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Lesson Plan #: AELP-GLG0203
Submitted by: Brittnie Burke and Pamela Choc
Email: abaigael@hotmail.com, pammy@selway.umt.edu
School/University/Affiliation: University of Montana
Endorsed by: Lisa Blank
             University of Montana

March 29, 2001

Grade Level: 1, 2


  • Science/Geology

Duration: 90 minutes

Description: Students will learn about the sizes and characteristics of different types of rocks. Students will also learn how rock particles are distributed.


  • Students will demonstrate different ways of sorting rocks.
  • Students will conclude that when shaken, the larger objects of a mixture will rise to the top of the mixture, while the smaller objects will sink to the bottom of the mixture.
  • National Science Education Standards : Science as Inquiry and Earth Science: Properties of Earth Materials will be fully addressed.
  • Objectives:

  • Students will study an array of rocks and brainstorm ways to sort them.
  • Students will classify the different types of rocks present into three size categories.
  • Students will be able to predict how a mixture of rocks/objects will separate.
  • Materials:

    • clear container with different sized rocks (pebbles, gravel, sand)
    • clear container with three different sized objects (small beads, large beads, large marbles)
    • mixture of pebbles, gravel, and sand for each student
    • small clear containers for each student, filled with rock mixture
    • rubber bands 
    • plastic wrap (use with a rubber band as lids for the cups of rocks)
    • paper plate for each student
    • hand lens for each student
    • prediction sheet
    • Prediction sheet in .pdf format; requires free Adobe Acrobat Reader.

      Click the icon to obtain the free Reader.


  • Pebbles – Pebbles are the largest of the three rock forms. They range in size from that of a small marble to that of a small pea.
  • Gravel – Gravel is smaller than pebbles, yet larger than a grain of sand.
  • Sand – Sand is the smallest of the three rock forms. It is worn into fine granules by erosion.
  • Mixture – A composition of two or more substances that are capable of being separated.
  • Sort – To arrange according to class, kind or size.
  • Prediction – To make an educated guess as to the outcome of a situation.
  • Procedure:
    Scientific Explanation – Teacher Information/Background:
    What are some ways of separating a mixture of rocks? The processes of the earth, such as physical and chemical weathering, have broken down the earth’s surface, creating a mixture of different sized rock particles. The size and distribution of rock particles gives geologists clues about earth-shaping processes. Students can simulate some of the processes that separate rock particles in the natural world by shaking, sifting, and mixing pebbles, gravel, and sand. Each separation provides students with a little more information about the properties and behaviors of earth materials. When a mixture of rocks is shaken, the larger rocks will move to the top layer. The smallest rocks will move to the bottom layer, because they slide through the larger spaces between the larger rocks. 

    Focus Phase:
    Have you ever played with rocks on the playground? What did you notice? Are all of the rocks the same? How are they different? (Wait for the students to mention the different sizes of rocks.) Explain that nature creates a mixture of rocks. Scientists need to sort these rocks in order to study them. Give each student a hand lens along with a paper plate containing a mixture of rocks. Ask students to observe the mixture and be prepared to discuss their observations. What did you notice about the rocks? Approximately how many different sizes are there? (Make sure they see that there are three different sizes.) How can we separate rocks of different sizes? Show students a large container of various sized rocks. What if the rocks cannot leave the container? (Experiment with and discuss some of their predictions.) Once shaking the jar is suggested, give each student a copy of the prediction sheet. [ Author’s Note: Duplicate the prediction sheets so that they are double-sided.] Students will draw their predictions of how the rocks will look (according to size) after being shaken. Students can draw their pictures in the first empty jar on the prediction sheet. 

    Challenge Phase:
    Have students experiment with separating a mixture of rocks by giving each student a container filled with a mixture of rocks. Students may shake the container, roll the container, or any other methods that they think of. After this free exploration period, discuss their findings. What methods did you try? What happened when you tried them? Did you notice anything about the placement of the different sized rocks? (If not, let them observe and experiment for a few more minutes.) Why do you think they separated in that way? Discuss their findings and ideas. Using your previous observations, in what order will the rocks be separated if we shake this jar? Shake the large jar of rocks, and compare their predictions with the results. 

    Concept Introduction Phase:
    Explain that scientists have names for the different sizes of rocks that they sort. Introduce and discuss the following words: pebbles, sand, and gravel. Show examples, write the words on the board, and check for understanding. Draw a sample cup on the board and have the students explain how the layers will separate. Have the students go back to their work areas and draw the result in the result area of their prediction sheets. Make sure each student labels the prediction sheet with the rock vocabulary learned above. 

    Concept Application:
    Introduce a container of three different sized objects (small beads, large beads, large marbles). Have the students draw and label what they think will happen if the container is shaken (using the other side of the prediction sheet). Shake the jar, and have students draw the results. Students may discuss the outcome with their peers. Assessment: The students’ second prediction (with the objects) will be assessed to see if they understood the sorting concept. The following criteria can be used (out of 5 possible points):

    • 1 point – Layers are present.
    • 1 point – The largest objects are drawn on the top layer.
    • 1 point – The mid-sized objects are drawn in the middle.
    • 1 point – The smallest objects are drawn on the bottom.
    • 1 point – The picture is labeled.

    Useful Internet Resource:
    * National Science Education Standards
    Contains the full-text of the National Science Education Standards.