Density is a measure of how heavy an object is compared to its mass. Liquids can have different densities and float on top of each other.  We are going to use our science ‘Magic’ and make potatoes float at different levels in a bottle or test tube by changing the densities of the liquid they are in.







1. Water can be a slip hazard, clean up any spills immediately.



  • sink or swim step2bFill the test tubes (or cups) with water.
  • It is easiest to make up the most concentrated sugar solution first, so that the potato floats on top.



  • sink-or-swim-step2Shake the test tube (or stir in a cup) until dissolved.
  • Once the most dense solution is made, pour a little into the other test tubes and fill with water until the desired density is achieved.



  • sink-or-swim-finalThe first test tube has pure water (no sugar).
  • The others are a mixture of the concentrated solution and water.



Check out the ‘Wacky Science’ video of this experiment and ‘What’s Going On’ series link. They are currently ‘In Production’, so check back soon…..


Wacky Science Ep

What's Going On?


We have explored density many times in our Looney Lab experiments. But if this is your first time, then density is a measure of how heavy or loght an object is. Specifically, it is a measure of how much mass there is in a specific volume. Consider the two balls below:

density ball pic


The MORE masss there is for a volume the more dense it is.

In our experiment, we added different amounts of salt to water. The water having the most salt has the higher density and sinks below the potato causing it to float. If the water has the same density as the potato, the cube of potato floats in the middle. If the potato is more dense than the water it sinks.

The ‘Dead Sea’ is a lake near Jordan and Palastine that is nearly 10X saltier than the ocean. It is called the dead sea because it is so salty, no animals can live in it BUT it makes a great sea to float in. The high salt content makes the water VERY dense and you can float in it easily (just like a boat).

Girl floating at the Dead Sea, Jordan




If you would like

– more details,

– pictures of the second half of the experiment

– information on how to investigate this further

– links to everyday examples

– management hints & teaching pointers (5P Teacher develpoment program)

 ….. then why not subscribe to one of the following


(1) Crazy science Club

Crazy Science Club slider5

(2) 5P Teacher Training course called ‘Looney Lab  Classroom Creations

Looney Lab Classroom Creations2


Or you can purchase the ‘Bright Sparkes Guide’ of this demonstration only ($2.50) which has:

    • HD pictures of experiment steps
    • Detailed explanation of science
    • Mini-challenge section (another experiment)
    • Making it a ‘Scientific Method’ experience
    • Graphing opportunities
    • REAL links and descriptions to everyday examples of concept.