6. Predict if an object will float or sink

Lesson Recap Starter: Think back to the last lesson. When riding a bike up a hill, how do gears work to make pedalling easier?

Lesson Starter: Why do some things float and some things sink? 

Encourage children to think about different materials. 

Presentation - Starter Slide

bowl

water

marble

ping pong ball 

pen 

handout 

scales

Answer questions and take part in activities during the presentation. 

On slide 6, the children will be asked to name the downward force acting on the boat. They may describe this as gravity but it is in fact weight. This misconception will be addressed within the expert film. 

Use the simulation to describe how the concept of density relates to an object's mass and volume.

Key Concept:

During this unit, each lesson contains a key concept question housed in the '30 Second Challenge' slide. To help children master this content so the knowledge moves from their short term memory to their long term memory, at the beginning of the follow on lesson the question from the previous lesson is revisited. 

The questions covered during this unit include:

What are the highlights of the life and work of Sir Isaac Newton?

What is the difference between gravity and air resistance?

What's the difference between water resistance and friction?

Explain how a lever and a pulley can make it easier to complete a task. Use an example to explain your answer.

When riding a bike up a hill, how do gears work to make pedalling easier?

Why do certain objects sink or float and what does density have to do with it?

Presentation
Mini whiteboards

PHET Slide

Expert Film: Shows a density column being made from different liquids. Ensure children understand that the downward acting on an object whilst in a liquid is weight, rather than gravity. 

How we deliver the Gatsby Benchmarks:

2 - Learning from career and labour market information:  Pop along to Developing Experts career’s zone to find out about jobs in your area.

4 - Linking curriculum learning to careers: This unit showcases careers that relate to forces. Access our 360° virtual work tours.

7 - Encounters with Further and Higher Education: Pop along to Developing Experts career’s zone to find out about training providers in your area.

Presentation

Sink or Swim?

1. Pupils should look at the objects and predict whether each object will sink or float before conducting their tests. They should record their results in the table on the Handout.
2. Students should measure the mass of each object on a mass balance and record this in their table.
3. Then using the volumes provided calculate the density of the object. They can calculate the density by dividing the mass by the volume.
4. Then place the object into the container of water to see if it sinks or floats and record this on their table.

Once children have completed the practical, they should use their results to explain the relationship between density and floating and sinking. Objects with a low density will float and objects with a high density will sink. 

If an object's density is greater than one, it will sink; if an object's density is less than one, it will float.  This is because water has a density of 1g/m3.

Children could also think about which material would create an effective buoyancy aid. Finally, children could draw a chosen object within their experiment. They should use arrows to demonstrate the different forces acting on the object, ensuring the arrows are drawn to the correct size. They should label the arrows. 

Sink or Swim?

Container filled with water

tennis balls

golf balls

marbles

ping-pong balls

base 10 cube

Calculator

mass balance/ scales

Handout

Quiz

With their talk partners, the children are to go through the quiz at the end of the presentation and answer the questions.    

Quiz in Presentation