University of Virginia
Physics Department

Convection Currents and Density

A Physical Science Activity

Student Activity

Materials (for each group)



  1. Obtain an ice cube that has been strongly dyed with food coloring.
  2. Using tongs, gently place the ice cube in a beaker full of warm, fresh water. Keep the beaker and water as still as possible.
  3. Observe the ice - water mixture for several minutes. Write a detailed description of your observations.
  4. Measure the temperature at the surface, at the bottom of the mixture, and 3 measured levels in between. Record the temperatures in the data table.
  5. Empty the beaker and fill it to the same level with warm water.
  6. Add salt to the water, stirring vigorously as you pour until no more salt will dissolve.
  7. Repeat steps 3 and 4 using salt water in place of fresh water. 


Data Sheet

To print out the Data Sheet only, click here.


Observations of Fresh Water:



Fresh Water
Salt Water
surface   surface  
1/4 Down   1/4 Down  
1/2 Down   1/2 Down  
3/4 Down   3/4 Down  
Bottom   Bottom  

Observations of Salt Water:




Answer the following questions:

  1. As the ice melts, what happens to the colored meltwater in the sample of fresh water?

  2. In the salt water?

  3. Do you observe convection currents in this activity?

  4. Of the 2 liquids used, which do you think is denser?