Forms Of Energy Page 2
ADVERTISEMENT
1
2
3Review and Assessment
Checking Concepts
11.
Compounds—pure substances made up
of two or more elements chemically
Checking Concepts
combined; elements combined in a specific
ratio; properties differ from those of
What are three ways that compounds and
18.
Ratios
The elements phosphorus and oxygen
11.
combined elements
form a compound with the formula P
O
.
mixtures differ?
2
5
What is the ratio of phosphorus atoms to
Mixtures—not pure substances; made up of
How does a physical change differ from a
12.
oxygen atoms in the compound?
two or more elements and/or compounds
chemical change?
not chemically combined; parts not
How are changes in matter related to changes
13.
combined in a specific ratio; mixed
in energy?
substances retain individual properties
Use the information and the diagrams below
How do you know that the burning of candle
14.
to answer Questions 19–22.
12.
In a physical change, the same substance
wax is an exothermic change?
Each diagram below represents a different kind of
is present before and after the change. In a
Thinking Critically
matter. Each ball represents an atom. Balls of the
chemical change, new substances are
same color represent the same kind of atom.
produced.
Which of the following is a
15.
Classifying
A
B
13.
Every physical or chemical change in
solution: pure water, fruit punch, cereal and
milk in a bowl? Explain how you know.
matter includes a change in energy.
16.
Problem Solving
Suppose you dissolve some
14.
The burning wax releases energy in the
table salt in a glass of water. How could you
form of light (electromagnetic energy) and
prove to someone that the dissolving was a
heat (thermal energy). A change that gives
physical change, not a chemical change?
off energy is an exothermic change.
17.
Interpreting Graphs
A student has two
C
D
liquids at the same temperature. The liquids
Thinking Critically
react with one another when mixed. The
15.
Fruit punch is a solution because its
graph below shows the change in temperature
after the two liquids are mixed. Did the
parts retain their individual properties but
reaction absorb or release thermal energy?
are evenly mixed.
Explain your answer.
16.
Sample answer: The solution would
taste salty so the salt would still be present.
Reaction Temperature vs. Time
Boiling the liquid separates the water from
Which diagrams
19.
Interpreting Diagrams
28
represent a single element? Explain.
the salt.
Which diagrams represent pure
20.
Classifying
17.
The reaction released energy. The
26
substances? Explain.
temperature of the reaction mixture
How do the molecules in
21.
Interpreting Data
increased.
24
diagram A differ from those in diagram D?
Math Practice
Which diagram
22.
Interpreting Diagrams
22
represents a mixture? Explain.
18.
2 : 5; the compound P
O
has two atoms
2
5
of phosphorus for every five atoms of
20
0
10
20
30
40
50
60
oxygen.
Time (s)
Applying Skills
Performance Assessment
Compare the changes
Diagrams A and B represent single
you recorded in your log with those of your
19.
classmates. Defend your opinions as to whether or
elements because each is made up of a single
not your observations describe physical or
type of atom.
chemical changes.
20.
Diagrams A, B, and D represent pure
82 ◆
substances. Diagrams A and B represent
elements. Diagram D represents a
compound because its two kinds of atoms
are chemically combined in a set ratio.
A—a single kind of atom; D—two kinds
21.
of atoms
22.
Diagram C represents a mixture because
it contains several different kinds of
substances that are not chemically combined.
82
ADVERTISEMENT
0 votes
Related Articles
Related forms
Related Categories
Parent category: Education