Photosynthesis: How Plants Make Their Own Food (And Ours)
Students learn that plants make their own food through photosynthesis, a process that uses sunlight, water, and carbon dioxide to produce glucose and oxygen. The lesson builds from a warm-up observation through guided note-taking, a live demonstration showing the plant releasing water vapor, and ends with an exit ticket connecting photosynthesis to the air students breathe.
Materials
- potted plant (any leafy houseplant) (1)
- clear plastic sandwich bag (1)
- twist tie or tape (1)
- photosynthesis diagram handout (24)
- colored pencils (green, yellow, blue) (one set per pair)
- exit ticket slips (24)
Lesson plan
Opening: discussion (5 min)
If plants make their own food out of sunlight, water, and air... why do farmers still need to water crops? Talk to your partner for 90 seconds.
Demonstration
Seal a plastic bag around one leaf at the start of class. By the end, students see water droplets forming — physical evidence the plant is releasing water vapor from photosynthesis.
Needs: clear plastic sandwich bag, twist tie, live plant
Tip: If time allows, do the demo on two plants — one in sunlight, one covered with a box. The covered plant produces less condensation. Evidence that light matters.
Steps
- 5 min
Teacher: Hold up the plant. Ask: 'If I forgot to water this for a month, what would happen?' Let students picture it. Then: 'What if I put it in a closet with no light for a month — same problem, or different problem?'
Students: Respond verbally. Some will say 'it dies' for both — press them to explain WHY each one kills the plant.
- 10 min
Teacher: Introduce 'photosynthesis' and write the equation in plain language: sunlight + water + CO2 → glucose + oxygen. Emphasize: 'Plants make their own food. They don't go to the grocery store.'
Students: Copy the equation onto the diagram handout. Color inputs and outputs.
- 8 min
Teacher: Demonstrate: seal the plastic bag around one leaf. Explain students will check it at the end.
Students: Watch demo. Predict what they'll see.
- 12 min
Teacher: Pair students. Each pair fills a 3-column chart: INPUT | SOURCE | WHY NEEDED. Circulate.
Students: Work with partner to complete chart.
- 5 min
Teacher: Reveal the bag. Ask: 'What do you see? What does that tell us?'
Students: Observe condensation. Discuss what it proves.
- 5 min
Teacher: Distribute exit tickets. Students complete individually.
Students: Complete the exit ticket.
Guided practice (12 min, pair)
Students work in pairs to complete the 3-column INPUT/SOURCE/WHY NEEDED chart while the teacher circulates and checks understanding.
Check for understanding (exit ticket, 5 min)
- Name the three things a plant needs for photosynthesis.
- Name the two things photosynthesis produces.
- What did the water drops in the plastic bag prove?
Answers are on the Answer key tab.
Teacher notes
5th graders often think plants 'eat' dirt or water. The key move is the sentence 'plants build their own food out of air, water, and sunlight.' Slow down at that moment. For struggling learners, keep the diagram on the board throughout. For advanced learners, ask what happens to plants at night.
Discussion prompts
- If plants make their own food, why do we fertilize them?
- Could a plant survive on Mars?
- Why are rainforests called the 'lungs of the Earth'?
Vocabulary
- photosynthesis: The process plants use to make food from sunlight, water, and carbon dioxide. (e.g. Every green leaf is doing photosynthesis right now.)
- glucose: A type of sugar that plants make and use as food.
- carbon dioxide: A gas in the air that plants take in through their leaves. (e.g. We breathe it out; plants breathe it in.)
Common misconceptions
Students may think: Plants eat dirt.
Actually: Plants absorb minerals from soil, but minerals are not food. Plants build their own food via photosynthesis.
What to do: If a student says this, ask: 'What would happen if we put a plant in nutrient-rich soil in a closet with no light?' Then walk them through why it would still die.
Differentiation
Students who need more support: Pair with a strong partner for the chart. Provide a word bank (sunlight, water, CO2, glucose, oxygen). Keep the diagram visible throughout the lesson.
Students ready for more: Ask: 'If photosynthesis needs sunlight, how does a tree survive winter when days are short?' Let them hypothesize before explaining stored glucose.
Multilingual learners: Provide diagram labels in student's home language where possible. The visual equation transcends language.
Accommodations
Vision / reading: Provide a tactile version of the photosynthesis diagram (raised lines or felt arrows). Enlarge the equation on the anchor chart to at least 36pt. Describe the demo bag aloud as it forms droplets for students with low vision.
Hearing / listening: Post the three inputs and two outputs on the board in written form alongside the oral equation. If a student wears FM/hearing technology, face the student when saying the key equation words.
Movement / writing: Pre-label the diagram handout for students with fine-motor difficulty (students circle rather than write). Allow voice response on the exit ticket.
Attention / learning: Pre-teach the words 'photosynthesis,' 'glucose,' and 'carbon dioxide' a day before the lesson. Provide the 3-column chart partially filled in for students who need scaffolding. Break the equation into inputs-first, outputs-second.
Emotional regulation: Allow a fidget tool during the 12-minute partner chart work. Offer a quiet reset spot near the teacher desk if the demo's anticipation gets overwhelming.
Other: The demo itself is low-sensory (quiet, visible over time), which helps most students. Position the plant so every student can see without crowding; crowding is the primary behavioral trigger for this lesson.