Combustion

7. The process where a liquid forms solid crystals, often by cooling or evaporating.
9. Fuels made from living organisms or their waste, like ethanol or biodiesel.
11. Harmful substances released into the environment, often as a by-product of combustion.
12. The environment around a reaction, including air, temperature, and materials nearby.
13. A compound made of hydrogen and carbon atoms, such as methane or petrol.
16. Machines that convert energy from combustion into mechanical motion.
17. The visible, glowing part of a fire caused by combustion.
19. Reacting with great energy or intensity, like a fire burning strongly.

1. A historical, now-discredited theory that substances released a material called "phlogiston" during burning.
2. A reaction that releases heat to the surroundings.
3. A reaction where a substance combines with oxygen, often releasing energy.
4. Fuels formed from the remains of ancient plants and animals, such as coal, oil, and gas.
5. A rapid and violent release of energy caused by combustion or other reactions.
6. A chemical reaction where a substance reacts with oxygen, releasing energy as heat and light.
8. Energy released from reactions involving atomic nuclei, such as in nuclear power plants.
10. A small flash of light or heat that can start combustion.
14. A compound formed when an element reacts with oxygen, such as carbon dioxide.
15. Fuels made from resources that can be replenished, like biofuels.
18. Fuels from finite resources, like coal or oil, which cannot be replaced once used.