Here are a few recap facts about some materials…

Materials

Last half term we learned how we use wood, metal, plastic, glass and fabric to make most everyday objects.

We know that different materials have different properties.We use a certain material, for a certain object, because of its properties.

For example: A spoon if made from metal because it is smooth and hard. A t-shirt is made from fabric because it is soft.

Can you name some objects and explain why they are made from their material?

Wood

• Wood is a natural material. It comes from trees.

• A few things made from wood are:

• Wood is used as it can be carved in to any shape, is strong and has a very nice appearance.

furniture boats instruments paper

Fabric

• Fabric comes from plants and animals.

• A few things made from fabric are:

• Fabric is used as it is very light, warm, soft and quite easy to produce and sew.

curtains clothes towels

Plastic

• Plastics are man-made, mostly from oil.

• A few things made from plastic are:

• Plastic is used as it can be made to be flexible, hard, rough or smooth. It is also very cheap to produce and easily washable.

balls bottles carrier bags

Metal

• Metals are made from rocks. The rocks are dug up and taken to a factory where they are heated and processed into metal.

• A few things made from metal are:

• Metal is used as it is strong, hard, smooth and easily washable.

jewellery cutlery cars

Glass

• Glass is made from very fine sand. It is heated until it melts.

• A few things made from glass are:

• Glass is used as it is strong, hard, smooth, easily washable and transparent.

bottles light bulbs glasses

Percy would like you to be a scientist this afternoon.

The storm washed many household items into the river and Percy isn’t sure if he will find them floating on top of the water or under the water because they have sunk.

Percy has lost a lolly stick, some money, an apple, some stones, marbles, a ball and a sponge.

Could you help Percy by carrying out a sinking and floating experiment to find out where the items might be.

What does Percy mean by sinking or floating?

Some objects stay on top of the water – this is called floating

Other objects fall to the bottom –this is called sinkingsinking

floating

Let’s carry out a test and try these objects in a container of water and see what happens.

Float or Sink?How do we know if an object will float or sink?

a lolly stick

a stone an apple

a spongea coina bouncy ball

a marble

Make a prediction in your book before you try each object. It might help to hold and feel each object. Then, see if you were right.

Does it float or sink?

Density

Why Do Some Objects Sink?Which items sank? Which floated?

Objects like marbles, coins and stones are more dense than water. Their tiny molecules are really close together. When you put them in water, they sink to the bottom. Remember this not linked to weight, boats are heavy but they still float!

But objects like wood and sponges are less dense than water. Their tiny molecules are further apart so they float on water. Objects that are hollow (with air inside) also float. This is because air is less dense than water.

Does the Shape Matter?

What about shape?

The shape of an object matters too. When more of the surface of an object is touching the water, the object floats better. Let’s try that next.

What do you think will happen if you drop a ball of plasticine into water?

TEST IT OUT – record your predictions in your book or on your sheet

Does the Shape Matter?

Yes! It sinks because the material is more dense than water.

This time, change the shape of the ball into a boat shape. Can you make it float?

Buoyancy

When more of the shape is touching the water it is more likely to float. The object pushes against the water, but the water pushes back! If lots of the object is touching the water, the water will push back enough to make the object float! This means the object is buoyant (even if the material is dense).

Can you make the boat sink by adding stones or marbles to it? How many does it need to make it sink?

Real Life

Boats can float on the water because they are less dense than water. The hull of a boat is hollow and the shape helps it to stay buoyant as well.

Carry on experimenting