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This resource has not yet been reviewed. Not Rated Yet. You May Like. Discuss Blog Curriki Newsletter Sign-up. Log in to Your Account. Forgot Username or Password? Don't have an account? Join Now. Are you sure you want to logout? NNIN Nanotechnology Education : The National Nanotechnology Infrastructure Network created a site with links to various teacher resources, including information on continuing education and how to integrate nanotechnology into your curriculum.

North Carolina State University Nanoscale Education Group : This site features research by North Carolina State University's College of Education explores scale, haptics learning through touch , and molecular spintronics, and provides educators with nanotechnology education resources, articles of interest, and research on learning nanoscience.

TryNano : TryNano is a website specifically geared for high school students and teachers who want to learn about nanotechnology. University of Wisconsin-Madison Materials Research Science and Engineering Center Interdisciplinary Education Group : This University of Wisconsin site has a large selection of teaching materials and modules for teachers of various grade levels.

Teachers are also welcome to share their own nanoscience lesson plans here.

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Nanotechnology and Career Knowledge NACK Center : NACK a part of Penn State, listed above as part of Nano4me has designed community-college-level degree programs that support nanotechnology careers in industry and offers professional development programs for educators. The new service includes observations and findings on student proficiency, college STEM degrees, and jobs in science-related occupations. Search Keywords Submit Search.

Skip main navigation Nano. You can find additional, useful resources for teachers on the K Students page Click here for info on the Teaching Nano and Emerging Technologies Network. Now instead of seeing an absorption peak, we see almost complete absorption up to a cut-off wavelength which corresponds to the energy of the band gap. For example, zinc oxide ZnO has a particular band gap minimum energy that can be absorbed.

Thus light with higher frequencies and energies is almost completely absorbed and light with lower frequencies and energies is not absorbed. This leads to an absorption spectra with the characteristic sharp drop shown in Figure 9. Thus the minimum frequency corresponds to a maximum wavelength up to which the inorganic sunscreen ingredients can absorb. Light with wavelengths less than nm is almost completely absorbed. Light with wavelengths greater than nm is not absorbed at all. Jot down notes in the spaces below. There are several demonstrations embedded in the PowerPoint presentation that you can do with your class.

There is a choice of activities in this lesson. Both possible activities center around animations illustrating the interaction between visible light and sunscreen particles or skin, but one activity has students generate animations while the other provides them for the students to analyze. The animation creation activity is a more robust project that pushes students to really probe the underlying mechanism, but if time constraints are an issue, the pre-made animations discussion engages students in many of the same issues.

Students use the dedicated ChemSense Animator to aid them in this task.

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This project takes two days, plus an extra day if students have not used the program before. The Scattering of Light by Suspended Clusters: Student Reading provides more details about this kind of interaction between light and matter. The Reflecting on the Guiding Questions Worksheet asks students to connect their learning from the activities in the lesson to the overall driving questions of the unit.

Have students start to work in teams of 2 or 3 to create the animations. Circulate throughout the classroom to help students. Students continue to work on their animations. Towards the second half of the class, encourage students to finish up their animations and start to think about how they will present the animations to the class. Have students work individually or in small groups to fill out the Reflecting on the Guiding Questions: Student Worksheet.

This is also a good opportunity for you to address any misconceptions or incorrect assumptions from students that you have identified in the unit up until now. Have students work in teams of 2 or 3 to view the animations and answer the questions on the worksheet. If few computers are available, use a single computer and projector to make it a whole class activity. Source: Original Image 4-T9 This leaf absorbs red and blue light but reflects green light 7 What determines which colors wavelengths of visible light are absorbed?

This is important to highlight repeatedly during this lesson as students tend to get confused with the UV light interaction they have already studied. The slides begin with a brief introduction to the concept of color and its relationship to light as an electromagnetic wave. This foundation is then used to explain why our skin has the color it does and how large inorganic sunscreen ingredients interact with light to produce a white appearance.

Finally the slides discuss nanoparticles and why they appear clear. There are several demonstrations embedded in this slide set that you may want to prepare ahead of time. Answer: Because the light absorbing clusters are suspended in another medium, a single layer application does not provide total protection. Slide 3: What makes sunscreens with traditional size inorganic clusters appear white? Question Slide Have your students brainstorm ideas about why sunscreens with traditional inorganic clusters might appear white.

