LESSON PLAN

 

Name: Kristin Vander Voord

 

Title of lesson: Density Lab

 

Length of lesson:  Approximately 50 minutes

 

Source of the lesson:

            Based on an idea from Sound Experience curriculum from the University of North Carolina Sea Grant.

 

TEKS addressed:

            Give identification number and letter and write out the TEKS.

 

I.      Overview

In a previous lecture, students will be introduced to density and what affects it.  In order to help students learn and understand the density more, this lab will allow them the opportunity to have hands on experience with the phenomenon.  Students will use clear straws to stack colored water of different salinities.

 

II.  Performance or learner outcomes

            Students will be able to:

1.  Define density and its parameters.

2.  describe how solutes affect density.

3.  Examine the effects of temperature on the density of a liquid.

3.  Relate the difference of densities of water with the ocean.

 

III. Resources, materials and supplies needed

·        Lab aprons

·        2 500-mL beakers

·        2 narrow-necked 100-mL bottles

·        2 food colorings

·        two 3in x 3in cards

·        tray or pan

·        2 1L fresh water (one at room temp and one close to boiling

·        salt

·        paper towels

·        ice cubes

IV. Supplementary materials, handouts.

·        Worksheet with procedure and questions for the lab.

             

 

Five-E Organization

Teacher Does                     Probing Questions                      Student Does       

Engage: 5-10 minutes

So we have learned about density and the equation that relates density with mass and volume.  Review the concepts they have learned in the density lecture.  If the students struggle to remember, make hints to remind them and reinforce their prior knowledge.  In the ocean there are differences in density due to the amount of salt in the water.  This is also true in the Corpus Christi Bay.  Show the students the graphic from the Texas Water Development Board.

 

      

 

Questions:

 

 

What is Density?

 

How does changing the volume change the density?

 

How does changing the mass change the density? 

     

Expected Student

Responses/Misconceptions

 

Mass divided by volume

 

 

Inversely

 

 

Directly

 

                                                   

Explore: 30 min

Water forms density-stratified layers in many places such as estuaries, deep bays, continental shelves and in most of the open ocean.   Explain to the students that they will be examining the densities of four unknown liquids.  They are to work in groups of three or four and are to follow the work sheet that is provided.  Explain that they will have 20 minutes to complete the lab and then the class will go over their results together.  Go over the work sheet and demonstrate the process to the students.  After the demonstration let the students work on the lab.  While the students are working, circle around and ask the questions listed in the next column to help maneuver their thinking.  When time is up, ask the students to share their results.  

 

 

Questions:

 

 

 

 

 

 

 

 

 

 

 

 

What happens when you put warm water on top of cold water?

 

What happens when you have salt water over the fresh water? (Do this with two small, wide mouthed bottles, Snapple bottles work well; salt water and fresh H2O will trade places and not mix, much)

 

What does it mean this mean about the densities of these liquids? 

     

Expected Student

Responses/Misconceptions

 

 

 

 

 

 

 

 

 

 

 

 

The two stay separated

 

 

 

The two mix

 

 

 

 

The ones on top have a smaller density than the ones on bottom

 

 

 

 

 

 

 

 

 

    

Explain: 5-10 min

Ask the students to explain the relationships between density and temperature and salinity.  How does this relationship help us explain what is happening in Corpus Christi Bay.  Explain that as the salinity of water increases, so does its density.  In bays like the Corpus Christi bay, where fresh water flowing from rivers meets salt water from the ocean, the fresh water tends to float above the salt water until mixed by wind or tidal currents.  How might this affect the organisms that live in the bay?  The distribution of fish that like fresh water are going to be closer to the top and the mouth of the rivers while animals like Dolphins are going to be father away from the mouth of the river.  What is the temperature in the bay like?  The closer to the surface the warmer the water.  This is because cold water is denser than warm water.  

 

 

Questions:

 

What is the relation between density, temperature, and salinity?

 

How does this relationship help explain what is happening in Corpus Christi Bay?

 

 

 

 

 

 

 

How might the different levels of salt water affect the organisms in the bay?

 

 

 

 

 

 

 

What is the temperature like in the bay?

 

 

 

 

 

 

 

Expected Student

Responses/Misconceptions

 

Fresh water is less dense than salt water and hot water is less dense than cold water.

 

In the bay, the fresh water is on top of the salt water and the cold water is on the bottom

 

 

 

 

 

 

Fresh water fish are going to be on top and closer to the mouth of the rivers.

 

 

 

 

 

 

 

The bottom of the bay is colder than the surface

 

 

 

 

 

 

                                               

Extend / Elaborate: 10-20min

If time allows have the students make more solutions of various densities and temperatures and ask them to predict what will happen when they try to stack them.  Have them test their hypothesizes.

 

      

 

Questions:

 

What will affect which solution is on top?

 

How can you guarantee that a solution will end up on the bottom?

 

Expected Student

Responses/Misconceptions

 

The temperature and the amount of salt in the water

 

 

Keep the solution as cold as possible and as salty as possible

   

  Evaluate:

Questions asked through out the lesson will serve as a tool for assessment.  The work sheet they complete while they are doing the lab will also serve are a way to check that they have understood and fulfilled the objectives.

 

 

 

      

 

Questions:

 

Refer to the questions through out the lesson.

 

Expected Student

Responses/Misconceptions

Refer to the answers through out the lesson.

 

Density Lab

Name ______________________________________________

 

Procedure

  1. On your desk are two bottle, two beakers, two , water, salt and index cards.  Mix up two solutions in the beakers with either hot/cold/room temp water and with/without salt. Label each beaker and color them different colors.
  2. Using the two solutions you made, overfill both bottles so that liquid begins to spill over the sides to remove air bubbles.  Slide the card over the bottle to be inverted without trapping air.  Press the card against the bottle as you invert it.  Air pressure will hold the card in place.
  3. Before inverting the bottle, write a prediction in Table 1 about what you think will happen when the two solutions come in contact with each other.
  4. While the bottles are in the pan, carefully align the mouths of the two bottles.  Ask a student to hold the two bottles in place while one person removes the card.  Spills occur if the bottles are misaligned or if air bubbles are in the system.
  5. Observe the interactions of the two liquids and note in Table 2 below what happens.

 

Table 1.

     Bottle 1                  Bottle 2           Prediction

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2.

     Bottle 1                  Bottle 2           Observations