Sink or Float? Inquiry Investigation

Anne Gardner, Bruce F. Vento Elementary, St. Paul, MN based on an activity from Science NetLinks
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Students will predict which objects sink or float in water. They will observe, describe, and keep records about what happens when objects are placed in water, and determine whether there is consistency in their own and classmates' results. They will generate ideas about characteristics of materials that sink or float, and will ask questions about physical properties of matter.

Learning Goals

Students will make and test predictions about sinking and floating. They will classify objects according to physical properties. Students will develop process skills in observing, questioning, predicting, interpreting, and communicating.

1. Objects made of wood will usually float.
2. Objects made of metal will usually sink.
3. Heavier objects tend to sink; weight is a factor in whether objects float or sink.
4. We expect to get a similar result when a science investigation is repeated.


Context for Use

Suitable for K-2nd grade students working in the classroom; could also be done outdoors for easy clean up. Class size of 18 is ideal for forming groups of 3 students. A 60 minute block is needed. Students should know how to take turns and work in a small group.

-Small tub ½ full of water
-5 different items that are made from various materials
--aluminum foil
--plastic bottles
--plastic forks
--sponges (etc.)

For younger children, you may want to give each group the same set of 5 objects to focus their discussion and their ideas. Teacher needs a large clear tub ½ filled with water and a similar variety of objects as well as chart paper and markers. A Sink or Float Activity Sheet (please change the word Guess to Prediction before you copy) and Assessment Sheet for each child; find these at the Science NetLinks website listed in the Teaching Notes section below.

Subject: Chemistry:General Chemistry:Properties of Matter
Resource Type: Activities:Classroom Activity
Grade Level: Primary (K-2)

Description and Teaching Materials

On the chart paper, prepare a chart with the title "Sink or Float?" and 4 columns labeled: Object, Prediction, 1st try, and 2nd try.
Set the large tub of water in front of the class and have students gather around the tub. Discuss experiences they have had with water; introduce the words sink and float and check for their understanding by having them tell about things they have seen floating or sinking (toys in the bathtub; boats on the river; rocks in a lake; themselves in the swimming pool; diving rings in the swimming pool). Show one of the objects; pass it around and have each student make an observation about it. Sketch the object and/or write its name in the first column on the class chart. Point to the word Prediction in the next column and remind students that a prediction is not a guess but is an idea about what will happen next, based on something we have already seen or know about. Model predicting whether the first object will sink or float, using words and reasoning that you want your kids to learn and use: "I predict the rubber ball will float because I know a rubber duck will float in the bathtub." Write your prediction "Sink" or "Float" in the second column. Place the object in the water and observe what happens. Record the result in the 3rd column. Discuss with students whether your prediction was the same as or different from the result. Avoid using the words right and wrong so that students do not judge their predictions in those terms. Explain that scientists need to know if what they observe can happen more than once, so that we will be repeating the procedure with each item we test today. Repeat the procedure with the same item and record the result in the 4th column. Choose another item and repeat the demonstration of this process of observing, predicting, investigating using 2 trials, and recording the prediction and outcomes.
Give each child a copy of the Activity Sheet. Put students in small groups and give each group a small tub of water and 5 items to test. For each item, have students complete on their own sheet:
1. Draw or write the name of the item in column 1. (For younger children, you may want to do this before you make copies of the sheet.)
2. Predict whether it will sink or float and record their prediction in column 2. Each child should tell their group why they made the prediction.
3. Students place the item in the water and observe what happens. Record results in column 3.
4. Repeat the procedure and record the results in column 4.
When groups are done testing their objects, have the whole class sort the items into a Float pile and a Sink pile. As a class, discuss their results and their observations. Guide them to notice how often their prediction matched their results. Describe the objects in the Float pile and the Sink pile-do the items in each pile have anything in common with the other objects in that pile? Discuss similarities and differences in the material characteristics that might affect whether objects sink or float. Write their ideas on chart paper. These ideas may inspire their questions, such as Does weight affect sinking and floating? Does the depth or amount of water matter? Can I change a Floater into a Sinker? Or a Sinker into a Floater? Students could be given time another day to plan how they would answer one of these questions and carry out their plan.

Teaching Notes and Tips

This is a pretty straightforward activity, which I have adapted from a lesson plan on the AAAS Science NetLinks website at: The files for the two sheets are located at this link. I have not done this activity but I have worked with grades K, 1, and 2 in the past and could picture all of my students being engaged and having success as it provides a lot of modeling to scaffold their thinking and learning. The Everyday Math sink & float activity for Kindergarten could be modified using this activity.
To use this as an inquiry based investigation, I made suggestions as I described the activity: e.g., use language that you want kids to know, and expect them to use it; change the word "Guess" to "Prediction" in the Activity Sheet to more accurately reflect what children are doing.


After the class has generated its list of ideas about the properties of materials that sink or float, bring out a group of toys that can be placed in water and that the students have not tested for sinking or floating. The toys should be made of the same materials that you tested (wood, plastic, metal, etc.) that the class has generated some ideas about. Show one toy at a time and ask students to predict whether it will sink or float; have them draw their predictions on the Assessment Sheet. If time allows, have students tell why they made that prediction, using the language you have modeled.


General Scientific Inquiry standards for grades K-2
Specific standards for Grade 1:
1.I.B.1-questioning, observing, and seeking answers 1.II.A.1-describing physical properties

References and Resources