Question Slide Have your students brainstorm ideas about what gives skin its color. Is it is the skin matter itself? Is it the light from the sun? Is it the interaction between them? Ask them how they could gather evidence to support their view. Slide 5: Remember the Electromagnetic Spectrum? Discussion Question: Does visible light have more or less energy than UV light? Discussion Question: What kind of visible light has the most energy? What kind has the least? What kind falls in the middle? Slide 6: Reflected Light Gives an Object its Color Color Demonstration: To do this demonstration you will need to make one or more colored flashlights by placing a color filter in front of a flashlight.

Demo 1: Shine a white flashlight on a green apple in a dark room — the apple appears green because all light red, orange, blue except for the green light is absorbed.


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Shine a red light on the apple and it will appear a dark grey because there is no green light to reflect and all the light is absorbed. You can do similar demos with any color light and oppositely colored object. This shows that when no color is reflected, object appear black black is the absence of color. Demo 2: Shine a red flashlight on a white piece of paper in a dark room — that part of the paper will appear red.


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Add a blue flashlight and a yellow one on top of the red one. The paper should look white again because all three parts of spectrum are being reflected. This shows that the appearance of white is the combination of all colors. Similarly, a prism can be used to separate the different parts of white light back into a rainbow.


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Question Slide Have your students brainstorm ideas about what might determine which colors wavelengths of visible light are absorbed by different object. Discussion Question: Are the energy level spacings for molecules that absorb visible light greater or smaller than in molecules that absorb UV light?

Answer: The specific electron transitions caused by the absorption of visible light require less energy than UV transitions because visible light has less energy than UV. Biology Connection: The light energy absorbed by the chlorophyll is used in photosynthesis to make ATP. The electron transport chain is a series of rapid transfers between protein complexes and simple organic molecules oxidation-reduction reactions found in the membrane systems of the chloroplast.

This series of reactions produces energy rich molecules such as ATP. If they generate the idea that there is something in our skin that absorbs selectively in the visible spectrum, push them to think about whether it is the kind of these molecules or the quantity of them that accounts for different skin colors. Different melanin molecules absorb different wavelengths of light based on the differences in the spacing of their energy levels.

If you have covered Lesson 3 with your 4-T21 students, you can point out that melanin is an organic molecule and thus absorbs a small range of frequencies, similar to these molecules. The difference is that the spacing between the energy levels in melanin is smaller than for organic sunscreen molecules. Thus it absorbs visible light, which has less energy than UV light.

Slide So what makes sunscreens with traditional inorganic clusters appear white? Question Slide Have your students brainstorm ideas about what makes sunscreens with traditional inorganic clusters appear white. Possible Student Misconception 1: Students make think that sunscreen clusters absorb all colors of visible light, but if this were true, then the sunscreen would appear black. If students come up with this idea, you may want to review the demos in slide 6 with them. Possible Student Misconception 2: Students make think that sunscreen clusters reflect all colors of visible light.

Slide Inorganic Clusters Can Scatter Visible Light Scattering is a physical process that depends on cluster size, the index of refraction of the cluster substance and the index of refraction of the suspension medium. No energy transformations occur during scattering like they do in absorption , energy is simply redirected in multiple directions.

The size of the molecule or cluster is not important. Scattering is a physical process that does not involve an energy transformation. What light can be scattered is determined primarily by the size of suspended cluster, not its identity. Slide Multiple Scattering Light scattering is a common phenomenon that many of your students will have experienced though they may not realize that it…. You can show this to students by clapping blackboard erasers or shaking out any other kind of dust near a window on a sunny day.

Place the beakers on a dark tabletop and turn off the lights. Shine a thin 4-T22 flashlight or laser pointer through the side of the water container and have students look at the sides of the container. Then do the same for the beaker with the milk in it. For the milk and water beaker: You should be able to see the beam in the liquid since the proteins and other very small clusters in the milk are suspended in the water and scatter the light. To verify that light is scattered in all directions you can have your students try different observation points looking down on the beaker, looking at the beaker from an oblique angle.

Slide Front and Back Scattering Multiple scattering is a phenomenon of colloids suspended clusters. Light that has been absorbed cannot be scattered. If you are not planning on doing the animation activities with your class, you may want to demo the animations at this point.

