Sink or float

Why some objects sink and some float

Resource Info

Basic Information

Why do some objects float while others sink? The activity and poem introduce children to the concept of sinking and floating, without bringing up terminology like density.

(All day)

Children are fascinated to observe how some objects float and some sink. Explain the concept to them through this activity.

Activity Steps: 


  • 1 tub half filled with water
  • Assorted objects that sink and float (sponge, wooden block, pencil, eraser, empty lunch box, etc.)


  1. Explain the concept of ‘sink’ and ‘float’ to the children.
  2. Put each of these objects one by one into the water.
  3. See which object falls to the bottom and which one stays afloat.
  4. The children can say ‘sink’ or ‘float’ as relevant.


Preparation to be done the previous day

  • Divide the class into 2 teams ‘Sink’ and Float’.
  • Ask each child to bring any one object that sinks or floats, depending on the team he/she is in.
  • Each child should also be asked to necessarily bring a napkin (to dry the object and perhaps themselves).


  • 2 tubs half filled with water, 1 tub labeled ‘Sink’ and 1 labeled ‘Float’.
  • Any 10 items commonly found in the school, just in case any child forgets.
  • A couple of spare napkins, just in case any child forgets.
  • 2-3 mopping cloths to spread around the table where the tubs are kept.


  1. Call out each child one by one. Ask them which team they are in.
  2. Let them put their object into the corresponding tub. If they are right, they go back to their team. Otherwise, they go and sit with the opposite team.
  3. The team with the maximum number of students wins.

Note for the teacher

Can any child make an object that floats, sink (putting something into an empty lunch box)?
Can any child make an object that sinks, float (a ball of clay or foil or ‘atta’ which can be made
into a boat)? This can be another activity as described in ‘Float boat’

Sing this rhyme with your class

Floating and Sinking

Why do things float?
Why do things sink?
What do you think?
What do you think?
Things that float
Are lighter than water.
That's why they float.
That's why they float.
Things that sink
Are heavier than water.
That's why they sink.
That's why they sink.

Meish Goldish, 101 Science Poems & Songs for Young Learners, Instructor Books

17583 registered users
6684 resources