ml]

Where…

Q is the energy required to change the state of a substance without a change in temperature, reported in joules

M is the mass of the substance, reported in kilograms

And l is the specific latent heat of fusion or vaporisation, reported in joules per kilogram