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