5 The Skin

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Section
5
5
The Skin
The Skin
Objectives
Reading Preview
After this lesson, students will be able to
D.1.5.1 Describe the functions and the
structures of skin.
D.1.5.2 Identify habits that can help keep
skin healthy.
Key Concepts
• What are the functions and the
structures of skin?
• What habits can help keep your
skin healthy?
Key Terms
Target Reading Skill
Identifying Main Ideas Explain that
identifying main ideas and details helps
students sort the facts from the information
into groups. Each group can have a main
topic, subtopics, and details.
Answers
Sample details:
The skin forms a barrier against diseasecausing microorganisms and harmful
substances, and prevents the loss of
important fluids; the skin helps the body
maintain a steady temperature; the skin
helps to eliminate wastes through
perspiration; the skin contains nerves that
gather information about the environment;
skin cells produce vitamin D that helps your
body absorb calcium.
• epidermis • melanin
• dermis • pore • follicle
• cancer
Target Reading Skill
Identifying Main Ideas As you
read the section titled The Body's
Tough Covering, write the main
idea—the biggest or most
important idea—in a graphic
organizer like the one below. Then,
write five supporting details. The
supporting details give examples of
the main idea.
Main Idea
The skin has several important
functions.
Detail
Detail
Detail
What Can You Observe About Skin?
1. Using a hand lens, examine the skin on your hand. Look for
pores and hairs on both the palm and back of your hand.
2. Place a plastic glove on your hand. After
five minutes, remove the glove. Then,
examine the skin on your hand with the
hand lens.
Think It Over
Inferring Compare your hand
before and after wearing the
glove. What happened to the skin
when you wore the glove? Why did
this happen?
Here’s a question for you: What’s the largest organ in the
human body? If your answer is the skin, you are right! If an
adult’s skin were stretched out flat, it would cover an area
larger than 1.5 square meters—about the size of a mattress on
a twin bed. You may think of the skin as nothing more than a
covering that separates the inside of the body from the outside
environment. If so, you’ll be surprised to learn about the many
important roles that the skin plays.
The Body’s Tough Covering
The skin performs several major functions in the body. The
skin covers and protects the body from injury, infection, and
water loss. The skin also helps regulate body temperature,
eliminate wastes, gather information about the environment, and produce vitamin D.
Teaching Resources
• Transparency D9
Preteach
Protecting the Body The skin protects the body by form-
Build Background
Knowledge
ing a barrier that keeps disease-causing microorganisms and
harmful substances outside the body. In addition, the skin
helps keep important substances inside the body. Like plastic
wrap that keeps food from drying out, the skin prevents the
loss of important fluids such as water.
L1
What Skin Does
Have students look at the skin on their arms
and hands. Ask them to speculate about
what they think their skin does. (Sample
answers: It protects body tissues underneath,
keeps bacteria out of the body, produces
sweat, and provides feeling through the sense
of touch.)
328 ◆
L1
Skills Focus Inferring
Materials hand lens, plastic gloves
Time 15 minutes
Tips Ask students to predict what
structures they expect to see on the surface
of their skin.
328
Expected Outcome Students will
observe perspiration, hairs on the back
of the hands, and ridges.
Think It Over After students have worn the
plastic glove, moisture covering the skin’s
surface will be noticeable. Perspiration is
one of the functions of the skin.
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Maintaining Temperature Another function of the skin is
to help the body maintain a steady temperature. Many blood
vessels run throughout the skin. When you become too warm,
these blood vessels enlarge and the amount of blood that flows
through them increases. These changes allow heat to move
from your body into the outside environment. In addition,
sweat glands in the skin respond to excess heat by producing
perspiration. As perspiration evaporates from your skin, your
skin is cooled.
Instruct
The Body’s Tough
Covering
Teach Key Concepts
L1
The Functions of Skin
Focus Have students look at the other
people in the class. Ask: What is the most
obvious function of skin? (To cover and
protect the body)
Teach Explain that the skin keeps out
harmful microorganisms and substances
and keeps in fluids, but skin has other
functions, too. Ask: How does skin regulate
temperature? (When you are too warm,
blood vessels in the skin enlarge to allow heat
to move out of your body. The evaporation of
perspiration cools the skin.) How is
waste eliminated by the skin? (Through
perspiration) What information can you
gather from the environment through your
skin? (Pressure, pain, and temperature) How
does your skin help you to have healthy
bones? (Some skin cells produce vitamin D
that helps your digestive system to absorb
calcium, which is needed for strong bones.)
