Download 8th Grade Ch. 7 Chemical Reactions Study guide

8th Grade Ch. 7 Chemical Reactions Study guide
True/False
Indicate whether the statement is true or false.
____
1. According to the law of conservation of mass, three atoms of calcium can react to produce six atoms of
calcium.
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2. Chemical equations are balanced by changing the subscripts of the molecules.
____
3. Energy is needed to break bonds in chemical reactions.
____
4. A chemical reaction in which more energy is absorbed than is released is endothermic.
____
5. All chemical reactions occur at the same rate.
____
6. Activation energy is the minimum amount of energy needed for a chemical reaction to begin.
____
7. Exothermic reactions do not require any activation energy.
____
8. When a chemical equation contains the same number of atoms on both sides, the equation is balanced.
____
9. Lowering the temperature slows down most chemical reactions.
____ 10. The rate of a reaction is the speed at which products form or reactants disappear.
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____ 11. Evidence that a chemical change has occurred includes a ____.
A. change in state B. change in size C. change in shape D. change in color
____ 12. You can slow down the rate of a reaction by ____.
A. increasing concentration B. increasing temperature
inhibitor
____ 13. In an exothermic reaction, heat is ____.
A. absorbed B. conserved C. released
C. decreasing particle size
D. adding an
D. destroyed
____ 14. Activation energy is necessary for a chemical reaction to occur because ____.
A. breaking bonds requires energy B. some reactions happen at cold temperatures
endothermic D. forming bonds requires energy
____ 15. Presence of a catalyst ____.
A. stops a reaction B. raises the activation energy needed
activation energy needed
C. all reactions are
C. slows down a reaction
D. reduces the
____ 16. To check whether an equation is balanced, ____.
A. add the number of reactants to the number of products B. make sure the masses of the reactants and
products are the same C. count the number of each type of atom on each side D. check to see if the
reaction is endothermic or exothermic
____ 17. Energy is usually only shown with the products in an equation for ____.
A. an endothermic reaction B. a synthesis reaction C. an exothermic reaction
____ 18. The only balanced equation shown is ____.
D. activation energy
A. H2 + O2 H2 O
B. AgNO3 + NaIAgI + NaNO3 C. Ag + H2SAg2S + H2 D. Na + Cl2NaCl
____ 19. The presence of a(n) ____ speeds up a reaction.
A. reactant B. catalyst C. product D. inhibitor
____ 20. Heat is absorbed during ____ reactions.
A. activation B. endothermic C. enzyme
D. exothermic
____ 21. Substances formed during chemical reactions are ____.
A. catalysts B. oxides C. reactants D. products
____ 22. A ____ is a process in which new substances are formed.
A. chemical reaction B. catalyst C. reactant D. subscript
____ 23. The melting of ice is an example of a(n) ____.
A. chemical change B. endothermic reaction
C. exothermic reaction
____ 24. For a chemical reaction to begin, ____ is needed.
A. combustion B. a catalyst C. activation energy
D. physical change
D. a spark
____ 25. Chemical reactions usually speed up at ____ temperatures.
A. Celsius B. lower C. higher D. absolute
____ 26. Catalysts ____ the activation energy needed to start a chemical reaction.
A. inhibit B. increase C. reduce D. balance
____ 27. To check that an equation is balanced, count the number of ____ on each side of the equation.
A. ions B. molecules C. atoms of each type D. types of elements
____ 28. The ____ is a measure of how fast a reaction proceeds.
A. rate of reaction B. catalyst effect C. activation energy
D. concentration
____ 29. The size of the reactant particles can affect the ____ of a reaction.
A. temperature B. product C. concentration D. rate
____ 30. Which of the following changes is chemical rather than physical?
A. Water is boiled. B. Aluminum foil is crumpled. C. Glass is shattered.
D. Wood is burned.
____ 31. Each substance written to the right of the arrow in a chemical equation is a ____.
A. reactant B. product C. precipitate D. catalyst
____ 32. According to the law of conservation of mass, how does the mass of the products in a chemical reaction
compare to the mass of the reactants?
A. There is no relationship. B. The mass of products is sometimes greater. C. The mass of reactants is
greater. D. The masses are always equal.
____ 33. Which of the following changes gives NO evidence that a chemical reaction has taken place?
A. A cube of solid forms a puddle of liquid. B. A certain liquid is added to a solid, and bubbles of gas form.
C. Two liquids are mixed, and a precipitate forms. D. Heating a blue solid turns the solid white.
____ 34. When the following chemical reaction is balanced, what number is placed before NH3?
N2 + 3H2  NH3
A. 1 B. 2 C. 3 D. 6
____ 35. Which one of the following factors would not speed up a chemical reaction?
A. increasing the concentration of a reactant B. adding a catalyst C. raising the temperature
the reactant particles larger
____ 36. Which of the following materials will burn the fastest in open air?
D. making
A. a log, two feet in diameter
from a two-foot diameter log
B. two logs, each one foot in diameter C. a pile of small splinters made
D. Both logs and the splinters will burn at the same rate.
____ 37. A substance that speeds up chemical reactions in the human body is ____.
A. an inhibitor B. an enzyme C. polar D. a prohibitor
Matching
Tell whether each equation is either balanced or unbalanced.
A. balanced
B. unbalanced
____
____
____
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38.
39.
40.
41.
MgCO3 + 2HClMgCl2 + H2CO3
2H2 + O2H2O
CaCl22Ca +Cl2
Zn + 2HClZnCl2 + H2
Problem
An iron nail (Fe) is placed into a solution of copper(II) sulfate (CuSO4). After some time, the blue color of the
copper(II) sulfate disappears and some copper-colored solid (Cu) is found on the surface of the nail. The
solution now contains iron(II) sulfate (FeSO4), and the container feels warmer than before the reaction.
42. List the reactants.
43. List the products.
44. Write a balanced chemical equation for this reaction.
45. Does this reaction absorb or release energy? How do you know?
46. What do the color changes indicate?
Determine whether the following chemical equations are balanced or unbalanced.
47. H2 + O2  H2O
48. P4+ 5O2  P4O10
49. Fe2O3 + CO  2Fe + CO2
50. 2HCl + CaCO3  CaCl2 + H2O + CO