chemistry pogil activity «activity_» lesso… · web viewin model 5, the little green oval...

8th Grade Science POGIL Activity Topic: Photosynthesis

Photosynthesis – From Light to FoodWhy? Plants don’t eat food like you do. In this activity we will address the question:

How do plants get energy?

Group Instructions: When responding to each question, one group member should be assigned the task of reading the question aloud for the rest of the group. Rotate the reading among the group members throughout the assignment so that everyone gets several turns. Remember, allow everyone the chance to respond, and respect each other’s ideas, feelings, and answers.

Model 1

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1. Name two living (biotic) organisms you see clearly in Model 1.A deer and flowers.

2. Explain how each organism in Model 1 gets the energy it needs to live.a. The deer gets energy by…eating the flowers.

b. The flowers get energy from…changing sunlight into food for themselves.

3. The flowers are ____ producers ___ and the deer is a ____ consumer ___. producers/consumers producer/consumer

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8 th Grade Science POGIL Activity Photosynthesis & Cellular Respiration – How do cells get and use energy?

Look at and discuss Model 2. Label the PRODUCERS and CONSUMERS in the picture.

Model 2

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Compare and contrast the terms producers and consumers by listing at least 2 things they have in common and at least 2 things they don’t have in common.

4. PRODUCERS CONSUMERS

Make their own food from sunlight. Get their food from eating other organisms.

Autotrophs Heterotrophs

Ex: plants, algae, & some bacteria Ex: herbivores, omnivores, carnivores.

5. Do you think that the deer only uses the energy that is made by the plant using sunlight? Explain.

Answers will vary. By the end of the lesson students should explain that although the energy from the plants can be used to fuel the deer when it eats them, the purpose of photosynthesis is for the plant to make food for itself.

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PRODUCERS

CONSUMERS



6. Is there anything beneficial, other than food that the plant is providing to help the deer to breathe?

Oxygen

7. Do you think that the food and oxygen the plant is making from the sunlight were made on purpose for the deer or for something or someone else? Explain.

Answers will vary. By the end of the lesson students should explain that although the energy from the plants can be used to fuel the deer when it eats them, and the oxygen the plants make help the deer breathe, the purpose of photosynthesis is for the plant to make food for itself and the some of the oxygen the plant makes also is used by the plant to help break down the food as well.

8. What is the name given to the process whereby plants use sunlight to make food?

Photosynthesis

9. What steps do you think are involved in photosynthesis?

Step 1: Sunlight reaches the leaves of a plant.Step 2: Carbon dioxide enters the bottom of the leaves through the stomata.Step 3: Water enters the roots and travels around the rest of the plant.Step 4: The sunlight is captured by the chloroplasts and converted into food (glucose) for the plant.Step 5: Oxygen is released as a by-product back out through the stomata

Think of a time when you may have helped your mother or someone else bake a cake and discuss with your group what important pieces of information are needed before starting to make a cake. [NOTE: When you are at this point, ask your teacher to show you an example of cake recipe and have your group examine the back of a box a cake mix.]

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10. A recipe is a set of instructions needed to make a food dish along with a list of ingredients needed to make it. Do you think it’s important for the recipe to include how much of each ingredient you need? Why or why not?

Yes, because if you don’t know how much of each ingredient to use the food won’t come out right.3




11. Once you mix all of the ingredients according to the recipe instructions, what still has to be done to the mixture to make it look like a cake?

The cake batter still has to be cooked to bake the cake.

12. Did it take energy to mix all of the ingredients together? If so, where did that energy come from?

Yes, from the muscles in my arms and hands. Or, if using an electric mixer, from electricity and mechanical energy.

13. Did it take energy to bake the cake? If so, where did that energy come from?

Yes, from the electricity powering the oven.

14. Does it take energy to eat the cake? If so, where did that energy come from?

Yes, it takes chemical energy and mechanical energy to chew and break down the food. It takes more chemical energy in digestion to break the food down further into nutrients cells can use.

Reactants are the materials you use to make something new. The reactants often change into something else once they are combined and many times don’t look the same as they did before. Products are the materials that are made as a result of combining the reactants.