Slide What do you think might be different about how sunscreen ingredients interact with visible light? Question Slide Have your students brainstorm ideas about what how nano sunscreen ingredients are different from traditional inorganic sunscreens ingredients they are much smaller and how this might influence the way they interact with visible light their size is much smaller than half the wavelength of visible light, thus they are not good scatterers for this kind of light.

While this may or may not change the amount of overall scattering, it reduces the amount of scattering in the visible range, which is what is important in determine appearance. Slide Nano ZnO and TiO2 Advanced Content: In addition to the problem of manufacturing nanoparticles of ZnO and TiO2, there is an additional problem in keeping the clusters dispersed since the clusters often tend to clump together.

This creates two problems: one, when clusters clump, the absorption of UV light can be spotty; and two, the effective cluster size becomes larger and the clusters are more likely to scatter visible light and appear white. You may want to talk with your students about the difference between primary cluster size and the dispersion cluster size. The difference is that even if you produce clusters of 15 nm, very often some of these will clump together in the sunscreen to form effectively larger clusters called dispersion clusters.

This is one reason that sunscreen manufacturers are so concerned with both the medium and the procedure for dispersing the clusters in the sunscreen formulation. For example, in the graphic shown for the 15 nm clusters the dispersion cluster size is nm and for the 35 nm clusters it is nm. Answer: No, decreasing the cluster size will not affect its ability to block the UV rays, because absorption is a chemical process and determined by the energy levels of the matter which do not change dramatically with size. Thus the nano-sized clusters are still good UV blockers.

Student Challenge Question: Why was the scattering issue never a problem for organic ingredients? Answer: Organic sunscreen molecules are smaller than 10 nm usually Angstroms and thus do not scatter in the visible range. Scattering causes all colors of visible light to be reflected back scattered to our eyes. The combination of all colors of visible light appears white, hence the sunscreen appears white. The process of making the many design decisions needed to create the animations will stimulate your students to consider the absorption and scattering processes in depth.

Having them work in groups will enhance the activity since they will need to discuss and reconcile their different conceptions of the process. Even if your students have seen scattering animations before, the process of making one will give them the opportunity to integrate and solidify their understanding of the process. Important: It is very important to review student animations with the whole class at the end of the project so that any parts of the animations that represent the phenomenon incorrectly can be identified and student misconceptions can be corrected.

Student will also get to see how the same phenomenon can be represented in multiple ways. Note: Your students should not have access to an existing scattering animation while they create their own, since this will cause them to replicate existing features without making their own design decisions. Sunsol, the prominent sunscreen maker, has just decided to launch a new product into the market.

The sunscreen will use a zinc oxide ZnO nanopowder as its only active ingredient, and will be formulated to go on clear and non-greasy. Sunsol is very excited about its new product, and wants to launch a full ad campaign to promote it to consumers who may not be familiar with the idea of a clear sunscreen that offers full spectrum protection. For this reason, they have decided that the ad campaign should center on an animated commercial that shows how traditional ZnO and ZnO nanopowders interact with UV and visible light.

Sunsol has invited several creative teams——including yours——to use the ChemSense Animator to create animations showing how the different sized ZnO particles suspended in the sunscreen will scatter visible light differently. The Request Sunsol is requesting a total of 4 animations: 1. Your teacher will put you in teams and let you know which of the animations you should work on. Note: Groups of students work well for this assignment.

Easy All UV light is absorbed 2. Easy All UV light is absorbed 4. Medium All visible light is scattered, skin appears white If time allows, you may want to assign groups to work on both the UV and visible animations for a given size particle e. In creating them, your students will have made tradeoffs between realism, simplicity, precision and generality.

It is important to have your students share their animations and discuss the advantages and limitations of each model as well as aspects that are inaccurately depicted so that they do not develop misconceptions about scattering. What aspects of scattering does it show particularly well? What aspects of scattering are not shown well? How do they show things in similar ways? Are different animations better at showing different aspects of the phenomenon?

Models which best align with or represent the empirical data we have are better. Apprentice 2 Partially developed Skilled 3 Adequately developed Masterful 4 Fully developed 3 - 4 of the required elements are present. All 7 required elements are present. Few of the required elements are accurately depicted. Some of the required elements are accurately depicted.

