1. Natural Sciences Grade 7
Term 3: Energy and Change
Potential and kinetic energy

2. Topic 2 Potential and Kinetic Energy
Potential energy
Natural Sciences - Grade 7

3. Natural Sciences - Grade 7
Potential energy
It is energy that:
has the capacity to do work.
is stored in a system.
A system:
- consists of an input, a process and an output.
is made up of two or more parts that work together.
needs energy to work.
Natural Sciences - Grade 7

4. Natural Sciences - Grade 7
Potential energy
All objects that are held above the ground have potential energy.
Potential energy is also stored in fuel, batteries and food.
Natural Sciences - Grade 7

5. Potential energy examples
A brick that lies on the ground does not have any potential energy.
Once the brick is picked up, it has the ability (potential) to fall down to the ground.
Natural Sciences - Grade 7

6. Potential energy examples
A stretched elastic band has high potential energy.
The energy used to stretch the elastic band, remains stored in the elastic band until you let it go.
Natural Sciences - Grade 7

7. Potential energy examples
Books on a table: Books that rest on a table has potential energy, since it is above the ground. The potential energy is only available when it drops on the floor.
Natural Sciences - Grade 7

8. Potential energy in food
Our energy to keep on living comes from the food that we eat.
Our bodies turn the potential energy in food into energy for living and growing.
Energy is measured in joules (j). [joules are small amounts of energy].
People use kilojoules (kJ) [1 kJ = J].
Natural Sciences - Grade 7

9. Potential energy in food
It is very important to check the kilojoules listed on food’s packaging.
Food labels have nutritional information that inform us how much energy the food contains per serving.
Adults need approximately kJ of energy per day from food.
The next slide has a table with food that children prefer to eat.
Natural Sciences - Grade 7

10. FOOD ANALYSIS – KILOJOULES
Standard serving kJ
100g kJ
Beef steak [no fat]
1 serving [168g]
1 179
702
Baked beans
1 serving [270g]
918
340
Fried chicken
1 serving [72g]
238
1 385
Egg
medium [15g] 71
594
Potato crisps
1 serving [50g]
1 045
2 090
Natural Sciences - Grade 7

11. FOOD ANALYSIS – KILOJOULES
Standard serving kJ
100g kJ
Pizza slice
Water (tap)
Soda soft drink
Peanut butter
Bread (white)
Apple
Carrot
1 serving [100g]
1 cup [237g]
1 can [355g]
2 tbsp. [32g]
1 serving [30g]
1 med. [138g]
1 small [50g]
910
630
788
334
301 86
180
2 462
1 049
218
173
Natural Sciences - Grade 7

12. Important information on food packages
Lean: described on meat, poultry, seafood and game meat.
Less than 10g fat, 4.5g or less saturated fat, and less than 95mg cholesterol per reference amount or per 100 grams.
Extra lean: described on meat, poultry, seafood and game meat.
Less than 5g fat, less than 2g saturated fat and less than 95mg cholesterol per reference amount or per 100 grams. .
Natural Sciences - Grade 7

13. Important information on food packages
Good Source: the reference amount of a product contains 10 to 19% of the Daily Value of a particular nutrient (i.e. fibre, protein / a vitamin / a mineral).
High: the reference amount of a product contains 20% or more of the Daily Value for a particular nutrient (i.e. fibre, protein / a vitamin / a mineral).
Natural Sciences - Grade 7