Rocks Can Be Changed By Water

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SWBAT design an experiment to witness how rocks can be changed

Big Idea

Rocks are changed by water and by bumping into one another over time. Rocks are changed slowly by the forces of nature.

Teacher Background

Students should be gaining experience with designing experiments to test a hypothesis. In this lesson the students will be presented with a hypothesis and asked to design a way to test their hypothesis. Their work will help them to understand that some forces of nature change things slowly.


Depending on the size of your science block you may wish to do the design on the first day and the actual experiment on the second day and sort the data and draw conclusions on the third day.


For materials I provide water in a large container, sandpaper (to represent sand on the beach), other rocks of similar size, a fan, and loose sand in a bucket. When I present the materials I explain how they model things in nature.


Students will also need to collect 1 golf ball sized rock per person for the experiment.

I Can and Hypothesis

10 minutes

Today I begin the lesson by presenting the hypothesis that rocks can be changed by nature. I hold up several rocks. I say, “I bet that these rocks can be changed by nature. What do you think?” I let students give their opinions.  “I can see that we have several different opinions about whether rocks can be changed. What could we do to help us figure out if rocks can be changed? (Experiment, test it, try it..).

“Today I would like to begin by asking you to read this I Can statement with me. 'I can design an experiment to test if rocks can be changed.'  Today we will try to design an experiment to see if we can change these rocks in any way. I would like you to come to the rug and we will work together to figure out how we might change these rocks. I have some materials you can use in your experiment."

Designing the Experiment

30 minutes

Students gather on the rug and I put some materials in the center for them to look at. I ask them just to think about how these materials might help us see if rocks can be changed. “I want to explain the materials I have put out for us to use in our experiment. I have water to represent rain or a river, lake, or ocean. I have sandpaper to represent sand on the beach. I have other rocks that these rocks might bump into and I have loose sand to represent the ground. You have seen the materials and know that we want to see if rocks can be changed, now let’s think about how we might do this.”  I want students to begin here to design the experiment. I will help them organize it into the steps of an experiment, but to reinforce the NGSS standards, I want them to do the designing. In order to allow each student to participate in the design I tell them that I am going to pass around a talking ball (a small soft ball) Using The Talking Ball and when they ball comes to them they can add an idea, or say why they like someone else’s idea.  I do this to encourage students to take part in meaningful scientific discourse. I make sure that everyone gets the ball at least once so that everyone contributes to the discussion in some way.  I say, “who would like to begin?”

Students take turns sharing their ideas or supporting the ideas of others. I record the ideas on the easel on chart paper so that we can cut the ideas apart and put them in the best order for completing our scientific experiment.  I am hoping that students suggest testing the rocks using the different materials, that they suggest that we collect data in some way about what we find and that they suggest that we draw a conclusion about our findings. If they do not suggest those things, I try to build upon what students have said in order to bring out these parts of the experiment.

When everyone has had a turn to speak I say, “we have collected some good ideas and now we need to put them in order to finish our experimental design.  What do you think we would do first?” I let students read through our ideas and suggest the order of our experiment. We will end up with several centers where students can go and test their rocks. The first step will be for them to carefully look at the rock they have chosen and sketch it in their journals. Next they will visit the centers and try sandpaper on the rock, try banging it with other rocks (wearing safety glasses), try rubbing the rock in the sand and rolling the rock in the water. For each one they will record what they notice.  

Conducting the Experiment

40 minutes

The students have designed the experiment together and now they will complete the steps and record their findings in their science journals.  They begin by predicting what will happen to the rocks in the water, when they are dropped on one another or banged together, and when they are rubbed with sand paper. Student Predictions  Student Predictions Students begin by examining their own rocks with a magnifying glass. I say, “remember that scientists observe carefully and record what they see. You may do this with words, drawings or both.” I give students about 5 minutes to study their own rocks.


Before students circulate to centers we discuss scientific safety. I tell students that they need to be careful not to bang someone else with their rock. I also introduce safety glasses and explain that while they are at the rock center they will need to wear the glasses because if they bang 2 rocks together they could chip off a piece and we don’t want it to hit anyone in the eye. I also remind them that when working at the water center, they need to be careful not to spill the water where someone might slip on it.


Next I divide the class into 4 groups, 1 for sandpaper, Changes with Sandpaper1 for water, 1 for rocks Dropping Rocks and 1 for sand. I tell them they will have 10 minutes to visit the center, test their rock and record what they see. They should test their rock for at least 6 minutes at which point I will ring the bell to remind them to record their findings. They switch centers every 10 minutes. I circulate from center to center supporting students as they experiment and record their findings. I use many why and what if questions to help students think about what they are seeing.

Sorting the Data

25 minutes

Students have collected observational data about what happened to their rock at each center. I invite them now to write one or two words on each square of paper I give them to explain what happened at each center. I demonstrate using the form I have made that has the 4 centers listed.  I ask for something that students noticed at each center and take 1 suggestion for each and record it on my sheet.  I tell students, “you may have noticed different things, or not noticed anything, be sure to write what you put in your journal.” I erase mine so students are not tempted to just copy it.


When students are done I say, “I have placed 4 sheets of paper at your tables. One is labeled for each center. Would you cut apart your sheet and place your answers on the correct piece of paper. I give students about 5 minutes to complete this task.


“Now I am going to divide you into 4 groups. Each group will get all of the cards for their center. I want you to see if you can group the cards into similar results. So if you are doing water and you find 3 shiny cards, group them together on your paper. If there are 2 that say they didn’t notice anything, put them together. You will be making a graph to display what was found at each center. “ I ask for questions and then let students complete their graphs. I circulate around to help students sort their findings.


Drawing Conclusions

15 minutes

After the groups have finished I display the graphs at the front of the room. I invite one person from each group to tell us about their graph. I encourage the rest of the class to ask for questions or clarifications.


“You have taken part in the experiment and now let’s look back at our hypothesis. I said that rocks could be changed by nature. You used some things from nature and tried to change your rock. I would like you now to write in your journal about whether rocks can be changed by nature or not, and why you think so. Also think about whether the changes happen quickly or slowly outside.  Write at least 2 good sentences in your journal to explain your thinking.” I ask for any words they might need and create a word bank on the board to help students with the writing process.


I use the journal entries from during the experiment and the final conclusions to gauge student understanding of how forces of nature change rocks.