Photosynthesis Check-In

Formative Assessment · 8th Grade Science
Standard: NGSS MS-LS1-6

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About this check-in

What this checks (NGSS MS-LS1-6): Can you explain, using evidence, how photosynthesis moves matter (atoms) and energy into and out of living things?

How it works: Part A covers the core ideas. Part B asks you to stretch and explain your thinking. Do your best on every question — this helps your teacher see what to review. It is not graded for points.

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Part A — Core Ideas

Level 1 — the building blocks

1. What two things does a plant take IN from its surroundings to carry out photosynthesis?

A. Oxygen and sugar

B. Carbon dioxide and water

C. Sugar and soil

D. Nitrogen and salt

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2. Where does a plant get the energy it needs to run photosynthesis?

A. From minerals in the soil

B. From sunlight

C. From the oxygen in the air

D. From the water it drinks

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3. Photosynthesis makes a sugar the plant can use as stored food. Which molecule is that?

A. Carbon dioxide (CO2)

B. Water (H2O)

C. Glucose, a sugar (C6H12O6)

D. Oxygen (O2)

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4. True or False: “A plant gets most of the material it uses to grow from the soil.” Circle one: TRUE / FALSE

Then explain your choice in one sentence.

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5. Fill in the blanks to complete the word equation for photosynthesis:

______+ ______ —(light energy)→ ______ + ______

Hint: Two things go in, two things come out.

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Part B — Stretch Your Thinking

Level 2 — explain with evidence

6. A plant absorbs light energy from the Sun. That energy does not disappear — it changes form. Where does the light energy go? Describe what it becomes.

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7. A student says: “The carbon atoms in the sugar a plant makes come from the sunlight.” Is the student correct? Explain where the carbon atoms actually come from.

Hint: Sunlight is energy. Atoms are matter. Are those the same thing?

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8. A plant is sealed in a clear container in bright light. Over a few hours, the CO2 in the container goes down and the O2 goes up. What does this evidence tell you the plant is doing? Explain how you know.

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9. Claim: “Photosynthesis moves both matter and energy.” Support this claim with evidence in 2–3 sentences. (This is the big idea of the whole unit!)

Sentence starters: “Matter moves because…” “Energy moves because…”

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10. Explain how the oxygen you breathe is connected to photosynthesis. In your answer, describe matter moving from one place to another.

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Answer key and teacher notes

For open-response items, accept any answer that shows the key reasoning below — exact wording will vary. Bracketed tags show what each item reveals about student understanding.

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1. B — Carbon dioxide and water [Identifies inputs / matter taken in]

These are the two inputs (reactants) the plant takes in. A, C, and D include products or unrelated substances.

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2. B — From sunlight [Distinguishes energy source from matter]

Light is the energy source. Soil minerals and water are matter, not the energy that drives the reaction.

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3. C — Glucose, a sugar (C6H12O6) [Identifies the energy-storing product]

Glucose is the food molecule that stores chemical energy. Oxygen is also a product but is not the plant’s stored food.

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4. FALSE [Matter: source of plant mass]

Most of a plant’s mass comes from carbon dioxide in the air — the carbon atoms in CO2 become part of the sugar and plant body — plus water, not from soil. Soil mainly provides water and small amounts of minerals. This targets a very common misconception.

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5. carbon dioxide + water → sugar (glucose) + oxygen [Reactants and products of photosynthesis]

Accept CO2 + H2O → C6H12O6 + O2. Inputs may be in either order; same for products.

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6. Light energy is transformed, not lost [Energy flow and transformation]

The light energy is captured and stored as chemical energy in the bonds of the sugar (glucose) molecules the plant makes. It changes form — light to chemical — rather than disappearing.

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7. Student is incorrect [Energy vs. matter; source of carbon]

Sunlight provides energy, not atoms. The carbon atoms come from carbon dioxide (CO2) gas the plant takes in from the air. Full credit distinguishes energy (from the Sun) from matter (carbon from CO2).

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8. The plant is doing photosynthesis [Interprets evidence / data]

Falling CO2 shows the plant is using up a reactant (taking in matter); rising O2 shows it is producing a product and releasing it. Together that is evidence of photosynthesis.

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9. Claim supported by matter AND energy [Constructs evidence-based explanation — anchor item]

Matter: atoms from CO2 and water are rearranged into sugar and oxygen — the atoms are conserved, just reorganized. Energy: light energy from the Sun is captured and stored as chemical energy in the sugar. A strong answer addresses both matter and energy with evidence. This item is the core of MS-LS1-6.

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10. Our oxygen is a product of photosynthesis [Matter cycling across organisms / systems]

Plants release O2 as they make sugar. Those oxygen atoms move out of the plant into the air, and animals (including us) take them in when we breathe. This shows matter cycling between plants and animals.

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Quick formative read

• Part A mostly correct: student has the core inputs and outputs — ready for Part B reasoning.
• Misses #4 or #7: revisit “where plant mass comes from” and the energy-vs-matter distinction.
• Weak on #9: reteach how photosynthesis connects matter cycling and energy flow — the MS-LS1-6 target.

Fraction Multiplication

Three common misconceptions in Grade 5 — and questions to surface them

Subject: Mathematics · Grade 5

Topic: Multiplying fractions

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Overview

Fifth graders bring three big misconceptions into fraction multiplication, and each one comes from over-applying rules that worked for whole numbers. The diagnostic questions below are designed to bring each faulty mental model into the open during discussion.

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1. "Multiplying always makes things bigger."

Years of whole-number multiplication teach kids that products are larger than the factors, so ½ × 8 = 4 feels wrong to them — like it should have been division.

• "I multiplied two numbers and my answer was smaller than one of them. Did I do something wrong? Why or why not?"
• "Without calculating, will ¾ × 20 be more than 20 or less than 20? How do you know?"
• "When does multiplying make a number bigger, when does it make it smaller, and when does it keep it the same?"

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2. "You need common denominators to multiply."

Rules from addition leak over. Students who just learned to find common denominators for adding fractions often insist on doing it for multiplication too — or, conversely, they add straight across because multiplying straight across worked.

• "Jayla says you have to change ⅔ × ¼ into twelfths before you can multiply. Marcus says you can just multiply across.”

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3. "× means groups of whole things."

Kids don't yet understand that ⅓ × ½ means "a third of a half." They can execute the multiply-across algorithm without any idea what the answer represents, which is why they can't estimate or check whether an answer is reasonable.

• "What does ½ × ⅓ mean in words? Can you tell a story problem that matches it?"
• "Shade ⅓ of a rectangle. Now shade ½ of that piece. What fraction of the whole rectangle did you shade, and how does that connect to the numbers?"
• "Why is ⅓ of ½ the same as ½ of ⅓? Convince a skeptic with a drawing, not just the algorithm."

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A thread across all three

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Keep asking students to predict the size of the answer before computing.

That single habit surfaces every one of these misconceptions in discussion, because the wrong predictions come straight from the faulty mental models.