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Includes statements from Development Matters (birth to age five) and the relevant ELGs in full, for the Floating and sinking adult led activity
Early Learning Goal links
- Mathematics ELG: Numerical Patterns
- Understanding the World ELG: Past and Present
- Understanding the World ELG: People, Culture and Communities
- Understanding the World ELG: The Natural World
Characteristics of effective learning
Play, Be, C Units provide enabling environments with teaching and support from adults. Reflecting on the characteristics of effective teaching and learning, children will have opportunity to learn and develop by:
- Playing and exploring – children investigate and experience things, and ‘have a go’.
- Active learning – children concentrate and keep on trying if they encounter difficulties and enjoy achievements.
- Creating and thinking critically – children have and develop their own ideas, make links between ideas, and develop strategies for doing things.
Early Years Foundation Stage Statutory Framework: accessed November 2024. Available under the Open Government Licence v3.0.
What you will need
- A water tray, paddling pool, bucket or bowl, indoors or outdoors.
- A selection of familiar objects from around your setting. Try to include as many different materials, shapes and sizes as you can.
- The marine engineer poster
Duration
About 10 minutes.
STEM vocabulary to introduce
Float, sink, sunk, sank, rise, rose, risen, size, big, small, heavy, light, bottom, top, surface, under, side, shape, predict, design, test
Before you start
Show the children the marine engineer poster and tell the children that they are going to be marine engineers for this activity.
Ask the children if they know what a marine engineer does. Marine engineers make and fix boats, ships, submarines, oil rigs and drilling equipment.
Tell the children about the attributes. Marine engineers are:
Curious and want to know which materials sink and float.
Creative when they design and build things like boats, ships, submarines and oil rigs.
Resilient when their ideas or designs don’t work the first time – they try again to get it right.
Tell the children that they are going to be curious like marine engineers and investigate which objects sink and which float.
You could assess how much the children already know about floating and sinking, by asking:
- What does float mean?
- What does it mean when something sinks?
- Which objects can you think of that sink to the bottom of the water tray?
- Which objects can float on the top of the water?
What to do – step 1
Ask the children to choose an object from your selection and then ask them to make a decide whether it will sink or float when they put it in the water. You could introduce the word predict and explain that a prediction is a really good guess based on what they already know.
You could ask:
- Do you think (or predict) it will float or sink?
- Why do you think that?
- Is it big or small?
- Is it heavy or light?
- What is it made of?
Step 2
Tell the children they are going to test their prediction and ask the children to put the objects into the water one at a time.
After testing, you could ask:
- Did your object float or sink?
- Was your guess or prediction right?
Step 3
Continue to test all of the objects in your selection. Ask the children to sort them into objects that float and objects that don’t float.
You could ask:
- Do big objects always sink?
- Do small objects always float?
- What is the same about the objects that floated?
- What is the same about the objects that sank?
- Do heavy things always sink?
- Do some materials (e.g. plastic, wood, metal…) always float?
- Do some materials always sink?
- If you were a marine engineer, which material do you think you would choose to build a boat and why?
Remember to refer to the children as marine engineers and praise them for using the attributes. You could say things like:
“Well done! You have been curious like a marine engineer and discovered which things float and which things sink.”
Other things to try
Challenge the children to find natural items in the outside area will float. Ask them to collect sticks, leaves, flowers, grass, pine cones, acorns etc and test them in a tray of water.
You could ask:
- Do you predict that (object) will sink or float? Why?
- Why do you think that is floating/sinking?
- Do you think it would make a good raft or boat? Why?
- What could you do to test whether it would make a good boat?
The science of marine engineering
We have put together some useful information about the science of marine engineering to accompany this activity. Don’t worry, this is for your information only and to help you answer any questions children may have. We don’t expect you to explain this to the children in your setting!
Why do some objects sink and some objects float?
There are two forces acting on objects in the water. The weight of the object pulls it down, while the upthrust of the water pushes it up. If you’ve tried to hold a beach ball, empty plastic bottle or inflatable under water, you will have felt this upthrust force pushing the object towards the surface. The upthrust force is equal to the weight of water displaced (pushed out of the way) by the object.
If the weight of the object is equal to, or less than, the upthrust, it floats. Things that float are buoyant. If the weight of the object is greater than the upthrust, the object will sink.
Why do some heavy objects float?
An object floating on the water takes up space. To make this space, some of the water is displaced – pushed out of the way. The amount of water displaced is the same as the volume of the object that is below the surface of the water. The more weight you add to the object, the more water it displaces. As the volume of water displaced increases, the upthrust force increases to balance this, and the object floats. There will eventually be a point where the weight of the object becomes greater than the upthrust and the object sinks. To see displacement, you can fill a container almost to the top, then add stones to it, you can see the water level rise as the stones take up space in the water.
The shape of an object will determine if it will sink or float. A lump of iron, such as an anchor, will sink as it is dense and all of its weight is concentrated in one place. This makes its weight greater than the upthrust pushing against it, and so an anchor will sink. If the same amount of iron is made into the hull of a boat, it is spread over a greater area.
The larger boat displaces more water than the anchor and so the upthrust is greater. This means that the same amount of material will float in the shape of a boat, but will sink if it’s in a more compact shape.
Why do some materials float then sink (such as paper or sponge)?
Some materials are light because they are full of holes! Sometimes these are holes you can see, like in a sponge, but some are tiny holes that you can’t see, like in paper. The holes are full of air. Air is not heavy enough to push down into the water, and so materials that are full of air, float. When the materials full of air holes are floating, the water starts to fill up the air holes. The water soaks into the material and makes the weight to pulling down bigger than the force of the water pushing upwards.