Most of the required elements are accurately depicted. All of the required elements are accurately depicted. Few or no key aspects of the interaction are correctly shown. Some aspects Most key All key of the aspects of the aspects of the interaction interaction interaction are correctly are correctly are correctly shown. Few or no key aspects of the blocking mechanism are correctly shown. Some key Most key All key aspects of the aspects of the aspects of the blocking blocking blocking mechanism mechanism mechanism are correctly are correctly are correctly shown.

Few team members contributed to the project. Some team members contributed to the project. Most team members contributed to the project. All team members contributed to the project. Group did not address the problems encountered. Group did not manage problems effectively. Problems in the group managed by one or two individuals. Group worked together to solve problems.

If you have a limited amount of in-class time you may want to do it as a whole class activity or assign it for homework if all your students have access to the internet with a follow-up class discussion. Important: These models are meant to provoke questions and start a discussion about how the scattering mechanism works as well as about the process of making decisions about how to represent things in models. Introduction There are many factors that people take into account when choosing which sunscreen to use and how much to apply. Two of the most important factors that people consider are the ability to block UV and the visual appearance of the sunscreen due to the interaction with visible light.

Then choose the sunscreen option and wavelength s of light as indicated to answer the following questions. Questions 3 — 7 look at the effects of the visible rays. Question 10 asks students to consider the tradeoffs, strengths and limitations of the animations as a model of the interaction of light and sunscreens. What happens to the skin when the UV light reaches it? The skin is damaged. The UVB light causes more immediate damage to the first cells it encounters because it is high energy. The UVA light is lower in energy and can penetrate deeper into the skin before it does damage.

What kind of sunscreen ingredients are shown in each animations? The 30 nm ZnO is a nanosized inorganic ingredient. The nm ZnO sunscreen is a traditional inorganic ingredient. What happens to the UV light in the animation of 30 nm ZnO particle sunscreen? The UV light is completely blocked via absorption. What happens to the UV light in the animation of nm ZnO particle sunscreen? Explain why this is so based on your understanding of how the sunscreens work to block UV light. There is no difference in how the 30 nm and nm ZnO particles interact with the UV light. Is there any difference in how the two kinds of UV light interact with the sunscreens?

Students may point out that wavelengths of nm are UVA light that might not be absorbed. This is true and can be discussed at part of the final questions which address the limitations of using models. Select the visible light option and play the animation for each of the sunscreen conditions. What happens to the visible light in each animation and what does the observer see? Skin without any sunscreen The photons of light pass through the air to the skin.

The observer sees the surface of the skin. Different skin colors are caused by different amounts and types of the skin pigment melanin. Skin with nm ZnO particles sunscreen 4-T33 The photons of light pass through the air and are refracted bent as they enter the sunscreen. They are then scattered by the ZnO particles multiple times until they emerge from the sunscreen and are again refracted bent.

Since large particles of ZnO scatter all wavelengths of light equally, all of the different photon wavelengths reach the observer who sees an opaque white surface. Note that even though the animation shows the different colored photons reaching the observer at different times, in reality there are many photons of each color reaching the observer at the same time.

Skin with 30 nm ZnO particle sunscreen The photons of light pass through the air and are refracted bent as they enter the sunscreen. What determines what the observer sees? Do they see the skin or the sunscreen? What color do they see? You see whatever substance the light touched last before it reaches your eye. The color is determined by which wavelengths of light are absorbed and which are reflected or scattered. How does scattering affect what the observer sees?

Since the pigments in the skin absorb blue-green light, skin generally has a reddish color. When the light scatters in the nm ZnO animation , the light reaching the observers eyes is reflected off of the ZnO particles so this is what they see. Since the ZnO scatters and thus reflects all wavelengths of light equally, it appears white. What variable determines if the visible light scatters or not?

For particles much smaller than this e.

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What would happen if we applied the large particle sunscreen in a layer only half as thick as the one shown? How would this affect its appearance? How would it affect its UV blocking ability? Appearance: There will be less ZnO particles to scatter the light and so some of the photons will reach the skin layer.

The sunscreen would not appear fully white but semitransparent you would see the skin but it would have a whitish color. What would happen if the observer eye moved 3 steps to the left to look at the skin? Only 5 photons are shown in each animation, but in reality there are many more photons involved both entering and leaving the sunscreen at different angles.