Apply Ask students to identify how each
function of skin helps the body maintain
homeostasis—for example, helping to
maintain water balance. learning
Eliminating Wastes Perspiration contains dissolved waste
materials that come from the breakdown of chemicals during
cellular processes. Thus, your skin is also helping to eliminate
wastes whenever you perspire. For example, some of the wastes
that come from the breakdown of proteins are eliminated in
perspiration.
Gathering Information The skin also gathers information
about the environment. To understand how the skin does this,
place your fingertips on the skin of your arm and press down
firmly. Then lightly pinch yourself. You have just tested some
of the nerves in your skin. The nerves in skin provide information about such things as pressure, pain, and temperature. Pain
messages are important because they warn you that something
in your surroundings may have injured you.
Producing Vitamin D Lastly, some of the skin cells produce vitamin D in the presence of sunlight. Vitamin D is
important for healthy bones because it helps the cells in your
digestive system to absorb the calcium in your food. Your skin
cells need only a few minutes of sunlight to produce all the
vitamin D you need in a day.
How does your skin gather information about the
environment?
FIGURE 18
Eliminating Wastes
Sweat glands in the skin produce
perspiration, which leaves the body
through pores. The inset photo
shows beads of sweat on skin.
Relating Cause and Effect In
addition to eliminating wastes,
what is another important function
of perspiration?
modality: verbal
Independent Practice
L2
Teaching Resources
• Guided Reading and Study Worksheet:
The Skin
Student Edition on Audio CD
Chapter 8 ◆ 329
Differentiated Instruction
L1
Special Needs
Demonstrating Skin Functions Gently
squeeze students’ hands, and explain that
the nerves in skin help them to feel the
pressure. Rub a piece of ice on their skin
to demonstrate that the skin senses
temperature. Ask: What happens to your
skin when you feel cold? (You get goose
bumps.) Have students dip a finger into a
cup of water, then hold the finger in the air.
Ask: How does your finger feel? (Cool)
Explain that this is like what happens when
people sweat. The sweat, like the water,
removes heat from your body and makes
you feel cooler. learning modality:
kinesthetic
Monitor Progress
L2
Skills Check Have students create concept
maps of the skin’s functions.
Answers
Figure 18 As perspiration evaporates from
the skin, heat moves from the body into the
environment.
Nerves in skin provide
information about pressure,
pain, and temperature.
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Help Students Read
L1
SQ3R Have students survey the diagrams,
photos, and graph in this section, and write a
short explanation of each. Then have them
write questions, read the section, recite
their questions, and give the answers in their
own words. Tell students to review the
section by writing their answers, and then
answer the Key Concepts questions on the
first page of the section. For more
information on SQ3R, refer to the Content
Refresher.
Pore
Hair
Oil gland
Epidermis
Sweat
droplet
Dermis
Fat
The Epidermis
FIGURE 19
Teach Key Concepts
The skin is made of two main
Sweat gland
layers. The top layer is called the
epidermis. The bottom layer is
called the dermis.
Interpreting Diagrams In which
layer of the skin do you find blood
The skin
vessels?
The Skin
L1
The First Layer of Skin
Focus Tell students that the epidermis is
the layer of skin you can see.
Teach Refer students to Figure 19. Ask:
What is the epidermis made of? (A layer of
dead cells) How do these dead cells protect
you? (The dead cells on your fingertips cushion
the fingertips, shedding of dead cells carries
away bacteria, and some cells produce hard
fingernails.)
Apply Ask: What is the advantage of
having dead cells make up the outer layer
of skin instead of living tissue? (Living tissue
has nerves and blood vessels. You would feel
pain more easily from cuts and pressure.
You would bleed more easily.) learning
Blood vessels
Hair follicle
Nerve
The Epidermis
is organized into two main layers, the epidermis
and the dermis. The epidermis is the outer layer of the skin. In
most places, the epidermis is thinner than the dermis. The epidermis does not have nerves or blood vessels. This is why you
usually don’t feel pain from very shallow scratches, and why
shallow scratches do not bleed.
Epidermis Structure Like all cells, the cells in the epidermis have a life cycle. Each epidermal cell begins life deep in the
epidermis, where cells divide to form new cells. The new cells
mature and move upward in the epidermis as new cells form
beneath them. After about two weeks, the cells die and become
part of the epidermal surface layer. Under a microscope, this
surface layer of dead cells resembles flat bags laid on top of one
another. Cells remain in this layer for about two weeks. Then,
they are shed and replaced by the dead cells below.
modality: verbal
Teaching Resources
Epidermis Function In some ways, the cells of the epidermis are more valuable dead than alive. Most of the protection
provided by the skin is due to the layer of dead cells on the surface. The thick layer of dead cells on your fingertips, for example, protects and cushions your fingertips. Also, the shedding
of dead cells carries away bacteria and other substances that
settle on the skin. Every time you rub your hands together, you
lose thousands of dead skin cells and any bacteria on them.
