- A car engine started and converted gasoine into heat and sound energy
- Gasoline is a source of chemical energy
- Therefore, a car engine started and converted the chemical energy in gasoline into heat and sound energy

- A car engine started and converted the chemical energy in gasoline into heat and sound energy
- Sound is a kind of mechanical energy
- Therefore, a car engine usually converts chemical energy into mechanical energy and heat energy

- A car engine usually converts chemical energy into mechanical energy and heat energy
- When one kind of energy changes into another kind of energy , the total amount of energy is constant
- Hence, when the car engined started the total amound of energy is constant

Therefore, when the car engined started the total amound of energy is constant
Question
When a car engine is started, gasoline is mixed with air and burned. Heat, sound, and chemical products are released. As the engine operates, which of these remains constant?

Context
- A car engine started and converted gasoine into heat and sound energy 
- Sound is a kind of mechanical energy 
- Gasoline is a source of chemical energy 
- When one kind of energy changes into another kind of energy , the total amount of energy is constant