• Life in the estuary relies on water circulation to replenish nutrients and oxygen.
• Solutions with less density float on solutions, which are denser.
• Molecular concentration and water temperature both affect density.
• Students will be using science notebooks. To learn more, go to: http://www.sciencenotebooks.org
• This lesson is also available in PDF. Click here to download.

• Does fresh water float on salt water?
• Does warm water float on cold water?
• Does a change in temperature or density affect water circulation?

1.1.1 Properties of Substances
Understand how to use physical and chemical properties to sort and identify substances. W
(6) Identify, categorize, describe, and sort substances using physical and/or chemical properties (i.e., boiling point, density, freezing point, mass, acidity (pH), solubility, magnetism).

1.1.4 Forms of Energy Understand that energy is a property of matter, objects, and systems and comes in many forms (i.e., heat [thermal] energy, sound energy, light energy, electrical energy, kinetic energy, potential energy, and chemical energy). W
(6) Describe the forms of energy present in matter, objects, and systems (i.e., heat [thermal] energy, sound energy, light energy, electrical energy, kinetic energy, potential energy, and chemical energy).

1.2.3 Structure of Matter Know that substances are made of small particles. W

Understand that all matter is made of particles called atoms and that atoms may combine to form molecules and that atoms and molecules can form mixtures. W (6) Know that matter is made of particles called atoms and molecules. (6) Know that elements are made of one kind of atom.

• It is only wave and tide action that moves water in the estuary.
• Temperature has no effect on density.
• All water in an estuary is salt water and is the same as the ocean.

• This set of lessons can be done over 3-5 days. Do one investigation a day and the lab report can be done in class or as homework depending on your time and if the class needs more guided practice in report writing.
• This set of lessons can be an extension of the Foss Mixtures and Solutions kit or other lessons where the students have explored saturation, concentration and density and know how to prepare solutions and conduct experiments.
• The students will record their observations and thoughts in their science notebook. Students should complete at least one complete lab report.
• Journals and lab reports will have been used in the past or will have to be modeled for the students in this group of lessons.

• This lesson focuses on how the physical properties of water, in an estuary, contribute water circulation.

• Important structures:
• Water molecules
• Sodium Chloride
• Sun
• Energy Transfers:
• Sunlight to heat in water

• Notebooks
• Lab reports students select which experiment they wish to turn in.
• Participation in lab activity
• Written test

Day 1: Temperature investigation
Preparation ahead:  Make dark colored ice cubes, 1 for each group.

1. Ask the students if temperature affects water density?  Have the students discuss as a small group what they think will happen when warm and cold water are mixed.  Have them record their ideas in their notebooks or on a small white board.
2. Have the groups state their hypothesis (prediction) and work with the class to design an experiment to test what will happen. Each group should have their own clear container to use during the investigation.
3. Have the students do each part of the investigation and draw what they see in their notebook for each part.  There should be a series of drawings over time showing changes.  Tell them that these drawings are their observational data and they need to be neat, labeled and colors shown.
4. After the experiment is finished they need to record the findings in their notebook.  They may choose to write this lab as their assignment. Remind them that they are responsible for one complete lab report at the end of the week.  The conclusion should include how these findings apply to the estuary water circulation.

• Experiment adapted from Science Learning Network – link to page in resources section below.

• Clear glass bowl or container for each group
• Blue or other dark food coloring for ice cubes
• Red food color for hot water
• Freezer and ice cube trays – each group will need at least 1 cube
• Room temperature water
• Thermometer
• Hot water at least 110 degrees F (43C) – microwave or an electric teakettle works well if the faucet water is not hot enough.
• Styrofoam cups

Procedure: Part 1

1. Fill the glass container to the top with room temperature water and let it sit until it is still.  Try not to bump the tables or bowl.
2. Each group will get 1 dark ice cube and place it gently into the water in the clear container.
3. The students should observe and record what they see every 10 seconds until the ice has melted. They need to be careful not to disturb the container or bump the table.
4. They should take turns drawing and then at the end each of them copy the observations into their notebook.

Procedure for part 2:

1. Start with a fresh bowl of room temperature water. Let it sit until still.
2. Give each group a small amount (2-3oz) of the hot water with enough red dye to make it dark.
3. Have the students gently pour the hot water into the container.
4. The students should observe and record what they see every 10 seconds until the water stops moving. They need to be careful not to disturb the container or bump the table.
5. They should take turns drawing and then at the end each of them copy the observations into their notebook.

Day 2

1. Review what was observed on day one. Ask for their ideas on how this applies to water in nature.  How do the seasons affect water movement?
2. Do the saline investigation following day one’s routine including notebook and lab writing.
3. Use the link as a guide for an investigation in salinity changing density.

• Experiment adapted from Science Learning Network – link to page in resources section below.

• Room temperature water
• Clear container for each group
• Green food coloring
• Salt
• Measuring spoons
• Small cup

Procedure:

1. Fill container with fresh water
2. Mix 5cc salt with 100cc water into the cup mix well
3. Add green food coloring until dark green
4. Have the students gently pour the salt water into the container.
5. The students should observe and record what they see every 10 seconds until the water stops moving. They need to be careful not to disturb the container or bump the table.
6. They should take turns drawing and then at the end each of them copy the observations into their notebook.
7. Just add the correct proportion of tap water to get different concentrations if you want to extend this lesson. So add 3.5cc of the saline solution to 100cc of tap water for approximate ocean salinity and 2.5 cc to 100cc for estuary salinity.  You can have the students mix their own solutions.  Have them try the different concentrations. Have them try mixing the 3.5cc/100 and 2.5cc/100, color one of the solutions.  What happens? Is the density difference enough for layering now?

Day 3

1. Review the findings from day 2. Ask if any of the students have been swimming in salt water.  What did they notice compared to swimming in fresh?
2. Have the students in their small groups design an experiment to test if an egg will float in water including all parts of the design from question to blank data table. This should be written in their notebooks.
3. Have each group share what they will do and conduct the experiments on day 4.

Day 4

Materials:

• Lab Report Forms http://www.padillabay.gov/lessons/LabForm.pdf
• Raw eggs
• Salt
• Water
• Containers

1. Have students do their egg floating experiments.
2. When done have the students share their results.
3. Have them start their lab reports in class.  Have them include how the increased buoyancy of salt water would be an advantage to estuary life in their conclusions.

Day 5

Assessment activities

• Peer or teacher notebook review
• Essay response on the question, How does density affect the water circulation in an estuary? How does the life in the estuary benefit by this water movement?
• Lab report reviews. – See attached lab report form.

This is the web site that has the temperature procedures for this lesson.
Water on the Move Current EventsWater on the Move Current Events
http://www.mos.org/oceans/motion/density.html

This is the link for the egg floating procedures.
http://www.chem.umn.edu/outreach/Card-FloatEgg.html

The geography section of the Chem4 kids site is another great resource for science information for this unit.
http://www.geography4kids.com/files/water_seawater.html

For any science Here is the Chem4kids home page.
http://www.chem4kids.com/index.html

The Fermi lab site has wonderful science resources.
JHU/APL Ocean Currents Web Site
http://fermi.jhuapl.edu/student/currents/index.html

Foss science kits homepage
http://www.fossweb.com/modules3-6/

NASA site that has a great graphic on tidal mixing.
http://earthobservatory.nasa.gov/Study/LovelyDarkDeep/

Another NASA site that has great oceanography information

http://podaac.jpl.nasa.gov/