• Transparency D10
330 ◆
Differentiated Instruction
L1
English Learners/Beginning
Vocabulary: Word Knowledge
Contrast the meanings of dermis and
epidermis. Point out that dermis means
“skin” and the prefix epi means “outside.”
Ask students to relate these terms. (The
epidermis is on the outside of the dermis.)
learning modality: verbal
L2
English Learners/Intermediate
Vocabulary: Science Glossary
Pronounce the key terms epidermis, dermis,
pores, and follicles as you point to them
in Figure 19. Have students write the
definition of each of those terms in their
science glossaries, and draw and label their
own diagrams of the structures. learning
modality: verbal
330
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The Dermis
Teach Key Concepts
Hair follicle
Sweaty Skin
This activity illustrates one of
the skin’s functions.
1.
Some cells in the inner layer of the epidermis help to protect the body, too. On your fingers, for example, some cells
produce hard fingernails, which protect the fingertips from
injury and help you scratch and pick up objects.
Other cells deep in the epidermis produce melanin, a pigment, or colored substance, that gives skin its color. The more
melanin in your skin, the darker it is. Exposure to sunlight
stimulates the skin to make more melanin. Melanin production helps to protect the skin from burning.
Wrap a wet cotton
ball around the bulb
of one thermometer. Place
a second thermometer
next to the first one.
What is the function of pores in the skin?
The Second Layer of Skin
Focus Refer students to Figure 19.
Teach Ask students to note differences
between the epidermis and the dermis.
(The dermis is thicker. It has blood vessels,
nerves, hair follicles, sweat glands, and fat.)
What are the functions of the dermis?
(The fat pads internal organs and helps keep
heat in the body. Sweat glands produce
perspiration. Oil helps moisten the skin.)
Apply Ask: How does the dermis help
regulate temperature when you are hot?
(It contains blood vessels that widen to help
move heat from the body.) Ask students to
infer what happens to blood vessels in the
dermis when a person is cold. (They narrow
to conserve heat.) learning modality:
verbal
Use Visuals: Figure 19
The Dermis
The dermis is the inner layer of the skin. Find the dermis in
Figure 19. Notice that it is located below the epidermis and
above a layer of fat. This fat layer pads the internal organs and
helps keep heat in the body.
The dermis contains nerves and blood vessels. The dermis
also contains sweat glands, hairs, and oil glands. Sweat glands
produce perspiration, which reaches the surface through openings called pores. Strands of hair grow within the dermis in
structures called follicles (FAHL ih kulz). The hair that you see
above the skin’s surface is made up of dead cells. Oil produced
in glands around the hair follicles help to waterproof the hair.
In addition, oil that reaches the surface of the skin helps to
keep the skin moist.
L2
2. After two minutes, record
the temperature reading
on each thermometer.
3. Using a piece of card–
board, fan both of the
thermometers for several
minutes. The cardboard
should be at least 10 cm
from the thermometers.
Record the temperatures.
Measuring Which of the
thermometers had a lower
temperature after Step 3?
How does this activity relate
to the role of skin in regulating body temperature?
L1
Epidermis and Dermis
Focus Ask students to identify the openings
in the epidermis. (Pores and openings of
hair follicles)
Teach Ask: What are the pores connected
to? (Sweat glands) Where is oil produced?
(In glands around the hair) Call students’
attention to the inset of the hair. Ask:
What are the scalelike structures? (Dead
epidermal cells)
Apply Ask students to infer the relationship
between the hairs and the nerves in the
dermis. (When something touches or blows
against the hairs, the nerves pick up the
sensation.) learning modality: visual
Chapter 8 ◆ 331
Monitor Progress
L2
Skills Focus Measuring
Materials 2 thermometers, wet cotton
ball, piece of cardboard
Time 15 minutes
Tips
CAUTION: Advise students to use care
when handling the thermometers.
Have students note the temperatures on
both thermometers before beginning.
Expected Outcome The thermometer
wrapped in wet cotton has a lower
temperature after it is fanned. When skin is
moist, sweat evaporates, removing body
heat and lowering the body temperature.