15. Think back to our cake example. What are some of the materials (reactants) needed to make the cake? What product or products were made at the end?

REACTANTS PRODUCTS

Flour, eggs, baking soda, salt, The cake and gases that made the cake rise. Some students might recognize that some energy was lost as heat energy as well.




PHOTOSYNTHESIS

Believe it or not photosynthesis helps keeps you alive. It is one of the most important processes on Earth! Humans and plants are dependent on each other for survival. Can you figure out what photosynthesis means just by reviewing its word parts? The prefix photo means “light” and the synthesis means “putting together.”

16. Write your own definition for the word photosynthesis below.

Answers will vary. Students might respond: Photosynthesis puts together food from light.

But did you know that plants don’t make food for us to eat, but they use sunlight to make food for themselves? Even though humans and other organisms eat plants for energy, that is not who they are making the food for. Plants need to eat, too, to say alive. So, you could say that the process of photosynthesis is like a plant cooking for itself. Many creatures just happen to like to eat plants and take some of the energy as well. What’s even more wonderful, than plants providing us with yummy food fuel, is that through photosynthesis, plants also provide us with oxygen, which we can’t live without. Again, plants don’t make it on purpose just for us to breathe; it just happens to be what is made as a result of combining the reactants together. Scientists call this a by-product. It’s kind of like when you burn a piece of paper with a match and ash and smoke form which are both by-products. Oxygen just resulted from the chemical change. The plant will use some of it to help break down glucose when it’s ready to eat, very much like when we digest food. The process of breaking down food by plants and animals will be dealt with in a future unit.

Model 3 is shows you the recipe for photosynthesis along with a list of the ingredients and their amounts. This is the way scientists write recipes except they call them chemical equations instead. The top row shows you the chemical symbols for each ingredient while the bottom row shows you the common name for them. Study and discuss Model 2 in your groups now.

Model 3

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17. List the reactants and products from Model 3 in the table below.

REACTANTS PRODUCTS

Carbon dioxide, water, and light Sugar (glucose) and oxygen5




18. Can you find the ingredient that doesn’t include how much of it to use? Why do you think that is?

Light. Students might say because you can’t measure how much light is made and that possible different amounts of light are used depending on the weather.

19. Is light a reactant or product? Explain your answer.

A reactant because light is what the leaves need to start making food.

20. What do you think the big arrow pointing to the right in between Water and Glucose means in Model 3?

The arrow means that the reactants are making the products and not the products coming together to make the reactants. The equation only goes in one direction.

21. Think of our cake example. Can we turn our finished baked cake back into the original ingredients? Once photosynthesis occurs, do you think it can be undone?

No, the cake can’t return back to the eggs, flour, and other original ingredients. No, photosynthesis can’t get the sunlight and carbon dioxide back from the oxygen and glucose that was made.

22. Remember the deer in Model 1? Using the chemical formula, which product does the deer use to breathe?

Oxygen

23. Which product does the deer use for energy?

Glucose (sugar)

24. Which by-product do deer, humans, and many living organisms use to breathe?

Oxygen

ENERGY TRANSFER AND ENERGY TRANFORMATION

Recall that energy is the ability to do work and there are several types of energy. Living organisms need energy to perform all their life functions. Larger organisms require more energy than smaller organisms. Eating, breathing, talking, thinking, digesting, moving, even sleeping requires energy. Mixing the cake batter required mechanical energy from the muscles in your arms and hands. Baking the cake took heat energy from the oven.

Also, remember that energy can never be created or destroyed only transferred (sent somewhere else) or transformed (changed into another form). For example, a car runs on fuel (gas). The liquid gas doesn’t stay in the tank forever. It eventually runs out. But we just said energy can never be destroyed so what



8 th Grade Science POGIL Activity Photosynthesis & Cellular Respiration – How do cells get and use energy?happened to the liquid gas? When a car is turned on it makes a controlled mini-explosion and starts burning the gas. The chemical energy in the gas is being transformed into mechanical energy so the car moves where you want it to go. Some heat energy is released as well as the car gets warm the more we use it. Unfortunately, after the gas burns, carbon dioxide is sent up into the air and is bad for our environment as. Chemical energy is also stored in food. It’s transformed after we eat it into mechanical energy so we are able to do all of the things we want to do. Even we get warm the more we move so some of the food energy we digest transforms into heat energy, too. Sometimes after we eat we send gases into the air, too, that aren’t bad for the environment but they aren’t always pleasant to smell.

