2. Twenty Questions Review for Test

3. Twenty Questions 12345 678910 1112131415 1617181920

4. 1. What are the four signs of a chemical reaction? Change in color Produces a gas Forms a solid Produces energy

5. 2. A chemical reaction that gives off energy. Exothermic Reaction

6. 3. A shorthand notation that uses chemical symbols and numbers to represent a substance. Chemical Formula

7. 4. The 2 in the formula Ag ₂S is called a ____________ Subscript

8. 5. What kind of reaction forms a new substance that has different properties than the starting substances? A Chemical Reaction

9. 6. How many total atoms does 4NaOCl have? 12 total atoms

10. 7. A solid formed in a solution as a result of a chemical reaction. precipitate

11. 8. The number written below and to the right of a chemical symbol in a formula. A subscript

12. 9. The starting materials in a chemical reaction. Located on the left side of the yield sign. Reactants

13. 10. The substances formed from a reaction. They are located on the right side of the yield sign. product

14. 11. A ___ uses chemical formulas as a shorthand description of a chemical reaction. Chemical equation

15. 12. The law that states mass is neither created nor destroyed in ordinary chemical and physical changes. The law of conservation of mass..

16. 13. The law that states that energy can be neither created nor destroyed. The law of conservation of energy.

17. 14. The smallest amount of energy needed for substances to react. Activation energy

18. 15. A substance that speeds up a reaction without being permanently changed. catalyst

19. 16. A substance that slows down or stops a chemical reaction. An inhibitor

20. 17. A slice of apple turning brown is an example of a ________ change. chemical

21. 18. Breaking a stick in half is an example of a _____change. physical

22. 19. Balance the following equation: HCl + Na ₂S ⃗H₂S + NaCl 2HCl + Na ₂S ⃗H₂S + 2NaCl

23. 20. What is the chemical formula for Carbon dioxide? CO ₂