# Lesson 142: Experiment — sink or float

🔬 SCIENCE (40 Lessons) • 🟡 C. Materials and Matter

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## Objective

I can do a simple sink or float experiment. I can predict what will happen, test my ideas with water, and record which objects sink and which float.

## Materials

- Large clear bowl, basin, or sink half full of water
- Small objects that can get wet (for example: plastic spoon, metal spoon, rubber ball, coin, pencil, small block of wood, bottle cap)
- Simple table drawn on paper with columns: "Object", "Will it sink or float?", "What happened?"
- Towel for drying hands and objects
- Pencil or crayon
- Adult help for safety around water

## Mini-lesson — What does sink or float mean?

When we put things in water, some things go to the bottom and some stay on the top. We call this sink or float.

Sink

- If an object sinks, it goes down to the bottom of the water.
- We can say, "The coin sinks".
- Many metal objects sink in water.

Float

- If an object floats, it stays at the top of the water.
- We can say, "The plastic ball floats".
- Many wood and plastic objects float.

Heavy and light for their size

- Some objects feel heavy for their size. These often sink.
- Some objects feel light for their size. These often float.
- Shape and material matter too. A metal coin may sink, but a big metal ship can float because of its shape.

Doing a fair test

- Use the same bowl of water for each object.
- Drop each object in gently from near the top of the water.
- Write down your prediction and the result for each test.

Scientists make a prediction, do a test, and then record what really happened. You are doing science when you test sink and float.

Picture strip: Sink or float in a bowl of water

Float

Sink

## Guided Practice — Try a sink or float test

You will choose a few objects, predict if they will sink or float, then test them in water with an adult.

1. Prepare the water: With an adult, fill a bowl or basin halfway with clean water. Place a towel nearby.
2. Choose objects: Pick safe objects that can get wet, such as a plastic spoon, metal spoon, small wood block, toy car, rubber ball, bottle cap, and pencil.
3. Make predictions: On your table, write the object name and write "sink" or "float" in the prediction column.
4. Test gently: With adult help, place one object at a time on the water. Watch what happens. Does it go to the bottom or stay on the top?
5. Record results: In the result column, write what really happened, using words like "sank" or "floated".
6. Talk about why: For one or two objects, say why you think they sank or floated. Use words like heavy, light, wood, or metal.
7. Use the tracing pad: Choose words like sink, float, water, or test and trace them. Say the word and a short sentence as you write, such as "The ball floats".

Tracing Pad
Lines
Trace
Pen

## Practice 1 — Predict and test

Use your table to write predictions and results for a few objects.

1. Draw a simple three-column table with headings: "Object", "Will it sink or float?", and "What happened?".
2. Choose at least five small objects. For each one, write the name in the first column.
3. In the second column, write your prediction: "sink" or "float".
4. Test each object in water with an adult and write what really happened in the third column.
5. Circle any objects where your prediction was different from the result and talk about why.

## Practice 2 — Sort pictures into sink or float

Sort drawn or printed pictures into "Sinks" and "Floats".

1. Draw two big boxes on your page. Label them "Sinks" and "Floats".
2. Draw small pictures of objects such as a coin, stone, wood block, plastic bottle, paper boat, and rubber ball.
3. Think about each object. Where would you place it after a water test?
4. Write or draw each object in the box where you think it belongs.
5. With an adult, test one or two of the objects if it is safe. Check if your sorting was correct and move any that need to change.

## Practice 3 — Explain your thinking

Use sentences to explain why some objects sink and others float.

1. Choose two objects that sank and two objects that floated in your experiment.
2. For each object, write one sentence that starts with "It sank because…" or "It floated because…".
3. Use simple ideas like "It is heavy for its size", "It is made of wood", or "It is full of air".
4. Read your sentences to an adult and see if they can tell which objects you mean.

## Quick Check — Experiment: sink or float

Answer each question about sink, float, and water tests. Think about what you saw in your experiment.

1) What does it mean if an object sinks in water?

It goes down to the bottom. It stays at the top. It disappears forever.
When an object sinks, it moves down to the bottom of the water.

2) What does it mean if an object floats in water?

It breaks apart. It makes the water disappear. It stays on the top of the water.
Floating means the object stays on the surface of the water.

3) Which object is most likely to sink in water?

A small wood block. A metal coin. A plastic bottle cap.
Metal coins are usually heavy for their size and sink in water.

4) Which object is most likely to float in water?

A rubber ball. A stone. A metal key.
Rubber balls are light for their size and often float.

5) What should you do before testing an object in water?

Throw it hard into the bowl. Close your eyes. Ask an adult if it is safe to put in water.
Always check with an adult if an object is safe to put in water.

6) In a fair test, you should…

Use the same bowl of water and drop each object in gently. Change the water level every time. Throw some objects hard and some softly.
A fair test uses the same conditions for each object.

7) A child says, "I think this wood block will float." This is a…

Result. Prediction. Spill.
Before the test, we make a prediction about what we think will happen.

8) After testing, you write "The coin sank." in your table. This is the…

Guess. Question. Result.
What really happened in the test is the result.

9) Which sentence about sink and float is true?

Some objects sink and some float, and we can test them in water. All objects always float. All objects always sink.
Different objects can sink or float. We find out by testing.

10) Which is a good safety rule for a sink or float experiment?

Splash as much water as you can. Keep water in the bowl and clean up spills quickly. Put electrical things into the water.
We keep water in the bowl, dry spills, and never put electrical items in water.

11) Which object is most likely to float in water?

A metal coin. A stone. A small plastic bottle with air inside.
Objects full of air, like empty plastic bottles, often float.

12) A child says, "The metal spoon is heavy for its size." What did they notice?

How the spoon feels in their hand. The color of the spoon. That the spoon is made of paper.
Heavy for its size is something we feel when we hold an object.

13) If your prediction was wrong, what should you do?

Erase the result. Keep the result and think about why it was different. Stop doing science.
It is fine if predictions are wrong. We learn by keeping the result and thinking about it.

14) Which picture would best match "sink or float experiment"?

A child drawing a tree. A child jumping on a chair. A child gently placing objects into a bowl of water.
A sink or float experiment uses water and objects to test what happens.

15) Why do we do sink or float experiments?

To learn about materials and how they behave in water. Only to make a mess. So we never use water again.
Sink or float experiments help us understand materials and water in a hands-on way.

## Assessment (parent/teacher)

Student can explain what sink and float mean in simple words. Student can make predictions about whether objects will sink or float. Student can carry out a simple sink or float test safely with water. Student can record results in a simple table or list. Student can give short explanations for why some objects sink and others float.

## Exit ticket (student)

😀 I can explain sink and float and talk about my experiment. 🙂 I know some facts about sink and float but still need more practice. 😅 Sink and float still feel a bit tricky to explain.

#### Next time I will practise…

Making predictions before I test Recording my experiment results clearly Explaining why objects sink or float in my own words
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