📚 Grade: Kindergarten⏱️ Duration: 30–45 minutes🌿 Subject: Life Science — Plants & Seeds🧰 Kit Lesson: No
☀️🌿 🆚 🌑🌿
Two plants. Same water. But only one gets sunlight — what do you think will happen?
📋 NGSS Standard: K-LS1-1 — Use observations to describe patterns of what plants and animals (including humans) need to survive.
🎯 Learning Objective
Students will observe what happens when a plant doesn't get sunlight and conclude that plants need light to survive.
🎯 The Big Idea
Plants are amazing — they make their own food! But to do that, they need sunlight. In this lesson, your kids will set up a simple experiment: one plant in a sunny spot, one in the dark. Over 3–5 days, they'll observe what happens and discover firsthand why sunlight is so important for plants.
🔬 The Science
Plants use sunlight, water, and air to make their own food — this process is called photosynthesis. It happens inside the green parts of a plant (the leaves!). When a plant doesn't get enough sunlight, it can't make food. It gets weak, pale, and stretched out — reaching desperately toward any light it can find.
A plant left in complete darkness will start to look very different from one in a sunny window: it turns pale yellow or white, grows tall and spindly (scientists call this etiolated), and eventually droops. It's not dead — but it's definitely not healthy.
Two small potted plants (roughly the same size) or use the bean sprouts from Lesson 2 if they've grown!
If using bean sprouts: pick two cups that look similar in size and health
🏠 Setup Supplies
A sunny windowsill or bright spot (Plant A)
A dark closet — or even better, a cardboard box with a lid (Plant B)
Water & a small cup for watering
Observation journal or a blank notebook
Pencil and crayons for drawing observations
🔬 Let's Get Started
Step 1 — Set Up the Experiment FIRST (5 min)
Before anything else, get the experiment going — it needs 3–5 days to work!
Label two plants (or cups): "Sunny" and "Dark"
Place the "Sunny" plant on the brightest windowsill you have
Put the "Dark" plant in a closet, or better yet, inside a cardboard box with the lid closed
Water both plants the same amount right now
Say: "We're going to let these plants sit for a few days and then see what happened. We're scientists making a prediction — what do you think will happen to the dark plant?"
Step 2 — Make a Prediction (5 min)
In their observation journal, kids draw both plants as they look right now (they should look the same!). Ask: "Draw what you think each plant will look like in 3 days. Will they be the same? Or different?"
Write or dictate their prediction underneath.
Step 3 — Talk About What Plants Need (10 min)
While the experiment runs, discuss! Use the questions below. Cover the key ideas:
Plants need water, air, and sunlight to survive
Sunlight gives plants the energy to make their food (photosynthesis!)
Without sunlight, a plant can't make food — and gets weak
Try this: turn off the lights in the room for a moment. Say: "Imagine living in the dark all the time — with no food. How would you feel? That's how the plant in the box feels!"
Step 4 — Daily Check-Ins (over 3–5 days)
Each day, take a quick peek at the sunny plant and open the box for the dark plant. Ask kids:
"Has anything changed?"
"What color is it? Is it standing up straight or drooping?"
Draw a quick sketch in the observation journal each day. Water both plants the same amount.
Step 5 — Big Reveal: Side-by-Side Comparison (in Lesson 5 or 6)
After 3–5 days, bring both plants out and put them next to each other. Let the kids look closely. Then complete the Student Worksheet: draw both plants side by side and circle which one looks healthier.
Step 6 — Wrap Up (5 min)
Ask: "So what do plants need that the dark plant wasn't getting?" Guide kids to say: SUNLIGHT!
Introduce the word photosynthesis: "Plants make their own food using sunlight — that's called photosynthesis. Pretty cool, right?"
💬 Discussion Questions
🗣️ Question 1: "The plant in the dark is still alive — but does it look healthy? What's different?"
💬 The dark plant looks pale and stretched out because it's reaching for light. Plants need sunlight to make their food through their leaves — that's photosynthesis. Without it, they get weak and can't stay healthy. They're still alive, but just barely hanging on!
🗣️ Question 2: "What would happen if all the clouds covered the sun for a whole year?"
💬 Without sunlight, plants couldn't make their food and would die. Without plants, animals that eat plants would lose their food. Even meat-eating animals would eventually run out of food too. Everything in nature is connected — sunlight is the very beginning of almost all food on Earth! (This is called a food chain — a fun look-ahead for later lessons.)
