Twenty Questions

1. Twenty Questions Review for Test

2. Twenty Questions

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

4. 2. A chemical reaction that gives off energy. • Exothermic Reaction

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

6. 4. The 2 in the formula Ag₂S is called a ____________ • Subscript

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

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

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

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

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

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

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

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

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

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

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

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

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

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

21. 19. Balance the following equation: HCl + Na₂S ⃗H₂S + NaCl • 2HCl + Na₂S ⃗H₂S + 2NaCl

22. 20. What is the chemical formula for Carbon dioxide? • CO₂