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Cells and Systems 6-8 / Week 08 / Wednesday
3/6
Week 08 · Plants Make Food

Wednesday

Windowsill Lab: Dark paper and dark jars
// Light, air and water become sugar
⏱ about 20 min

Wednesday: Windowsill Lab: Dark Paper and Dark Jars

Rocket cuts nothing today. Instead he folds a square of dark paper around one leaf of the garden plant and clips it with a paper clip.

"One leaf in the dark," he says. "The rest in the light. Same plant, same water."

Raven lines up three clean jars on the Windowsill, each with a damp paper towel and three dried beans.

"Jar A on the sill. Jar B in the dark cupboard. Jar C stays on the sill but gets no water," she says.

"What do you notice we are changing?" she asks. "Only one thing per jar."

Nova hovers over the row. "Predict now, and read the jars in two weeks," she says. "A scientist waits."

Rocket writes three predictions and seals the Log shut with a rubber band so he cannot peek.

Your mission

Today you start two experiments that run longer than a day. Both test what light does for a plant.

First, you cover one leaf on a living plant with dark paper for one week. Then you compare it with its neighbors.

Second, you start three seed jars. One gets light and water, one gets water but no light, and one gets light but no water.

You will read the seed jars in week 10. Until then, you only keep the damp jars damp and write what you see.

  • A living garden plant or houseplant your family owns, with a grown-up's permission
  • A small square of dark paper or foil, and a paper clip
  • Three clean glass jars or clear plastic cups, labeled A, B and C
  • Paper towels, water, and nine dried beans or lentils from the pantry, handed over by a grown-up
  • A dark cupboard or a box with a lid, your Windowsill Log and a pencil
Safety first
Use only pantry beans or lentils a grown-up hands you. Never seeds from a garden packet, which may be treated.
Beans are lab materials, not snacks. Nothing is tasted or eaten. Wash your hands after every step.
Cover a leaf on a plant your family owns, with permission. Never an unknown plant. Do not pinch or bend the stem.
Jars stay on the sill, the table or the cupboard shelf. A grown-up handles any water that is not cool tap water.
  1. Choose one healthy leaf. Fold the dark paper over both sides so no light reaches it, and clip the paper gently at the edge.
  2. Write today's date in your Log. The paper stays on for seven days.
  3. Fold a paper towel to fit each jar. Wet the towels for jars A and B with cool tap water until damp, not dripping.
  4. Leave the towel for jar C dry. Put three beans against the glass in each jar, halfway up, so you can see them.
  5. Set jars A and C on the sunny sill. Put jar B in the dark cupboard or under the box.
  6. Every two days, add a little water to A and B if the towel feels dry. Never water C.
  7. Each time you check, write one line per jar in your Log. Do not move the beans.
SetupLight?Water?My predictionWhat I see today
Covered leafnoyes (same plant)
Jar Ayesyes
Jar Bnoyes
Jar Cyesno
PREDICT BEFORE YOU WAIT
  • Read the question.
  • Tap your answer.
Which jar is the fair comparison, with everything a bean needs?
Jar B differs from jar A in only one way. What is it?
The covered leaf gets water from the plant but no light. Which starting reactant of photosynthesis is it missing?

Reading your setup

Photosynthesis requires sunlight, carbon dioxide and water. The covered leaf still has air and water but no light.

Chlorophyll absorbs light. Without light there is no energy to build sugar, no matter how much air and water arrive.

The seed jars test something a little different: what a sprouting bean needs to grow. Week 10 will read the answer.

A fair test changes one thing at a time. That is why jar B is dark but damp, and jar C is lit but dry.

Predictions are written before the result. A wrong prediction is good science if the method was fair.

What the setup showsTrue or false?
The covered leaf still gets water and air from the plant.?
Jar B and jar C differ from jar A in two ways each.?
A prediction is written before the result is known.?
Jar C should be watered when its towel feels dry.?
WHY THIS EXERCISEA fair test with one change per jar is what lets week 10 explain the results.
How many days does the dark paper stay on the leaf? Type a number.
WHY THIS EXERCISEKeeping to the planned time is part of the method, like the ten minutes before a pulse count.
Draw your three jars side by side with their labels, and the plant with one leaf wrapped in dark paper.

Careful setup. Tomorrow you will read NASA's description of the carbon cycle and follow a carbon atom around.

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