Diving into Density

Learning Resource Type

Lesson Plan

Subject Area

Science

Grade(s)

5

Overview

This inquiry-based lesson provides an introduction to density allowing students to explore density and its relation to objects floating and sinking. 

This lesson results from a collaboration between the Alabama State Department of Education and ASTA.

Science (2015) Grade(s): 5

SC15.5.5

Construct explanations from observations to determine how the density of an object affects whether the object sinks or floats when placed in a liquid.

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Vocabulary

  • density
  • volume
  • buoyancy
  • data
  • observe
  • explain
  • sink
  • float
  • mass

Knowledge

Students know:
  • Objects are made of many tiny particles to small to be seen.
  • Some objects have many tiny particles compacted close together that causes the object to sink while other objects the same size may float because their tiny particles are less compact.
  • Some objects of the same size sink when others float.
  • Buoyancy is the ability of an object to float.

Skills

Students are able to:
  • Predict the results of different types of objects being placed in water. Test the objects and communicate the results.
  • Use appropriate tools (Scale, balance, ruler, or graduated cylinder) to measure the weight, mass, and/volume of an object.
  • Construct an explanation to describe the observed relationship between density and the ability of an object to sink or float.
  • Identify the evidence that supports the explanation that density affects the ability of an object to sink or float.

Understanding

Students understand that:
  • Cause and effect relationships are routinely identified and used to explain phenomenon like sinking and floating.

Scientific and Engineering Practices

Constructing Explanations and Designing Solutions

Crosscutting Concepts

Cause and Effect

Primary Learning Objectives

The student will:

  • predict the results of different types of objects being placed in water, test the objects, and communicate the results.
  • construct an explanation to describe the observed relationship between density and the ability of an object to sink or float.
  • identify the evidence that supports the explanation that density affects the ability of an object to sink or float. 

Additional Learning Objective(s)

Scientific and Engineering Practices:

  • Students will be able to construct explanations and design solutions.

Crosscutting concepts:

  • Cause and Effect

Procedures/Activities

ENGAGE: As an introduction to density, students will observe a golf ball that is suspended between a layer of salt water and fresh water and discuss possible explanations for how this is happening.

What is the teacher doing?

What are the students doing?

Probing Questions/

Possible Misconceptions

PRESENT THE GOLF BALL SETUP TO THE STUDENTS:

  1. Use science notebook or notebook paper.
  2. Remind students to record only what they can observe rather than trying to explain why this is happening.
  3. Once students have had a chance to observe and sketch for 3-5 minutes, have them turn and talk to a partner and discuss what could cause the golf ball to be suspended in the container of liquid.

 

 

  1. Students should observe and sketch the setup and record their observations on their lab sheets.
  2. Students should discuss with a partner what they think could cause the golf ball to be suspended in the liquid.

 

 

  1. What do you see?
  2. How can you describe this so that someone else would understand what you are seeing? (Visually-impaired students should be partnered with a seeing peer that can describe what they are seeing verbally.)
  3. (If a student refers to “water”) What makes you think it is water? What led you to believe that? Could it be anything other than water?

 

SAFETY CONSIDERATIONS: Because students will not be handling the materials, there should not be any safety concerns that are beyond the usual classroom procedures and routines.

EXPLORE: After writing a hypothesis, students will use the given materials to attempt to suspend the golf ball in the liquid.

What is the teacher doing?

What are the students doing?

Probing Questions/

Possible Misconceptions
  1. Divide the students into pairs or groups.
  2. Give each group all the materials (container half-filled with water, salt, and the golf ball) and instruct them to write a hypothesis explaining how the golf ball can be suspended in liquid using these materials.
  3. Instruct students test their hypotheses by using the materials to try and suspend the golf ball halfway in the liquid.

 

 

  1. Each pair or group should write a hypothesis explaining how the golf ball can be suspended in the liquid using these materials.
  2. Each pair or group should work together to test their hypothesis.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SAFETY CONSIDERATIONS: Students should wear goggles and be reminded to keep the salt and salt water away from their eyes. Be aware of spills on the floor and have paper towels available for cleanup.

EXPLAIN: Students will report their hypotheses and explain whether they were proven or disproven and why. The teacher will discuss density and the role that it plays in the floating and sinking of objects.

What is the teacher doing?

What are the students doing?

Probing Questions/

Possible Misconceptions
  1. After the groups are successful, discuss density and why the golf balls are floating at that particular location. Add a few drops of food coloring and gently stir to show them that the fresh water is less dense and is actually sitting on top of the more dense salt water. If time allows, have groups add food coloring to their containers.
  2. Remove the containers from desks/tables.
  3. Provide the definition for density: Density is the relationship between the mass of the substance and how much space it takes up.
  4. Explain that we can actually calculate the density of an object using the formula: d=m/v.
  1. Students should report their hypotheses and then explain why their hypotheses were proven or disproven. This should also be recorded on the lab sheet.
  2. Students should take an active role in the discussion of what they observed and why they think the golf ball is suspended.

 

  1. Students should record the definition for density on the lab sheet.

 

 

  1. Students should record the formula for density on the lab sheet so that it is available for them. 

 

Probing Questions:

  1. How did you use the salt?
  2. What difference did the salt make?
  3. Why do you think the salt made a difference?
  4. Do you think this would work with any other liquids? Why?

