- When an animal moves , chemical energy is converted to mechanical energy
- A human is a kind of animal
- So, when a human moves, chemical energy is converted to mechanical energy

- When a human moves, chemical energy is converted to mechanical energy
- When one kind of energy changes into another kind of energy , the total amount of energy is constant
- Mechanical energy is a kind of energy
- Chemical energy is a kind of energy
- Hence, when a human moves, the total amount of energy is constant

Therefore, when a human moves, the total amount of energy is constant
The human body produces motion by changing chemical energy into mechanical energy. Which of these best describes what happens to the energy?
- When an animal moves , chemical energy is converted to mechanical energy 
- When one kind of energy changes into another kind of energy , the total amount of energy is constant 
- Mechanical energy is a kind of energy 
- A human is a kind of animal 
- Chemical energy is a kind of energy