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Standards-Based Assessment
TEST PRACTICE
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Analyzing Theories
8.5.b
Answer the questions based on the information in the following passage.
During the 1700s, scientists thought that matter contained a substance called
phlogiston. According to this theory, wood was made of phlogiston and ash. When
wood burned, the phlogiston was released and the ash was left behind.
The ash that remained had less mass than the original wood. This decrease in
mass was explained by the release of phlogiston. However, when substances such as
phosphorus and mercury burned, the material that remained had more mass than
the original substances. This increase in mass did not make sense to some scientists.
The scientists who supported the phlogiston theory said that the phlogiston in
some substances had negative mass. So, when the substances burned, they released
phlogiston and gained mass. Other scientists disagreed, and their research led to the
discovery of a scientific law. Antoine Lavoisier carried out several experiments by
burning metals in sealed containers. He showed that mass is never lost or gained in a
chemical reaction.
1. What did the phlogiston theory successfully
explain?
a. the presence of ash in unburned wood
b. the apparent gain of mass in some reactions
c. the chemical makeup of the air
d. the apparent decrease in mass in some situations
2. Why did some scientists disagree with the
phlogiston theory?
a. Burning a substance always produced an
increase in mass.
b. Burning a substance always produced a
decrease in mass.
c. Burning could produce either an increase or
decrease in mass.
d. Burning wood produced ash and phlogiston.
Extended Response
Answer the following questions in detail.
Include some of the terms from the list on the right.
Underline each term you use in your answers.
5. Suppose you wanted to change the rate of a
chemical reaction. What might you change in the
reaction? Explain each factor.
3. What law did Lavoisier’s work establish?
a. conservation of energy
b. conservation of mass
c. conservation of momentum
d. conservation of resources
4. To carry out his experiments, what kind of
equipment did Lavoisier need?
a. devices to separate the different elements in
the air
b. machines that could separate wood from ash
c. microscopes that could be used to study rust
and ash
d. balances that could measure mass very
accurately
catalyst
temperature
surface area
coefficient
reaction
concentration
subscript
6. Is the chemical equation shown below balanced?
Why or why not? How are balanced chemical
equations related to conservation of mass?
C6H12O6 + O2
6CO2 + 6H2O
Chapter 9: Chemical Reactions 299
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