Focus On Physical Science: California Grade 8

Chapter 8: Chemical Reactions

Standards Review

1.
Which of these is a chemical change? 5.a
A)boiling
B)rusting
C)dissolving
D)melting
2.
A _______ is a molecule composed of two or more different atoms. 3.b
A)reactant
B)element
C)compound
D)product
3.
When baking soda combines with vinegar, _______ occurs. 5.a
A)burning
B)a physical change
C)boiling
D)a chemical reaction
4.
Which is true when a chemical reaction occurs? 5.a
A)Materials mix evenly with each other.
B)A material changes from a solid to a liquid.
C)New substances are produced.
D)The change can be easily reversed.
5.
Which happens to the number of atoms in a chemical reaction? 5.b
A)The number could increase or decrease, depending on the chemical reaction.
B)The number of atoms doesn't change.
C)The number of atoms increases
D)The number of atoms decreases.
6.
Which is a substance that is formed by chemical reaction? 5.a
A)element
B)compound
C)product
D)reactant
7.
During a chemical reaction the _______ doesn't change. 5.b
A)formula units
B)number of molecules
C)number of compounds
D)number of atoms of each element
8.
Oxygen gas is a(n) _______. 3.b
A)diatomic molecule
B)formula unit
C)compound
D)ionic compound
9.
Which is a balanced chemical equation? 5.b
A)2K + Br2 ® 2KBr
B)K + Br2 ® 2KBr
C)2K + 2Br2 ® 2KBr
D)K + Br2 ® KBr
10.
How many hydrogen atoms are in the compound CH2(OH)2? 5.b
A)six
B)two
C)three
D)four
11.
Which best describes the law of conservation of mass? 5.b
A)The total mass decreases if the reaction is endothermic.
B)The total mass increases if the reaction is exothermic.
C)A chemical reaction produces mass.
D)The mass of the reactants always equals the mass of the products.
12.
Which is true for an exothermic chemical reaction? 5.c
A)Energy is given off when bonds are broken.
B)The products have more energy stored in their bonds than the reactants have stored in their bonds.
C)The reactants have more energy stored in their bonds than the products have stored in their bonds.
D)Energy is absorbed when bonds are formed.
13.
According to the law of conservation of energy, in a chemical reaction, _______. 5.c
A)energy is neither created or destroyed
B)energy must be added to the reactants
C)energy stored in the reactants is converted into light
D)energy stored in the reactants is converted into thermal energy
14.
A chemical reaction that absorbs energy _______. 5.c
A)violates the law of conservation of mass
B)is an exothermic reaction
C)violates the law of conservation of energy
D)is an endothermic reaction
15.
When chemical bonds are formed, ________. 5.c
A)energy is released
B)energy is absorbed
C)the reaction is endothermic
D)the reaction is exothermic
Grade 8
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