Extend Ask students why they might put
on a heavy sweatshirt after vigorous
physical activity. (To keep from getting
chilled when sweat evaporates) learning
L2
Writing Have students write paragraphs
that compare and contrast the structure and
function of the dermis and epidermis.
Answers
Figure 19 The dermis
They are the openings
through which perspiration
from sweat glands in the dermis reaches the
skin’s surface.
modality: logical/mathematical
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Caring for Your Skin
Sunscreens and Sunburn
Download a worksheet that will guide students’ review
of Internet resources on the skin.
Teach Key Concepts
L2
Habits to Keep Skin Healthy
Focus Tell students that acne is the most
common skin problem for teens.
Teach Ask: What is a healthful habit to
help control acne? (Keep your face clean.)
What are other habits to care for your
skin? (Eat a well-balanced diet, drink
plenty of water, and protect your skin from
sun damage.)
Apply Tell students that people with acne
should wash their face twice a day with a
mild cleanser. More frequent washing or
scrubbing with strong soap or scrub pads
can make acne worse. learning modality:
The graph shows how sunscreens with
different sun protection factor (SPF) ratings
extend the time three people can stay in the
sun without beginning to get a sunburn.
1. Reading Graphs What does the height of
each bar in the graph represent?
2. Interpreting Data How long can Person B
stay in the sun without sunscreen before
starting to burn? With a sunscreen of
SPF 4? SPF 15?
3. Inferring Suppose that Person C was
planning to attend an all-day picnic. Which
sunscreen should Person C apply? Use data
to support your answer.
4. Calculating Which is more effective at
preventing sunburn—a sunscreen with
SPF 4 or one with SPF 15? How much
more effective is it? Show your work.
332
No sunscreen
SPF 4
SPF 15
10
5
0
A
B
C
Person
5. Drawing Conclusions What does the
number in the SPF rating stand for? (Hint:
Note the length of time each person can
stay in the sun without sunscreen and
compare this value to the length of time
each can stay in the sun using SPF 4. Then,
do the same for SPF 15.)
Caring for Your Skin
Because your skin has so many vital functions, taking care of it
is important. Three simple habits can help you keep your skin
healthy. Eat a healthful diet. Keep your skin clean and dry.
Limit your exposure to the sun.
verbal
Math Skills Making and interpreting
graphs
Focus Remind students that wearing
sunscreen is one way to reduce the risk
of skin cancer.
Teach Tell students that the skin’s relative
resistance to sunburn, as well as the strength
of sunscreen used, affects how long you can
safely stay in the sun. However, limiting sun
exposure is recommended for everyone as
the best method of preventing overexposure.
Answers
1. The height of each bar represents the
amount of time that person can spend in
the sun before burning.
2. 20 minutes; 80 minutes; 5 hours
3. Person C would need to use SPF 15
sunscreen because SPF 4 would protect the
individual for only four hours.
4. SPF 15 is 3.75 times more effective at
preventing sunburn. Calculations:
2.5 hours compared to 40 minutes, or
150 minutes/40 minutes = 3.75; 5 hours
15
Sunscreen Ratings
Time Before Burning
(hours)
For: Links on the skin
Visit: www.SciLinks.org
Web Code: scn-0415
Healthful Diet Your skin is always active. Eating a wellbalanced diet provides the energy and raw materials needed for
the growth and replacement of hair, nails, and skin cells. In
addition to what you eat, a healthful diet also includes drinking plenty of water. That way, you can replace the water lost in
perspiration.
For: Links on the skin
Visit: www.SciLinks.org
Web Code: scn-0415
Keeping Skin Clean When you wash your skin with mild
soap, you get rid of dirt and harmful bacteria. Washing your
skin also helps to control oiliness.
Good washing habits are particularly important during
the teenage years when oil glands are more active. When
glands become clogged with oil, the blackheads and whiteheads of acne can form. If acne becomes infected by skin bacteria, your doctor may prescribe an antibiotic to help control
the infection.
332 ◆
compared to 80 minutes, or 300 minutes/
80 minutes = 3.75
5. It stands for the level of protection against
sunburn—the higher the level is, the greater
the protection. SPF 4 means a person can
safely stay four times as long in the sun;
SPF 15—15 times as long.
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Limiting Sun Exposure It is important to
protect your skin from the harmful effects of
the sun. Repeated exposure to sunlight can
damage skin cells, and possibly lead to skin cancer. Cancer is a disease in which some cells in
the body divide uncontrollably. In addition,
repeated exposure to the sun can cause the skin
to become leathery and wrinkled.
