Teacher Background:

Students will learn about the law of conservation of mass. They will conduct several experiments and make graphs to show that mass is conserved. Students will discover that substances do not disappear when they dissolve; they just change state.

Lesson Plan:

  1. Prior to this lesson, gather the following supplies for each pair or group of students:
    1. Skittles
    2. Water (slightly warm)
    3. Plastic bowls
    4. Salt or sugar (optional)
  2. Write one of the inquiry questions on the board and have the students read the article “How Does Water Dissolve Other Substances”.
  3. Optional: Show them the phenomenon video “What Happens to the Mass of an Object When It Dissolves?”. (You must be logged into your Studies Weekly Online account to view the video.)
  4. Next, have the students work in pairs or small groups. Give each group their set of materials. Encourage them to find a place to set their bowl where it will not be bumped up against or knocked over.
  5. Make a circular pattern in the bottom of the bowl. The Skittles should look like a ring sitting in the bottom of the bowl. Try not to have them touching each other.
  6. Pour water into the bowl so that it reaches all the candies and barely covers them with water. Optional: have the students time how quickly the water starts to dissolve the candy.
    1. What do you notice?
    2. What do you wonder?
    3. Why don’t the colors mix? (the candy shell in each piece is covered equally and so it dissolves at an equal rate.)
  7. Have the students fill out the first box of the graphic organizer Observations.
  8. Repeat the experiment using salt water and then sugar water. Have the students make predictions about what will be different using the different types of water. Try making different types of patterns.
    1. What do you think will happen in the salt water? (slows the process down because the water is now more dense with the salt in it)
    2. What do you think will happen in the sugar water? (slows the process down because the water is now more dense with the sugar in it)
    3. What do you think would happen if we used cold water? 
    4. What would happen if you moved one of the candies?
    5. What would happen if you added a candy piece?
    6. Do you think the candy tastes different now?
    7. What do you think would happen if we bumped the bowl?
  9. Have the students fill out the graphic organizer for the other two sections with their observations. You may need to have students alter the graphic organizer depending on the experiments you choose to do as a class.
  10. On the back have the students write a summary of the experiment.
Inquiry Questions:
  • What happens to the mass of an object when it dissolves?
  • How does water dissolve other substances?
  • Dissolve
Notes for Teacher:

This lesson gives students the opportunity to watch as an object dissolves, breaks into smaller pieces and changes its state.

Well-Being Questions:
  • How does experimentation help you learn new things?
  • How does collaboration help you when you experiment?
  • What can you do when an experiment fails?
Let’s Write:

Write out the instructions for an experiment. Be sure to include every step so that someone can follow your instructions and be successful.

Materials Used:
  • Skittles (the brand name works best)
  • Water (slightly warm)
  • Plastic bowls
  • Salt or sugar (optional)
Related Media:
Graphic Organizers:
  • Observations
Studies Weekly graphic organizer observations for science lesson plan

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