Week – 5 Lesson 2 Learning Objectives: Show an understanding of the term thermal capacity. Describe an experiment to measure the specific heat capacity of a substance Learn Keywords: Heat capacity and specific heat capacity. 1

Success criteria Define what specific heat capacity means. Establish the formula to calculate specific heat capacity. 2

Do now: Some materials are more difficult to heat up than others. You need 4200 J to warm 1kg of water but only 139 J to warm 1 kg of mercury by 1 °C Why? Hint: materials which need to gain lots of energy to warm up also release loads of energy when they cool down. 3

Some materials are more difficult to heat up than others. Why? They have a greater capacity for absorbing and storing heat (energy). Heat capacity. 4

Hypothesis Time: Specific heat capacity What three factors do you need to consider when calculating the amount of heat (energy) needed to raise the temperature of 1 Kg of gold? Write on your books, work in pairs. 5

The amount of heat needed to raise the temperature of a substance material depend on: 1- Mass of the material: the greater the mass= more particles need to be speed up=more energy needed HOW DO WE CALL THIS ENERGY?. What do you think will need more heat (energy) to raise the temperature? 2Kg or 20Kg of gold? Why (use previous knowledge)? Extension: Why does it takes longer to boil a kettle full of water than one only half full? Answer in terms of particles and energy. 6

The amount of heat needed to raise the temperature of a substance material depend on: 2- Type of material: heat capacity; we know different materials absorb and store more heat than others. A substance with great heat capacity will need more or less heat (energy) than one with low heat capacity? Why (use previous knowledge and key words)? 7

The amount of heat needed to raise the temperature of a substance (material) depend on: 3- How much temperature is raised (change in temperature). What would need more heat (energy) to raise the temperature; 10Kg gold by 10 °C 1 Kg of gold by 1 °C ? Why (use previous knowledge and key words) ? 8

Hypothesis time: Specific heat capacity The amount of heat needed to raise the temperature of a substance (material). Depends on: 1- mass: more mass=more particles=more heat needed to move all particles. 2- Type of material: heat capacity= how much heat a material absorbs and store. Great capacity = they absorb a lot of energy (difficult to heat up) less capacity=they don’t absorb lots of energy (easy to heat up) 3- How much the temperature is raised…obviously!!! Extension: What does a high specific heat capacity mean? Use your own words, key words, please. 9

Calculating specific heat capacity How do we find how much heat (Energy) do we need to raise the temperature in a mass of 1 kg? E= m × c × θ E = m = C = Θ = What do the symbols represent? Extension: What would be the units? (trust me you know the answer) 10

Calculating specific heat capacity E= m × c × θ E= energy (J) m=mass (Kg) C= heat capacity (J/Kg °C) θ= temperature change (°C) Extension: Rearrange the formula to find specific heat capacity. DRAW A FORMULA TRIANGLE) Remember the Units.. Very, very important. energy specific heat capacity temperature change =massxx 11

Do now: 1. The SHC of water is 4200 J / kg o C How much does the internal energy increase if 0.5 kg of water is heated by 10 o C? 2. The SHC of aluminium is 880 J / kg o C How much does the internal energy increase if 1 kg of aluminium is heated by 10 o C? Extension: Water has a very high specific heat capacity (4200 J/kg°C). What does this mean? What would happen if water had a low specific heat capacity? 12

Answers 1.E = m x c x θ = 0.5 x 4200 x 10 = J 2. E = m x c x θ = 1 x 880 x 10 = 8800 J EXTENSION: Water takes a huge amount of energy to heat up, but take a long time to cool down too. Life would have not evolved, water absorbs the right amount of energy for life to develop. 13

Some materials are more difficult to heat up than others. Why? They have a greater capacity for absorbing and storing heat (energy). 14

Worksheet 1 Work on the worksheet 1 Do now: 15

Worksheet 2 Do now: 1. The SHC of water is 4200 J / kg o C How much does the internal energy increase if 0.5 kg of water is heated by 10 o C? 2. The SHC of aluminium is 880 J / kg o C How much does the internal energy increase if 1 kg of aluminium is heated by 10 o C? Extension: What would happen if water had a low specific heat capacity? 16

Answers 1.E = m x c x θ = 0.5 x 4200 x 10 = J 2. E = m x c x θ = 1 x 880 x 10 = 8800 J EXTENSION: Life would have not evolved, water absorbs the right amount of energy for life to develop. 17

Home work Practice questions Exam practice: The specific heat capacity of water is 4200 J/Kg °C. How much energy is needed to raise the temperature of 3Kg of water by 4 °C? 18

1. If I want to raise the temperature of 250 Kg of gold by 25 °C. How much energy would I need taking in consideration the heat capacity for gold is 129 J/Kg °C? 19

2. How much thermal energy is needed to raise the temperature of 6Kg of gasoline by 15 °C if the specific heat capacity of gasoline is 2220 J/Kg °C? 20

3. How much thermal energy is required to raise the temperature of 3kg of aluminium from 15 °C to 25 °C? (The specific heat capacity of aluminium is 900 J/Kg °C). 21

4. Aluminium has a specific heat capacity of 900 J/Kg °C. A block of 10Kg of aluminium cools from 100 °C to 50 °C. How much thermal energy does give out? 22