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Twenty Questions. Review for Test. Twenty Questions. 1. What are the four signs of a chemical reaction?. Change in color Produces a gas Forms a solid Produces energy. 2. A chemical reaction that gives off energy. Exothermic Reaction.
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Twenty Questions Review for Test
1. What are the four signs of a chemical reaction? • Change in color • Produces a gas • Forms a solid • Produces energy
2. A chemical reaction that gives off energy. • Exothermic Reaction
3. A shorthand notation that uses chemical symbols and numbers to represent a substance. • Chemical Formula
4. The 2 in the formula Ag₂S is called a ____________ • Subscript
5. What kind of reaction forms a new substance that has different properties than the starting substances? • A Chemical Reaction
6. How many total atoms does 4NaOCl have? • 12 total atoms
7. A solid formed in a solution as a result of a chemical reaction. • precipitate
8. The number written below and to the right of a chemical symbol in a formula. • A subscript
9. The starting materials in a chemical reaction. Located on the left side of the yield sign. • Reactants
10. The substances formed from a reaction. They are located on the right side of the yield sign. • product
11. A ___ uses chemical formulas as a shorthand description of a chemical reaction. • Chemical equation
12. The law that states mass is neither created nor destroyed in ordinary chemical and physical changes. • The law of conservation of mass. .
13. The law that states that energy can be neither created nor destroyed. • The law of conservation of energy.
14. The smallest amount of energy needed for substances to react. • Activation energy
15. A substance that speeds up a reaction without being permanently changed. • catalyst
16. A substance that slows down or stops a chemical reaction. • An inhibitor
17. A slice of apple turning brown is an example of a ________ change. • chemical
18. Breaking a stick in half is an example of a _____change. • physical
19. Balance the following equation: HCl + Na₂S ⃗H₂S + NaCl • 2HCl + Na₂S ⃗H₂S + 2NaCl