🚀 Extensions
🌀 Partial Light Test: Try a third plant — put it in a dim corner (not totally dark, not sunny). Where does it end up compared to the other two?
🌿 Leaf Rubbings: Place a leaf under paper and rub a crayon over it. Look at the veins — those carry water and sugars made by photosynthesis!
📚 Read Aloud:"A Seed Is Sleepy" by Dianna Hutts Aston or "From Seed to Plant" by Gail Gibbons
🎨 Color Sorting: Look at pictures of healthy plants (green, upright) and unhealthy plants (yellow, droopy). Sort them: "Enough sunlight" vs. "Not enough sunlight"
🔭 Grow Toward the Light: Put a plant near a window for a week and watch it lean toward the light. This is called phototropism — another bonus word for curious kids!
👩🏫 Parent/Teacher Notes
⚡ Start the experiment FIRST: Do Step 1 at the very beginning of the lesson — the experiment takes 3–5 days to show results. Final observations happen in Lesson 5 or 6, so plan accordingly.
📦 Box beats closet: A cardboard box with a lid works better than a closet — it's completely dark, stays the same temperature, and is easy for kids to peek inside without flooding the plant with light each time.
🫘 Lesson 2 connection: Check on the 3-cup experiment from Lesson 2 (seed, no water, no soil). Which cups have sprouted? Compare notes — seeds need water to germinate, but plants need sunlight to keep growing.
🔬 Introduce photosynthesis gently: Don't shy away from the big word! Say it a few times and make it fun: "Photo means light, and synthesis means making — so photosynthesis means making food with light!"
🌿 Fun bonus word: The pale, leggy, stretched-out look of a plant grown in the dark has a scientific name: etiolated. You don't need to teach it, but curious parents may enjoy knowing it!
✅ Assessment: Can the child explain that plants need sunlight to stay healthy? Can they point to the healthier plant and say why it looks better? That's the win.
After 3–5 days, draw what each plant looks like. Then answer the questions below!
☀️ Sunny Plant
This plant was on the windowsill
Draw here ✏️
🌑 Dark Plant
This plant was in the dark box
Draw here ✏️
🔍 What did you notice?
Write or tell one difference between the two plants:
Circle the plant that looks healthier:
☀️ Sunny Plant
or
🌑 Dark Plant
Why does the plant need sunlight? (write, draw, or dictate)
🌿 Big word I learned today:Photosynthesis
— plants make their own food using sunlight! ☀️🍃
📋 PARENT / TEACHER ANSWER KEY — Detach before giving worksheet to students
🌿 What to Look For After 3–5 Days
The Sunny Plant should look green, upright, and healthy — maybe even a little bigger
The Dark Plant will look pale (yellow or white), stretched tall and spindly, and possibly droopy or leaning
Both were watered equally — the only variable was sunlight
☀️ Why the Dark Plant Looks Different
Without sunlight, the plant cannot perform photosynthesis — the process by which it makes its own food using light energy. The plant stretches toward any available light source (a behavior called phototropism), causing it to grow tall and thin. It loses its green color (chlorophyll breaks down without sunlight) and becomes pale. The plant is alive, but weak and unable to thrive.
✅ Worksheet Expected Answers
One observed difference (any valid observation): "The dark plant is yellow," "The sunny plant is greener," "The dark plant is taller and droopy," "The sunny plant looks stronger"
Circle the healthier plant: ☀️ Sunny Plant
Why does the plant need sunlight: "To make food" / "To stay green and strong" / "So it can grow"
💬 Discussion Question Answers
Q1 — "The plant in the dark is still alive — but does it look healthy?"
Expected: No! The dark plant looks pale, stretched, and droopy. Plants need sunlight to make their food (photosynthesis), so without light they get weak even if they still have water.
Q2 — "What would happen if all the clouds covered the sun for a whole year?"
Expected: Plants would die without sunlight. Then animals that eat plants would lose their food. Eventually all living things would be affected. Sunlight is the energy source at the base of almost all food chains on Earth.
🔬 Vocabulary Check
Photosynthesis: The process plants use to make food from sunlight, water, and air
Sunlight / Energy: The source of power plants need to run photosynthesis
Survive: To stay alive and healthy; what plants (and animals!) are trying to do
Etiolated (bonus!): The scientific word for a pale, leggy plant grown without enough light
✅ What Success Looks Like
Child can correctly identify the sunny plant as healthier
Child can describe at least one visible difference between the two plants
Child can say (in their own words) that plants need sunlight to survive
Bonus: Child can use (or recognize) the word "photosynthesis"
