Name
Section
Date
8.2
Pressure
Summary
Textbook pages 290–299
Before You Read
What do you think pressure is? What might happen if you apply pressure to a solid,
liquid, or gas? Write your ideas in the lines below.
_______________________________________________________________________________________
_______________________________________________________________________________________
✏
◆
What is pressure?
Mark the Text
In Your Own Words
Highlight the main idea in
each paragraph. Stop after
each paragraph and put
what you just read into your
own words.
Pressure is the amount of force that acts on a given area of
an object. Think about writing with a sharp pencil and a dull
pencil. Which puts more pressure on the paper if you press
down with the same amount of force? The sharp pencil does.
It concentrates the force into a smaller area than does the dull
pencil.
How does pressure affect matter?
✔
●
Reading Check
1. Why can you compress a
gas but not a liquid or a
solid?
___________________
___________________
___________________
Pressure can cause a gas to be compressed. Picture the
particles of air inside a balloon. Air is a gas, so its particles
are spread far apart. What happens if you squeeze or press
down on the balloon? Its shape changes. This happens
because the increased pressure on the balloon pushes the air
particles closer together. As a result, the air in the balloon
takes up a smaller volume. In other words, the balloon is
compressed. Compression is a decrease in the volume of
matter caused by a force.
Gases are easy to compress, because the particles of a gas
are spread far apart. What about liquids and solids? The
particles that make up liquids and solids are very close together.
There is little room to push them closer to decrease their
volume. So liquids and solids normally do not compress very
much. ●
✔
What happens when a gas-filled container explodes?
The particles of a gas move faster and farther apart when
energy is added. As a result, the gas expands. If the heated
gas is trapped inside a container, the gas particles bounce
against the sides faster and more often. This means that the
heated gas exerts more pressure on the inside of the container.
This added pressure can lead to an explosion.
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Pressure
© 2006 McGraw-Hill Ryerson Limited
Section
Name
8.2
Date
Summary
continued
How is pressure measured?
Recall that pressure is the amount of force on an area. You
can write this as a formula:
force (F)
F
pressure (P) = , or P = area (A)
A
What units are used for F (force) and A (area)? Recall from
section 8.1 that force is measured in newtons (N). Recall that
area is often measured in square metres (m2). Pressure is
✔
measured in units of newtons per square metre, or N/m2. ●
2
A pressure that is equal to 1 N/m is called a pascal,
which has the symbol Pa (1 Pa = 1 N/m2). This is a very
small amount of pressure. Therefore, pressure is often
measured using a unit equal to 1000 Pa. This unit is called a
kilopascal. It has the symbol kPa (1 kPa = 1000 Pa).
A
✔
●
Reading Check
2. What is the formula for
pressure?
___________________
B
plastic bottle filled
with a gas
C
Gases are
easily compressed.
D
plastic bottle filled
with a liquid
© 2006 McGraw-Hill Ryerson Limited
Liquids are extremely
difficult to compress.
Section 8.2
Pressure • MHR
117
Name
Date
Cloze
Activity
Section 8.2
Use with textbook pages 290–296.
What is pressure?
Vocabulary
liquids
m2
N
N/m2
Pa
pascal
pressure
solids
volume
area
compression
decreases
explosion
force
gases
increases
kilopascal
kPa
Use the terms in the vocabulary box to fill in the blanks. You can use the terms
more than once. You will not need to use every term.
1. ________________________________________ is the amount of force that acts on a
given area of an object.
2. ________________________________________ is a decrease in the volume of matter
caused by a force. Pressure can cause a gas to be compressed. As a result, the
volume of the gas ________________________________________.
3. ________________________________ are easy to compress, because their particles are
spread far apart.
4. If the heated gas is trapped inside a container, the gas particles bounce against the
sides faster and more often. This means that the heated gas exerts more
________________________________________ on the inside of the container. This
added pressure can lead to a(n)________________________________________.
F
5. In the formula P = A, P stands for________________________________________,
F stands for________________________________________, and A stands for
________________________________________.
6. Force is measured in ________________________________________.
Area is often measured in ________________________________________.
7. A pressure that is equal to 1 N/m2 is called a___________________________________.
It has the symbol _________________________________________.
8. Pressure is often measured in units 1000 Pa, which is called a ____________________.
It has the symbol _________________________________________.
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MHR • Section 8.2
Pressure
© 2006 McGraw-Hill Ryerson Limited
Name
Illustrating
Concepts
Section 8.2
Date
Use with textbook pages 290–296
Compression
Draw diagrams to help explain the statements below. Show what is happening to
the particles in the substances described. Label your diagrams.
1. It is fairly easy to compress a balloon partly filled with air.
2. A sealed can containing a heated gas explodes when the gas inside is heated.
© 2006 McGraw-Hill Ryerson Limited
Section 8.2
Pressure • MHR
119
Name
Applying
Knowledge
Section 8.2
Date
Use with textbook pages 290–296.
Under some pressure
F
The formula for pressure is P = A
The formula for area is A = l × w
Calculate the pressure for each example below. Show all your work, including the
formula(s) that you use.
1.
2.
700 N
147 N
0.75 m
2m
1m
2m
Calculations:
Calculations:
3.
4.
600 N
300 N
75 cm
50 cm
Calculations:
120
MHR • Section 8.2
50 cm
50 cm
Calculations:
Pressure
© 2006 McGraw-Hill Ryerson Limited
Name
Assessment
Section 8.2
Date
Use with textbook pages 290–296.
Pressure
Match the Unit on the left with the Term that
it measures on the right. Each Term may be
used as often as necessary.
Unit
Term
1. ______ pascal (Pa)
2. ______ newton (N)
3. ______ kilopascal
(kPa)
4. ______ metre (m)
5. ______ square
metre (m2)
6. ______ square
centimetre
(cm2)
A. area
B. force
C. length
D. pressure
Circle the letter of the best answer.
7. Which of the following describes what
happens to the particles of air inside a
bottle as pressure is applied?
10. What states of matter are not easily
compressible?
I.
gas
II.
solid
III.
liquid
A. I and II only
B. I and III only
C. II and III only
D. I, II, and III
11. What will happen to the pressure if the
force is decreased?
A. the pressure will increase
B. the pressure will also decrease
C. the pressure will stay the same
D. it depends on the type of force
12. Calculate the amount of pressure exerted
by a large wooden crate that weighs
1200 N and has a base with dimensions
4 m by 4 m.
A. the particles will speed up
A. 0.013 Pa
B. the particles will slow down
B. 75 Pa
C. the particles will move farther apart
C. 150 Pa
D. the particles will move closer together
D. 300 Pa
8. What is compression?
A. a decrease in mass produced by a force
B. an increase in mass produced by a force
C. a decrease in volume produced by a
force
D. an increase in volume produced by a
force
9. Why can a gas be easily compressed?
13. What is pressure?
A. the change in volume produced by a
force
B. the change in mass produced by a force
C. the amount of compression placed on an
object
D. the amount of force that acts on a given
area of an object
A. it has no fixed shape
B. it has no fixed volume
C. its particles have a lot of kinetic energy
D. it has a large amount of space between
its particles
© 2006 McGraw-Hill Ryerson Limited
Section 8.2
Pressure • MHR
121