 

 

Possible Misconception:

 

Students may have the misconception that the golf ball is floating due to a perfect salt concentration in the saltwater solution. Be sure that they understand that the golf ball is suspended at the point where the fresh-water and saltwater meet. It is sitting on the saltwater because it is more dense and sinking through the fresh water because it is less dense.

SAFETY CONSIDERATIONS: Students should not be working with materials at this time, but because goggles are removed, remind them to keep salt and salt water away from eyes and avoid having their hands around their faces. Be aware of spills on the floor and have paper towels available for cleanup.

If continuing on another day, this is a logical place to split the lesson. Be sure to review your EXPLAIN before moving into ELABORATION.

ELABORATION: Students will apply what they have learned about density, including the definition and the formula, to determine whether objects will sink or float.

What is the teacher doing?

What are the students doing?

Probing Questions/

Possible Misconceptions
  1. Prepare two large clear storage containers by filling them halfway with water. Having two containers will save time during testing students’ predictions.
  2. Write the words density, mass, and volume on the board or chart paper. Define these and discuss the difference between density, mass, and volume. You may bring students up to role play “more dense” and “less dense” by having them stand together in a group and move closer together or farther apart.
  3. Show the students a regular and a diet soda of the same type. Ask them how they could determine if the sodas would sink when placed in water.
  4. Instruct students to work with their groups to formulate a plan for making an accurate prediction. Check with them to determine if they are on the right track. Students should be applying what they have learned about mass, volume, and density.
  5. Once students have written a plan, made calculations and predicted what they believe will happen to each can, have them test their predictions using the clear plastic containers of water.

 

NOTE: The regular soda sinks because it is more dense as a result of the sugar content.
  1. Students should record the definitions for mass and volume on the lab sheet along with the definition of density.

 

 

  1. Have students demonstrate density using role play.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  1. Have students work with their groups to design a plan to determine which can will float and which can will sink before they ever place them in the water.

 

 

 

 

  1. Groups should place their cans into the containers of water to test their predictions. They should do this so that no one else can see the results. Be sure air bubbles are not trapped beneath the can. 
  2. After testing the cans, each student should explain the reason for their prediction being correct or incorrect.
  3. What is the difference between mass, volume, and density?
  4. How could you use what you know about mass, volume, and density to determine which soda can will float and which will sink before testing them in the water?
  5. Were your calculations correct? Did your calculations allow you to make an accurate prediction?

 

 

 

SAFETY CONSIDERATIONS: Be aware of spills on the floor and have paper towels available for cleanup.

EVALUATION: Evaluation should be ongoing throughout the lesson, but after the ELABORATE, the teacher will assess the student’s level of understanding by reviewing the lab sheets and assessing each student’s explanation of why his/her prediction was correct or incorrect.

What is the teacher doing?

What are the students doing?

Probing Questions/

Possible Misconceptions
  1. Circulate during group work to be sure that everyone is engaged in the work.
  2. Review each student’s explanation of their procedures for making his/her prediction, the results, and the explanation of the findings.

NOTE: Student predictions do not have to be correct, but they should be able to clearly explain why they are correct or incorrect.
  1. Students should clearly describe their procedure for calculating the density of the sodas in order to make a prediction about the sinking or floating of each can.
  2. Was your prediction correct or incorrect? If incorrect, why?
  3. How did you determine mass?
  4. How did you determine volume?
  5. How did you calculate density?

 

 

SAFETY CONSIDERATIONS: Be aware of spills on the floor and have paper towels available for cleanup.

Assessment Strategies

Because this is an introductory lesson, the focus should be on formative assessment to help inform instruction. 

Example of formative assessment to be given after the lesson:

Please write one paragraph explaining the relationship between density and the ability of an object to sink or float. Use evidence from the investigations to support the explanation that density affects the ability of an object to sink or float. 

Applied vocabulary should include: mass, volume, density, sink, float.

Acceleration

Provide students with a variety of objects that they could test using the procedures from the Elaboration portion of the lesson. (wood block, nail, lemon, lime, paper clip, etc.). 

Intervention

For ELLs:

It may be helpful to preview the vocabulary that will come up in the lesson. Providing the terms on cards would help them to visualize the word as they hear you say it during the lesson.  (mass, volume, density, sink, float)

For struggling writers:

Allow struggling writers to use sketches and a verbal explanation if writing a paragraph presents a barrier to determining their level of understanding.

Total Duration

91 to 120 Minutes

Background/Preparation

Prior to the lesson, students will need to be familiar with volume and how to find the volume of a substance or object. They will also need to be familiar with how to use a balance to find the gravitational mass of an object. 

BEFORE STUDENTS ARRIVE:

  • Golf Ball Setup:

Fill container ½ full of tap water. Add salt until no more salt dissolves. Add golf ball to the salt solution (it should float!). Gently add fresh water on top of the salt water solution.

Materials and Resources

Clear plastic container (approx. 3-5 L for golf ball setup) (one for demo and one for each group)

Kosher (pickling salt) salt

Golf ball (one for demo and one for each group)

Food coloring

Water

2 Clear plastic containers per group(Large storage container size for soft drink can setup)

3 Different types of soft drinks in diet and regular per group (ex. Coke and Diet Coke, Sprite and Diet Sprite, Sunkist and Diet Sunkist)

Paper towels

Balance for finding mass

Goggles

Approved Date

2016-04-19
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