Before your child carries out this experiment, the next time he has a bath, draw his attention to the fact that some of his toys always float, and yet the soap sinks to the bottom of the bath. Tell him that he can investigate this further the next day.

You will need::

• An assortment of small objects, some that float and some that sink, such as a teaspoon, mug, bath toy, cork and sponge
• Large bowl half-filled with water
• Paper
• Pencil

There may be some splashing, sp protect the tabletop. Put all the small objects on to a tray. On the sheet of paper, draw an outline of the side of the bowl with a line to mark the water level.

• 1. Put all the objects in a row in front of your child, with the bowl of water behind them. Say that he is going to find out which objects float, and which sink.
  2. Pick up the first object in the row and say whether you think it will float or sink. Drop it into the water gently. Invite your child to estimate, and then test the rest of the objects, as to whether they float or sink.
  3. Help your child to record what happens by drawing the objects on a picture of the bowl. Show the objects above and blow the waterline as they sink or float.
     

Other activities:

1. After he has recorded his findings, discuss with him what the objects are made from. Encourage him to conclude that certain materials are better at floating than others.
2. If you are using a sponge, your child should see that the sponge will float at first, but as it becomes heavier with water, it will sink.
3. Repeat the same experiment, but this time add salt to the water to see how this affects the floatability of the objects.
4. Take your child to look at boats, and to see what boats are made from. Introduce him to the word Fibreglass and explain what kind of material it is. Ask him questions like, “why are boats made out of fibreglass”? If he is not sure, remind him about floating and sinking experiment. Also point out the shape of the boat and explain how it helps the boats to float