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Floating and Sinking Potatoes

Time Frame:
1 class period that runs 30 minutes.

Group Size:
Large Groups


The teacher puts pieces of potatoes in water and salt water. The students predict what is going to happen and try to name what makes this happen.

Main Curriculum Tie:
SEEd - Grade 6 (2017)Strand 6.2: Energy Affects Matter
Matter and energy are fundamental components of the universe. Matter is anything that has mass and takes up space. Transfer of energy creates change in matter. Changes between general states of matter can occur through the transfer of energy. Density describes how closely matter is packed together. Substances with a higher density have more matter in a given space than substances with a lower density. Changes in heat energy can alter the density of a material. Insulators resist the transfer of heat energy, while conductors easily transfer heat energy. These differences in energy flow can be used to design products to meet the needs of society.


  • Several potatoes
  • knife to cut them with
  • 1000 ml beaker of fresh water and 1000 ml salt water. It should be salty enough to float the potato.
  • 4 250 ml beakers to pour the water into
  • Blank paper for each student (It will be turned in when complete at the end of the discussion.)

Student Prior Knowledge:
scientific method and the steps, the properties of matter

Instructional Procedures:

  1. Cut the potato into different sized pieces. Ask before you drop a chunk in if they think that it will float or sink. Help them to recognize the scientific method. Do not tell them which water is salty or that it is any different. Just label the beakers A & B. Try big chunks and small ones. The students should write down their predictions as you go. The students have been introduced to the word “Density”. Try to get them to refer to their notes and find a word that would work.
  2. Now try mixing the water. Carefully pour 100 ml water into a beaker then carefully add the 100 ml of salty water. Ask the students to predict what will happen to a piece of potato now.
  3. Then pour 100 ml of salty water into a new beaker and 100 ml of water on top. The pouring must be done very carefully so it does not mix too much. The potato should hang in the middle. Ask them why.
  4. Have the students try to create a sentence using the word “Density” or a form of it, comparing the potato to the pure water, the salty water, and the mixed water.

Assessment Plan:
Check over the sentences

Lesson Design by Jordan School District Teachers and Staff.

Utah LessonPlans

Created Date :
Sep 30 2014 09:55 AM