Floating and Sinking

A fun, interactive and challenging science day designed to investigate the concepts of floating and sinking. The day was created for a year one year group however it could be adapted for any year group or class. 


To learn about different materials that float and sink.

To design a boat that can float on water and test it.

To ask questions and recognise they can be answered in different ways.

To use observations to suggest answers to tests.

To gather and record data to answer questions.


Overview of the day:

15 minutes – Whole class/year input – see notes sheet

45 minutes – Boat design session – see boat design sheet

10 minutes – Read ‘Who sank the boat?’ during snack time or after break.

2 hours – The children will then move through a rotation of activities. They will spend 30 minutes on each activity. Each activity should be supported by one or two adults depending on whether it is a class or year group science day.

Making and testing the boat

Resources: recycling, scissors, celotape, water trays, design sheets

The children should use their design sheet to build the boat using recycling that they have brought in from home. Once the boats are built they will test their boats in the water trays outside. Once they have tested their boats they should fill in the bottom of the design sheet to show whether their boats floated or sank. The adults should prompt them to think about why their boat floated or sank. Take pictures for their books and displays.

Teacher notes: if the boat is made from water proof materials (plastic) and is light and stable it will float as we know that light/waterproof objects float. If the boat is made from non water proof materials or is heavy or unstable it will sink as we know that heavy non waterproof objects sink. If the boat is made from paper/cardboard it might float to start with as it is light however once the paper/cardboard absorbs the water it becomes heavier and so the boat will sink.

Experiment task

Resources: a collection of materials from the classroom (blocks, felt, ruler, rubber, stone, pencil, wood, plastic etc), a tub of water, sugar paper and pens to make a floor book

Children given a collection of materials, objects and a tray filled with water. Tell the children that you want them to come up with an experiment to look at what objects float and what objects sink. They need to think of a scientific question such as “do all heavy objects sink?” and then create an experiment to test it. Give them lots of time to talk. At certain points stop them and ask them questions about what they are doing. Try to encourage scientific enquiry and discussion using words such as prediction, hypothesis, testing, findings, floating and sinking. Create a floor book with each groups scientific question, method, materials and results. Take pictures for their books, the floor book and displays.

Plasticine Challenge

Resources: Plasticine, water trays, cubes, laminated prompt sheets

Children are given a piece of Plasticine and asked to see if they can make a boat that will float on the water. They have to try and make a boat that will float and then see how many cubes they can put inside the boat before it sinks. Tell the children there will be a prize for the team who can make the boat that carries the most cubes. Ask them to think about what they have to do to the boat to make it float. Encourage the children to discuss the scientific reasons behind what they are doing as they make their boat, test it, adapt it and test it again. Take pictures for their books and displays.

Teacher notes: a successful boat needs to have a large flat base so that it can carry cubes and have small sides to keep the water out. The base needs to be thin so that it is not too heavy and doesn’t sink. If the boat is too heavy it will sink and if the sides have holes in them or are too short water will get in making the boat heavier and causing it to sink.

Poster making (can be done independently)

Resources: plain A4 paper, images of things that float, coloring pens and pencils

Ask the children to make a poster showing things that float. Ask them to think about both drawing and writing. Provide them with images of things that float and an example poster.

15 minutes – Whole class/year evaluation

Bring the children back together. Show them the Venn Diagram and ask them what the diagram shows them – does it prove or disprove our hypothesis. Then ask the children to share a few examples of what they saw during the day that proved or disproved their hypothesis.

Finally ask the children to show you thumbs up if they enjoyed the day and thumbs down if they didn’t enjoy the day. Ask different children to share what they enjoyed and what they would have changed.


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