Thus there are many photons that never reach the eye of the specific observer shown in the animations. When we make a model such as these animations we make tradeoffs between depicting the phenomenon as accurately as possible and simplifying it to show the key principles involved. Are the different elements of the animation drawn on the same size scale? Which elements in the animation are really on or close to the nanoscale? Which are on the macroscale? Which are on the cosmic scale?

What are some other ways these animations have simplified the model of the real world situation they describe? How else could this be shown in the animations? What are some of the benefits of making a simplified model? What are some of the drawbacks? Benefits: Easier to see the core of what is going on for particular aspects of the phenomenon; can highlight one particular aspect you want to focus on. There is a tradeoff between realism, precision and generality.

What I learned in this activity: Possible Answers: It is also important to choose a sunscreen that we like in terms of appearance to make sure that we use enough of it to be effective. What I still want to know: 4-T37 2. When clusters are suspended in another medium like active sunscreen ingredients in the sunscreen lotion they can scatter light. Light is maximally scattered when its wavelength is twice the diameter of the cluster, so these clusters scatter significantly in the visible range. Some of the scattered light is back-scattered reflected back towards our eyes.

Since this light is of all visible colors, it combines to appear white. ZnO and TiO2 nanoparticles are much small in size with clusters of 3. Nano clusters are made up of the same kinds of atoms and have the same formula unit and the larger inorganic clusters, thus they absorb the same kinds of UV light: all wavelengths less than nm ZnO or nm TiO2.

Scattering is a phenomenon in which light is redirected in different directions by small clusters of atoms suspended in some other substance. A common example of scattering is when you shake out a dusty object in a sunny room - the dust seems to sparkle in the air. This effect occurs because the dust is scattering the sunlight, which then reaches your eyes. Scattering also explains why snow and salt are white, and why the sky is blue.

In each of these situations, the light is being redirected many times before it reaches our eyes. This is why the process is called multiple scattering. Figure 2: What is wrong with this picture? Try shining a flashlight at a wall in a dark room. Can you see the beam of light between the wall and the flashlight like in the picture above? Now sprinkle some baby powder in the air while you shine the beam. Can you see the beam now? When lots of clusters of one material are suspended in another material for example drops of water in the air, or active sunscreen ingredients in the lotion light has a chance to interact with these many clusters.

The interaction bends the light in many different directions. After this, it will then continue traveling in the suspension medium until it reaches another cluster. If the light is bent multiple times in multiple directions, we call this multiple scattering. Figure 3: Scattering of light by a suspended cluster Figure 4: Multiple scattering of light by suspended cluster While on the micro-level scattering redirects the light in many different directions, on the macro-level this combines to produce one of two results: the light is sent back in the general direction from which it came at various angles back scattering or the light continues in the same general direction it was moving, but at various angles front scattering.

Does Scattering Always Happen? Whether or not scattering will occur depends on many factors. For clusters suspended in a medium some of the most important factors are: the identity of the clusters, the identity of the suspending medium and the cluster size. Scattering happens most when the clusters have a diameter that is half as big as the wavelength of light involved. So a nm cluster would scatter nm light the most and it would scatter nm light quite a bit as well.

The amount of scattering continues to decrease as wavelengths become much bigger or much smaller than nm, as shown in figure 5. Interactions of light rays with ZnO particles and skin where appropriate correctly shown Few or no key aspects of the interaction are correctly shown. All relevant blocking mechanisms correctly shown Few or no key aspects of the blocking mechanism are correctly shown.

Teamwork Few team members contributed to the project. Interactions of light rays with ZnO particles and skin when appropriate correctly shown Few or no key aspects of the interaction are correctly shown. Two of the most important factors that people consider ate the ability to block UV and the visual appearance of the sunscreen due to the interaction with visible light. Questions 1. Explain why this is so based on your understanding of how the sunscreens work to block UV light 4-S11 3. Skin without any sunscreen b.

Skin with nm ZnO particles sunscreen c. Skin with 30 nm ZnO particle sunscreen 4. It includes a teacher grading rubric and peer feedback forms. Students also are asked to identify how their ideas have changed and what things if any they are still unsure about. These can serve as final discussion points or ideas for future investigation. Circulate through the room answering questions and probing student work. Day 2 50 min 10 min Hand out the Consumer Choice Project: Student Instructions and walk through the assignment and grading criteria with students.