There are many things you can do to protect
your skin from damage by the sun. When you
are outdoors, always wear a hat, sunglasses, and
use a sunscreen on exposed skin. Choose clothing made of tightly woven fabrics for the greatest protection. In addition, avoid exposure to
the sun between the hours of 10 A.M. and 4 P.M.
That is the time when sunlight is the strongest.
Monitor Progress
L2
Answers
Figure 20 Wearing sunscreen and avoiding
exposure to the sun between 10 A.M. and
2 P.M.
Damage to skin cells, cancer,
and wrinkled, leathery skin.
Assess
Reviewing Key Concepts
1. a. The skin protects the body from injury,
What health problems can result
from repeated sun exposure?
FIGURE 20
Skin Protection
This person is wearing a hat to
protect his skin from the sun.
Applying Concepts What other
behaviors can provide protection
from the sun?
5
Section 5 Assessment
Target Reading Skill Identifying Main Ideas Use your
graphic organizer to help you answer Question 1 below.
Reviewing Key Concepts
1. a. Listing What are five important functions of the skin?
b. Identifying How does the epidermis protect the body?
What structure in the dermis helps to maintain body
temperature?
c. Inferring What could happen if the pores in your
dermis become blocked?
2. a. Identifying What are three things you can do to keep
your skin healthy?
b. Explaining Why is it important to use sunscreen to
protect your skin when outside?
c. Making Judgments Do you think it is possible to wash
your skin too much and damage it as a result? Why or
why not?
Protection From the Sun With a
family member, look for products
in your home that provide protection from the sun. You may also
want to visit a store that sells these
products. Make a list of the products and place them in categories,
such as sunblocks, clothing, eye
protectors, and other forms of protection. Explain to your family
member why it is important to use
such products.
Chapter 8 ◆ 333
infection, and water loss; helps regulate body
temperature; eliminates waste; gathers
information about the environment; and
produces vitamin D. b. The epidermis
consists of a layer of dead cells that protect
the inner parts of the skin. The dermis
contains a fat layer that helps keep in heat
and sweat glands that help cool the body.
c. If pores in the dermis become blocked the
blackheads and whiteheads of acne can form.
2. a. Accept any three: Eat properly, drink
enough water, limit exposure to the sun, and
keep skin clean and dry. b. It is important
to use sunscreen when outdoors because
unprotected skin can burn. Also, repeated
exposure to sunlight can damage skin cells,
causing them to become cancerous. c. Sample
answer: Washing the skin too much may
cause dryness and remove dead skin cells
that are necessary to protect the skin.
Reteach
L1
Use Figure 19 to review how each structure
relates to the function of the skin.
Performance Assessment
Writing Have students develop a pamphlet
explaining to other teens how to take care of
their skin.
Teaching Resources
• Section Summary: The Skin
• Review and Reinforce: The Skin
• Enrich: The Skin
Protection From the Sun L2 Before
students perform this activity, have
them identify ways that people protect
themselves from the sun. Encourage
students to include items such as hats,
sunglasses, and beach umbrellas.
333
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Sun Safety
L2
Prepare for Inquiry
Key Concept
The higher a product’s SPF rating, the better
it protects individuals from the sun.
Skills Objectives
After this lab, students will be able to
• observe the effectiveness of different levels
of sun protection
• predict which sunscreen provides more
protection
• interpret data on which fabrics protect
against sun exposure
• draw conclusions about which fabric
provided the most protection
Prep Time 20 minutes
Class Time 45 minutes, follow-up
20 minutes
Advance Planning
• Obtain photosensitive paper from science
supply houses, or a toy or craft store.
• Collect fabric or have students bring in
scraps of fabric. Choose fabrics commonly
worn by students, such as T-shirt material
and denim.
• Before the activity, test a strip of
photosensitive paper in the window of
your classroom, if present, to determine
whether UV rays pass through that
particular glass.
Safety
Remind students to be careful
when using scissors. Caution
them not to get any sunscreen into their eyes
or mouths. Advise them to wash their hands
after the lab. If sunlamps are used, be sure
students do not look at the light source and
if possible, provide UV-protective goggles.
Review the safety guidelines in Appendix A.
Teaching Resources
• Lab Worksheet: Sun Safety
Sun Safety
Problem
How well do different materials protect the skin
from the sun?
