Science puzzle

3. A molecule with two or more hydrogen atoms bonded to a single carbon atom
5. The transfer of thermal energy through direct contact
7. A mixture that can be separated into its components through physical means
9. The study of living organisms
12. The force that keeps objects moving in a circular path
14. A neutral particle found in the nucleus of an atom
15. A substance that speeds up a chemical reaction without being permanently changed
17. The study of forces and their effects on motion
19. The process by which cells divide to create new cells
20. A process that breaks down food using oxygen
21. The study of electricity and magnetism

1. The process of living things obtaining nutrients for energy and growth
2. The process by which plants capture energy from sunlight
4. The force that opposes motion
6. The basic unit of heredity passed from parent to offspring
8. The transfer of thermal energy through waves or radiation
10. The study of matter and its properties
11. The force that pulls objects towards the Earth
13. A balanced system where the forces acting on an object cancel each other out
16. The smallest unit of a chemical element that can exist
18. Tiny building blocks of all matter