AnswersFL-2003350-Chemistry 1 Honors Sem 1 - FlexEvidence of Chemical Reactions

Evidence of Chemical Reactions Answers

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During an experiment, Mr. Lehman tells his students to be alert for signs that an endothermic reaction is happening. Which of the following scenarios would his students most likely observe?

A
A test tube becomes cool to the touch.
B
A liquid appears to glow.
C
A new odor comes from a beaker.
D
A solid forms from a mixture of solutions.
2
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Which statement about a chemical reaction is true?

A
It occurs only at low temperatures.
B
It occurs only at high temperatures.
C
It occurs whenever a physical change takes place.
D
It occurs whenever a chemical change takes place.
3

Which is the most important question for deciding if a chemical reaction has occurred?

A
Was there a change in the size?
B
Was any heat energy given off?
C
What is the density of the substance?
D
What is the texture of the substance?
4

Which statement describes a chemical reaction?

A
Atoms in the products are rearranged to form new substances.
B
Atoms in the reactants are rearranged to form new substances.
C
Atoms in the products change into new atoms to form new substances.
D
Atoms in the reactants change into new atoms to form new substances.
5

Two different liquids are mixed together. Which observation indicates that an exothermic chemical reaction has taken place?

A
an increase in volume
B
a decrease in volume
C
a rise in temperature
D
a drop in temperature
6

A solid is placed in a solution. Which observation most likely indicates that a chemical reaction has occurred?

A
The size of the solid has rapidly decreased.
B
The color of the solution has not changed.
C
The solid has bubbles forming on its surface.
D
The temperature of the solution stays the same.
7

The images show two unrelated events occurring at separate times. Which event is most likely an example of a chemical reaction?

Question illustration
A
Event 1 because there is a color change.
B
Event 1 because there is a release of heat and light.
C
Event 2 because the temperature is dropping in the liquid.
D
Event 2 because the blue color mixes throughout the liquid.
8

Which term best describes the role of hydrogen gas in the formation of a water molecule?

A
catalyst
B
inhibitor
C
product
D
reactant
9

When sodium metal is added to water, an orange flame is observed on the metal surface. Based on this observation, what can best be concluded?

A
A physical change occurs because the metal gets smaller.
B
A chemical reaction occurs because the liquid becomes cloudy.
C
A chemical reaction occurs because heat and light are given off.
D
A physical change occurs because vapor is released into the air.
10

The chemical formula below shows how salt is produced.HCl + NaOH NaCl + H2O Which substances are the reactants?

Question illustration
A
HCl and NaCl
B
NaCl and H2O
C
HCl and NaOH
D
NaOH and H2O

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