Assign or let students pick the groups or 3 or 4 that they will work in. Hand back the corrected quizzes and go over the answers with students. Day 2 15 min 25 min Hand out the quiz and have students work on it on their own. Consumers have been contacting them lately to ask them if these new products are better than traditional sunscreens, if they are safe to use, and how to know if a sunscreen uses nanoparticulate ingredients.

To help consumers decide whether these products are right for them, SmartShopper has decided to produce a pamphlet that tells consumers all they need to know about these new products.

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SmartShopper also will need to take a position on whether or not they endorse the use of the sunscreens and justify this position based on a comparison of the benefits and risks backed up with science. They turn to you and your team to create this pamphlet. Requirements SmartShopper asks that your pamphlet makes full use of both sides of an 8. Nanoparticulate sunscreen ingredients are inorganic UV blockers. This means that they are made out of the same atoms and have an ion lattice structure like standard inorganic sunscreen ingredients, but the particle size the number of atoms that group together is much smaller.

They are different from organic UV blockers which are usually conjugated carbon compounds and exist as discrete molecules i. You can also look at the actual color of applied sunscreen to see if it is the nano-version. Sunscreens with nanoparticulate ingredients block UV rays by absorbing them. The opacity of a material depends on the degree to which it scatters light.

Nanoparticles are so much smaller than the wavelength of visible light that they do not scatter it effectively. When the receptors in our eyes received by the reflected rays we they produce the image of our skin that we see. Students do not need to create this graph themselves — they can use a graph from the unit materials or find one online. The process of absorption excites an electron giving it energy that can lead to side reactions. Some of these side reactions can create to free radicals particles known to contribute to cancer or damage DNA.

In addition, because nanoparticles are so small, it may be easier for them to penetrate and circulate throughout the body. The biggest issue with nanoparticulate ingredients is not that they are necessarily more dangerous than other ingredients but that because they are new, they have not been fully researched yet. By Hand: Take a regular piece of 8. Fold the paper into thirds and crease it firmly.

When you unfold the paper, you can use the creases as column guides. It is good to make the front and back of your pamphlet on different pieces of paper and use a copying machine to make the pamphlet double sided in case you decide to make changes along the way. With a Computer: Open a new document in Microsoft Word. You will need to either use a printer that will print double-sided or print the two sides of your pamphlet separately and use a copying machine to make them double sided.

Visible opacity, 2. UVA blocking and 3. UVB blocking. All 8 parts of the required information are present. Few of the claims are backed up. Some of the claims are backed up. Most of the claims are backed up. All of the claims are backed up. All 4 key aspects of the interaction are correctly shown. All 4 key aspects of the argument are given effectively. Why is UV light a source of health concern when visible and infrared light are not?

List 2 kinds of damage to the body caused by UV radiation. Explain in your own words why it is important to block UVA light. How do you know if a sunscreen protects against UVA light now and future?

How do you know if a sunscreen protects against UVB light? For each of the following absorption graphs, circle the correct answers for a what kind s of light are strongly absorbed and b whether it is an organic or inorganic sunscreen. Why do sunscreens that use nano-sized TiO2 clusters appear clear on our skin while sunscreens that use traditional sized TiO2 clusters appear white? Thus our skin color is what we see, making the nano-sized TiO2 particles effectively clear. The specific absorption mechanism is different, but students are not expected to report this Similar or Different How: Both nano and organic ingredients appear clear on the skin.

Now that you have come to the end of the unit, go back and look at the reflection forms you filled out after each activity and try to answer the guiding questions below. Write down answers each question below and then evaluate how confident you feel that each idea is true. The goal of this exercise is for students to reflect on their learning and evaluate how their ideas and their confidence in them has changed since the unit began.

The answers to the questions on page two are also a final check for you to see where students are and if they have any misconceptions that need to be addressed. Possible student answers are listed below, these are compiled based on completion of the entire unit. If you have only done selected lessons with your class, some of the answers many not apply. Most ingredients currently used in sunscreens are organic ingredients. Not So Sure How sure are you that this is true? What things are you still unsure about? What ideas are different and how? What ideas do you have now that are the same as when you started?

Then answer the following questions. What are the name s of the student team who developed the pamphlet you are evaluating? Is all of the required information present and correct?