Answers Chemical Reactions magnesium and oxygen in MgO. Mg - Bridgeway

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Chemical Reactions

Chapter Test A 1. C 2. C 3. A 4. B 5. A 6. C 7. A 8. B 9. C

10. B 11. solid 12. products 13. activation energy 14. bias 15. replacement 16. F, Chemical 17. F, remains the same 18. T 19. F, Objective 20. F, dependent on 21. T 22. A physical change. The substance

was still wax, but it changed to a liquid and then back to a solid. 23. Carbon, hydrogen, and oxygen. No matter is created or destroyed in a chemical reaction, and so the elements present in the products must have been present in the reactants. 24. Exothermic. Heat is released when the candle (wax) burns. 25. The bonds between oxygen atoms in O2 are broken. Bonds form between

magnesium and oxygen in MgO. Mg and O2 are elements, and MgO is a compound.

26. A) The reaction is exothermic because heat and light are given off. The energy of the products is less than the energy of the reactants. B) The reaction is endothermic. Energy is absorbed by the reaction, making the solution feel cooler. The energy of the products is greater than the energy of the reactants.

27. Synthesis. Two elements (hydrogen and oxygen) combine to form a compound (water).

28. The burning splint supplies the activation energy needed to start the reaction between hydrogen and oxygen.

29. Notify the teacher.

30. The principle of conservation of mass states that matter cannot be created or destroyed during a chemical reaction. Therefore, the number and kind of atoms going into a chemical reaction must exactly equal the number and kind of atoms coming out of the reaction. A balanced chemical equation must show that all the elements present in the reactants are present in equal amounts in the products.

31. A synthesis reaction produces a more complex substance from simpler substances. A decomposition reaction produces simpler substances from a more complex substance. These two reactions are opposite processes.

Chemical Reactions Chapter Tests

Answers Chemical Reactions

(continued) 32. A) Enzymes are catalysts. They speed

up chemical reactions by lowering the activation energy of reactions needed for life. Enzymes allow reactions that are necessary for life to occur at body temperature. B) Sawdust has a greater surface area than wood. Increased surface area of a reactant will increase the rate of a chemical reaction. In this case, more of the reactant (sawdust) will come in contact with oxygen, so a spark is enough to start an explosion.

Chemical Reactions Chapter Tests

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