Skills Focus
observing, predicting, interpreting data,
drawing conclusions
Materials
• scissors
• photosensitive paper
• metric ruler
• white construction paper
• stapler
• pencil
• resealable plastic bag
• plastic knife
• 2 sunscreens with SPF ratings of 4 and 30
• staple remover
• 3 different fabrics
Procedure
PART 1
Sunscreen Protection
1. Read over the procedure for Part 1. Then,
write a prediction about how well each of
the sunscreens will protect against the sun.
2. Use scissors to cut two strips of photosensitive paper that measure 5 cm by 15 cm.
3. Divide each strip into thirds by drawing lines
across the strips.
4. Cover one third of each strip with a square of
white construction paper. Staple each square
down.
5. Use a pencil to write the lower SPF rating on
the back of the first strip. Write the other SPF
rating on the back of the second strip.
7. With a plastic knife, spread a thin layer of
each sunscreen on the bag over the bottom
square of its labeled strip. This is shown in
the photo above. Make certain each strip has
the same thickness of sunscreen. Be sure not
to spread sunscreen over the middle squares.
8. Place the strips in sunlight until the color of
the middle squares stops changing. Make
sure the bag is sunscreen-side up when you
place it in the sunlight.
9. Remove the staples from the bag, and then
take out the strips. Take off the construction
paper. Rinse the strips for one minute in cold
water, then dry them flat.
10. Observe all the squares. Then, record your
observations.
334 ◆
Guide Inquiry
Introduce the Procedure
• Demonstrate how to cut the
photosensitive and construction paper
strips and staple them in place in the
plastic bag. Demonstrate the technique for
coating the bag with sunscreen.
334
6. Place the two strips side by side in a plastic
bag. Seal the bag, then staple through the
white squares to hold the strips in place.
• Check that students understand that the
white construction paper allows them to
control the experiment and compare their
results. Ask: What are some other
controls? (Using the same amount of
sunscreen and making sure the strips are
exposed to direct sunlight)
sx05_TE_(nc7-8)c01D.fm Page 335 Tuesday, June 7, 2005 4:51 PM
• Place the strips where they will receive
direct sunlight. You could use an artificial
source of ultraviolet light such as a
sunlamp.
PART 2
Fabric Protection
11. Your teacher will provide three fabric pieces
of different thicknesses.
12. Based on the procedure in Part 1, design an
experiment to test how effective the three
fabrics are in protecting against the sun.
Write a prediction about which fabric you
think will be most effective, next most effective, and least effective.
13. Obtain your teacher’s approval before carrying out your experiment. Record all of your
observations.
Analyze and Conclude
1. Observing Did the sunscreens protect
against sun exposure? How do you know?
2. Predicting Which sunscreen provided more
protection? Was your prediction correct?
How would you predict a sunscreen with an
SPF of 15 would compare to the sunscreens
you tested?
3. Interpreting Data Did the fabrics protect
against sun exposure? How do you know?
4. Drawing Conclusions Which of the fabrics
provided the most protection? The least protection? How did your results compare with
your predictions?
5. Communicating What advice would you give
people about protecting their skin from the
sun? Create a pamphlet in which you address
this question by comparing the different sunscreens and fabrics you tested.
More to Explore
Design another experiment, this time to find out
whether ordinary window glass protects skin
against sun exposure. Obtain your teacher’s permission before carrying out your investigation.
Expected Outcome
The sunscreens with the highest SPF and the
materials with the tightest weave provide the
most protection.
Analyze and Conclude
1. Yes; sections not covered by sunscreen
changed color drastically. The covered
sections changed color slightly or not at all.
2. The sunscreen with SPF 30 provided more
protection. Yes, if students predicted this
result. A sunscreen with an SPF of 15 would
provide more protection than SPF 4 but less
protection than SPF 30.
3. Yes; the sections covered by fabric did not
change color as much as the uncovered areas.
4. The heaviest or most tightly woven fabric,
such as denim, provided the most
protection. Thin fabrics, such as T-shirt
material or light gauze, provided the least
protection. Sample answer: My predictions
matched the results.
5. Sample answer: Wear sunscreen, limit
exposure to the sun, and wear clothing that
blocks the sun. The pamphlet should include
choosing a sunscreen with a high SPF rating
and wearing clothing that blocks the sun.
(You may want to share with students that
lightweight clothing specially made to block
UV rays is available.)
Extend Inquiry
More to Explore Students’ designs should
include placing one strip of photosensitive
paper in direct sunlight and one on an inside
window sill or under a piece of window glass.
Check that students control variables such as
the angle and amount of sunlight received.
Chapter 8
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