Float or Sink?

Overview

Students explore whether familiar objects float or sink in water. They make a prediction, test it safely in small groups, and talk about how the object’s material, shape and size may help explain the result. This provides an age-appropriate foundation for later learning about properties, mass, volume and density.

Learning intentions

• We are learning to predict what will happen when an object is placed in water.
• We are learning to test our predictions carefully.
• We are learning to describe what we observe using the words float and sink.
• We are learning to share our ideas and listen to others.

Success criteria

• I can say whether I think an object will float or sink.
• I can explain my prediction using “I think it will… because…”.
• I can place an object in water carefully and observe what happens.
• I can record or tell someone what I found out.

Curriculum links

• Science — Physical Science: Materials and the properties of familiar objects.
• Science — Fluids, resistance and buoyancy: making and testing predictions about whether objects float or sink in water, based on their properties.
• Science — Mass, volume and density: beginning to notice that different materials and objects behave differently in water.
• Key Competencies: thinking; managing self; participating and contributing; relating to others.

Lesson structure (40 minutes)

1. 0–5 min · Hook and wonder. Open with the opening question and mystery-object slide and show a stone and a plastic lid. Ask, “Which one will float? How could we find out?” Students silently choose, then share their ideas with a partner. Accept all predictions without confirming the answer.

2. 5–10 min · Introduce the investigation. Use the float-or-sink teaching slides to model the words predict, float, sink and observe. Demonstrate placing one object gently into a clear container, keeping hands and faces away from the water. Students practise the sentence stem, “I predict the ___ will ___ because ___.”

3. 10–14 min · Make predictions. Give each group a tray containing four or five objects, such as a stone, wooden block, plastic lid, metal spoon and cork. Distribute the picture prediction and results sheet. Students draw, circle or dictate whether each object will float or sink, with adult support where needed.

4. 14–27 min · Test the objects. Revisit the group investigation instruction slide before students work in four groups of five. Each group fills a container with water, chooses one object at a time, places it gently on the water, and records the result on the worksheet. The teacher circulates, prompting: “What did you notice?” “Did the object stay on top or go to the bottom?” “Was your prediction the same as the result?”

5. 27–34 min · Compare and discuss. Bring students together and display the results discussion slide. Groups report one prediction and result. Create a class chart with two headings: Floats and Sinks. Discuss similarities and differences between the objects, including their material, size, weight and shape. Emphasise that a prediction can be different from the result and still be a useful scientific idea.

6. 34–40 min · Plenary and assessment. Show the final reflection slide. Students turn to a partner and complete, “I found out that ___.” Finish with the prediction and conclusion sorting cards as a brief whole-class sorting routine: students help identify which statements are predictions and which describe what happened. Collect worksheets and invite two students to share a conclusion.

Resources

• Clear plastic containers or tubs of water, one per group
• Four or five familiar objects per group: stone, wooden block, plastic lid, metal spoon and cork
• Towels or trays to contain spills
• Float or sink investigation slide deck
• Float or sink prediction and results worksheet
• Prediction and Conclusion Sorting Cards
• Class chart paper or whiteboard
• Pencils, crayons and optional clipboards
• Aprons or sleeves if required

Assessment

• Listen to partner predictions and check whether students use float, sink and because appropriately.
• During testing, observe whether students handle objects and water safely, follow the sequence, and record or communicate observations.
• Use the worksheet and final sentence, “I found out that…”, to assess whether each student can connect a prediction with an observed result.

Differentiation

• Support learners with real objects, gestures and picture symbols for float and sink. Read the worksheet aloud and allow drawing, pointing, oral responses or adult scribing.
• Provide sentence starters: “I predict ___ will ___”; “I saw ___”; and “My prediction was the same/different because ___.”
• Pair students thoughtfully and give clear roles such as equipment carrier, predictor, tester, recorder and reporter. Rotate roles if time allows.
• Extend confident learners by asking them to group objects by material or shape and explain why two objects of a similar size might behave differently.
• For EAL learners, pre-teach and repeatedly model the key words, using actions: hands high for float and hands low for sink. Ensure water is comfortably accessible and offer close adult support for students with sensory or motor needs.