Circle the best answer.

25. What kind of energy is the plant making for itself when it makes glucose? Circle the portion of the text (text evidence) above that helps you answer this question.

a. Light energyb. Chemical energyc. Sound energyd. Mechanical energy

Review the following chemical equation again in your groups.

26. What type of energy change is happening between the reactants and the products?

Energy transformation

27. Is light energy transferring into chemical energy or is transforming into chemical energy?

Tranforming because it’s changing into something new.

You’ve already learned that food can be broken up into 3 main groups: Carbohydrates, proteins, and fats. We eat carbohydrates for most of our chemical energy needs. Glucose is a carbohydrate, specifically a sugar carbohydrate. Plants use this sugar as its source of fuel and when we eat plants we are using them for fuel, too.

HOW DOES PHOTOSYNTHESIS WORK?



8 th Grade Science POGIL Activity Photosynthesis & Cellular Respiration – How do cells get and use energy?Model 4

Public Domain Image

Photosynthesis happens in the leaves of the plant. The leaves are a lot like solar catching solar panels. Sunlight isn’t enough though. Just like a cake requires more than flour, photosynthesis requires more ingredients. Water is taken up into the rest of the plant parts through the roots and carbon dioxide enters the bottom of the leaves through mouth-like structures called stomata.

CHLOROPLASTS

Have your group watch the Bill Nye the Science Guy video on chloroplasts to review what you learned back in 6th grade using this link: http://www.youtube.com/watch?v=dax7v711qg0.

Model 5

Public Domain Image

Inside the leaves the light is moving directly into the green chloroplasts where the sunlight will be transformed into chemical energy in the form of glucose. This glucose will be used as a source of



http://www.youtube.com/watch?v=dax7v711qg0

8 th Grade Science POGIL Activity Photosynthesis & Cellular Respiration – How do cells get and use energy?energy for the plant itself to perform all of its life functions such as reproduction, growth, and the making of more food.

In Model 5, the little green oval shaped organelles are the chloroplasts.

Circle the best answer.

28. In what part of the plant does most photosynthesis take place in?a. The rootsb. The flowersc. The stemd. The leaves

29. What structure in plant leaf cells does the light energy transform into glucose (chemical energy)?a. Cell wallb. Chloroplastsc. Nucleusd. Water vacuole

30. What part of the plant takes in carbon dioxide?

Stomata in the underside (bottom) of the leaves.

VIDEO OPPORTUNITYIn your groups, watch and discuss the video entitled, “The Simple Story of Photosynthesis and Food” only up to time marker 2:28 with the link http://www.youtube.com/watch?v=eo5XndJaz-Y.

HOMEWORKFor homework, go back and review your answers to every question. If you feel like you may have answered any questions incorrectly, add your new answers in red pen next to your old answer. DO NOT ERASE YOUR OLD ANSWERS. Then, summarize what you have learned in this lesson in a 1 page essay. On the back of your essay, draw and label what happens during photosynthesis.

EXTRA CREDIT 2In this lesson you learned that plants make food for themselves using sunlight through photosynthesis. What is the cell process called that breaks down that food into nutrients the cells can use to live and perform all of its functions? cellular respiration

EXTRA CREDIT 3Write an extended answer to the following questions. Why doesn’t a plant die at night when the Sun goes down? Does photosynthesis stop at night?

Yes, photosynthesis does not take place at night because photosynthesis requires sunlight and when it’s dark there isn’t any. Plants have not used all of the glucose it has made while the Sun was out so it has stored glucose to use for fuel when photosynthesis isn’t happening.



http://www.youtube.com/watch?v=eo5XndJaz-Y

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