Lesson 2: Testing Our Ideas
(45 minutes, then 2-4 weeks of growing and observing)
Key question: What does corn need to live and grow?
Learning Objectives
- Students will plan and conduct an investigation to test environmental factors on corn (e.g., water availability, light availability, etc.).
Materials
- Science journals
- Planning and Recording Sheet
- Corn seeds or plants (Note: if using already sprouted plants, these need to be prepared in advance)
- Plastic planting pots
- Soil wafers, sand, rocks
- Grow light
- Spray bottles
- Labels or markers
- PowerPoint (optional)
(Note: If using already sprouted corn plants, these need to be prepared in advance. Find optimum planting instructions in procedures for instruction)
Procedures for Instruction
Introduce the topic and elicit prior learning with questions such as:
- “What did we think that plants need to live and grow?”
- “Can we help Farmer Doug determine what his corn needs to live and grow?” Farmers need to consider such needs, and they need to provide the best conditions for their plants to live and grow.
- “How can we investigate the needs of corn plants?” (For instance, if we want to test whether plants need light, how would we do that? We would have to test plants growing in the light, and plants growing in the dark.)
Small groups plan an investigation: What do corn plants need to live and grow?
Planning and Recording Sheet
- Hand out the Planning and Recording Sheet to help students plan.
- Split students into small groups and have each group test one variable (e.g., water, light, soil or no-soil).
- Show them the materials they have to plan an investigation (planting pots, soil, spray bottles for water, possible grow light, items to block light, etc.), and tell them how much time they will have (consider 2 – 4 weeks if working with seeds)
- Have each group plan the conditions to test the one variable. (For instance, if students are testing the factor of light, they need to grow plants in light and in dark to compare them. “Light” and “dark” would be the conditions.)
- How many plants will they test in each condition?
- What is the total number of plants they will need?
- It’s good to have replicates in each treatment. Discuss this with your students in terms of, “If a plant doesn’t grow, how can you tell whether it was due to the condition, or if it was just a bad seed? What if you planted a few seeds in the same condition to be sure?” (a “fair test”)
(Note: Optimum planting depth of corn kernel in soil is 1-2 inches deep. Emergence of leaf above the soil will take approximately 5-7 days. Consider planting all seeds 2 weeks in advance and providing students seedlings that have been grown in the same conditions up to that point.)
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Start the investigation:
- Following the students’ plans, have them plant corn seeds in each of the different conditions they identified. OR have already sprouted plants, instruct them to create different conditions for them.
- Be sure to label each container to identify the group and the conditions. (Example: “Group A, no light”)
- Water the appropriate containers with a spray bottle.
- Note optimum planting instructions above.
Document their thinking / make predictions:
In their science journals or handout, have students draw a picture of what their plant looks like now (or the planted seed), and what they think it will look like at the end of the investigation. Have them show the different conditions they are testing.
Observe and record results over 7-28 days
- Have students water the soil as appropriate over the next 7-28 days.
- Provide brief (3-5 minute) observation times during those days / weeks for students to observe (draw) and record (describe) in their science journals the progress (or lack thereof) of their plants.