Will it float?
Floating and Sinking
These activities are best done using a clear container full of water but can be done using a washing up bowl, bucket, in the sink or bath.
Water has many fascinating properties that young children love to explore.
Understanding why some things float and others sink is not as simple as it appears. Having lots of opportunities to experience 'floating, sinking and sunk' is the best way to build up this aspect of scientific knowledge.
Ask your child, What does the word float mean? What do we mean when we say something sinks?
To find out more about your child's experiences and ideas about floating and sinking ask, What objects can you think of that sink? What objects stay afloat?
Investigate a selection of objects that float or sink, such as corks, lolly sticks, lids, foil dishes, cotton reels, plastic and metal teaspoons, marble, conker, coin, bottle tops, sponge. Include different fruits and vegetables to see whether they all behave in the same way.
Encourage your child to handle the different objects and to predict whether they think they will float or sink. Ask questions such as What is it made of?
Will it float or will it sink?
Can you think why?
Do you think bigger things always sink?
Or rather than giving your child the objects to investigate set them the challenge of going on a scavenger hunt around the house to find objects that they think will float and objects that they think will sink! As they are making their choices ask them why they think it will float/sink. Talk about the materials the objects are made of and how heavy/light the object feels. Ask questions to stimulate their thinking and formulate their ideas.
Ask your child to put the objects into the water one by one and observe what happens.
Do they stay floating on the surface?
Do they sink to the bottom?
Do they sink to the bottom and the float back up to the surface of the water?
Do they float at first and then sink to the bottom?
Whilst there will be great enthusiasm and urgency to find out what happens. Lots of valuable observations and learning could be missed by putting all the objects in at once.
Ask questions such as: Was your guess (prediction) right? Do some objects always float?
You can record the results of the children's investigation either by drawing the objects on two charts labelled 'objects that sink' and 'objects that float', or simply by placing the objects in separate bowls.
Science investigations can often generate a lot of questions! Even though some of the science behind the fun can appear a little too complicated for young children it is important to start introducing them to new words and ideas, as this will provide important stepping stones in their learning.
Objects like coins, rocks, and marbles are more dense than water. They will sink. Objects like apples, wood, and sponges are less dense than water. They will float. Many hollow things like empty bottles, balls, and balloons will also float. That is because air is less dense than water. This is one reason huge ships can float, even though they are very heavy. Inside a ship, there is a lot of hollow space filled only with air. But that’s not all, shape matters, too!
The outside of an object is called its surface. When more of the surface is touching the water, the object is more buoyant, which means it floats better. When an object floats, it pushes water out of the way. That is called displacement. But guess what? Water pushes back! So the more surface area an object has, the more water pushes back against it, helping it float. That is another reason why even big ships do not sink if they have the right shape.
Need a challenge?
You can test this out. Try making a boat with a flat bottom using tinfoil. Does it float? What happens if you start putting pennies or pebbles inside your boat? What happens if you crumple your tinfoil boat into a ball? Using what you have learned about density and buoyancy, why do you think the empty boat floats best?
Need another challenge?
Watch the story Who Sank the Boat? by Pamela Allen
Look carefully at the pictures to see what is happening. Draw attention to where the animals sit in the boat to try to balance their weight. Ask
What happened to the boat when the cow got in? Why?
Can you find pictures where the boat is balanced?
Look at the story again and focus on observing what is happening to the boat in the water.
Who did sink the boat?
Why do you think that happened?
Encourage your child to act out the story in the water using their small-world toys and using a plastic container as a boat.
How many toys can you fit in their boat before it starts to sink?
What happens if the passengers are all on one side of the boat?