Matter—Properties and Changes
2 Changes in Matter
REVIEW
VOCABULARY
observation
Recall the definition of the Review Vocabulary term.
observation
orderly, direct information gathered about a phenomenon
NEW VOCABULARY
Define each New Vocabulary term.
physical change
physical change
phase change
chemical change
law of conservation
change in a substance that does not alter its
composition
phase change
a transition of matter from one state to another
of mass
chemical change
when one or more substances change into a new
substance
law of conservation of mass
states that mass is neither created nor
destroyed during a chemical reaction
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Science Notebook • Matter—Properties and Changes
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2 Changes in Matter (continued)
Determine which type of change each statement represents. Use P
for physical change and C for chemical change. Explain your answers.
silver spoon tarnishes C
Explanation: a new substance, tarnish, is created
crushing an aluminum can P
Explanation: only the shape of the can changes
freezing water
P
Explanation: only the state of matter changes
burning wood
C
Explanation: a new substance, ash, is created
copper turns a greenish color C
Explanation: a new substance is created
grind coffee beans
P
Explanation: only the size and shape of the beans change
Describe how iron turns into a brownish-red powder. Name the
reactants and product that are involved.
Iron reacts with oxygen in the air to form rust. The reactants are iron and
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oxygen. The product is rust.
Get It?
Define chemical change.
A chemical change is the change of one or more substances into
new substances.
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2 Changes in Matter (continued)
Summarize Fill in the blanks to help you take notes while you read
Example Problem 1.
Problem
The total
mass
reactants
equal
of the products must
. This shows the law of
the total mass of the
conservation of mass
.
1. Analyze the Problem
mass of mercury(II) oxide = 10.00 g
Known:
liquid mercury = 9.26 g
Unknown:
mass of oxygen formed
2. Solve for the Unknown
Write an equation showing conservation of mass of reactants and
products.
mass of mercury(II) oxide = mass of mercury + mass of oxygen
Write an equation to solve for the mass of oxygen.
mass of oxygen = mass of mercury(II) oxide − mass of mercury
Substitute known values and solve.
Mass of oxygen = 10.00 g − 9.26 g
Mass of oxygen = 0.74
g
Write an equation that shows that the mass of the two products
equals the mass of the reactant.
9.26
g mercury + 0.74
g oxygen = 10.00 g mercury(II) oxide
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3. Evaluate the Answer
2 Changes in Matter (continued)
CHECK YOUR PROGRESS
10. Classify each change as physical or chemical.
a. crushing an aluminum can
b. recycling used aluminum cans to make new ones
c. aluminum combining with oxygen to form aluminum oxide
a. physical b. physical c. chemical.
11. Describe the results of a physical change and list three examples of physical change.
During a physical change, a substance is altered, but its composition does not change. Examples
will vary but might include changes such as melting, freezing, boiling, bending, and tearing.
12. Describe the results of a chemical change. List four indicators of chemical change.
During a chemical change, the composition of a substance is altered. Possible indicators of chemical
change include a change in color, odor, or temperature, and the formation of a gas or solid from a
liquid.
13. Calculate Solve each of the following.
a. If 22.99 g of sodium and 35.45 g of chlorine fully react, how much sodium
chloride forms?
b. A 12.2-g sample of X reacts with a sample of Y to form 78.9 g of XY. What mass
of Y reacted?
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a. 58.44 g of sodium chloride b. 66.7 g of Y
14. Evaluate A friend tells you, “Because composition does not change during a
physical change, the appearance of a substance does not change.” Is your friend
correct? Explain.
The statement is incorrect. While the composition does not change, a change in appearance often
accompanies a physical change.
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