Cleaning Water: A 5th Grade Standards-Based Science Unit

Author(s): (Coach) David Mann, (Team Members) Kevin Baldizon, Jeff Foote, Robin Schneider, Ben Wieman

Lesson Overview

Grade level(s):

Elementary School (K-5), Grade 5, Grade 6

Subjects(s):

Chemistry, Earth Science, Engineering, Science Skills

Topic:

Chemistry, removal of water pollution materials, physical and chemical properties

Big ideas(s):

Water is everyone's first need. How do we ensure that our water is safe to drink?

Vocabulary words:

Filtrate

Filter paper

Observations

Properties

Color

Clarity

Solids

Density

Distillation

Odor

Volume

What you need:

If the school does not have laboratory equipment, an inexpensive funnel device can be made from a plastic drinking bottle.  Half of the bottle can be made into a funnel and the other half as a cup for catching the water filtrate.  The device can be made as follows:

A 500 mL water bottle cut in half using a hacksaw or sharp knife, (teacher assist students or prepare bottles ahead of time).

Drill a 7/16 “ hole in the cap and screw in a ¼ “ fitting with a barbed hose end.  Place 5/8” O.D. O-ring on it and attach 3” of ¼” latex tubing.  All materials found at the hardware store for a total cost of $3.00 (see the attached PDFs for images of materials needed and assembly)

One gallon of  "Foul" water can be make with the following:

2/3 cup of used coffee grounds
1 teaspoon garlic powder
1/2 cup of vegetable oil
1 tablespoon of sodium chloride (table salt)

You will also need the following:
1/2 inch rocks, 1/4 inch Gravel, and pre washed sand
Filter paper
Charcoal
Conductivity meter

(see the attached PDF to see the materials needed and assembly)

Grouping:

Students should work as pairs.

Setting:

This lesson is done in the regular classroom.

Time needed:

Required 30-45 min. as teacher demo. Or… 3-4 days as class activity.

Author Name(s): 
(Coach) David Mann, (Team Members) Kevin Baldizon, Jeff Foote, Robin Schneider, Ben Wieman
Summary: 

Many children around the world die due to drinking contaminated water.  This engaging science lesson will allow students learn how to build and use a simple homemade filter system to clean contaminated water. This 5th grade, standards-based lesson is great for California Science Content Standards Earth Sciences.  Students make observations, collect data and form hypothesis.  The end result is a gratifying surprise that they will enjoy while learning basic investigation and experimentation concepts.

Prerequisites for students: 

None

Learning goals/objectives for students: 

The learning goal for the lesson is that students will become more aware of the need for clean drinking water. (slide show on poor water conditions for children: http://www.sohip.org/slideshow/html/2.htm)

The objectives for the lesson are as follows:

1.  Students will be able to construct a water filter using a plastic water bottle.

2.  Students will be able to answer correctly all the pre/post lesson questions.

3.  Students filtered water sample will be free of oil, solids and odor.

Content background for instructor: 

Though covered with water, only 3% of earth's water is fresh water, and 99.7% of earth's water is not available for use by humankind. (http://www.usgs.gov/)

This leaves less than 1% of all the world's water for all of civilization.

One of every six people on earth lack clean, fresh water.

We can help!

The United Nations has named 2005 - 2015 the decade of fresh water.

By 2025, some 60% of humanity will live in water-scarce, urban settings (www.un.org)

More information on clean water issues can be found at the United Nations Development Programme (http://www.undp.org/water/)

Getting ready: 

1) Create inexpensive funnels, using plastic drinking bottles (need one per pair):

Take a 500 mL water bottle cut in half using a hacksaw or sharp knife, (teacher assist students or prepare bottles ahead of time).

Drill a 7/16 inch hole in the cap and screw in a ¼ inch fitting with a barbed hose end.  Place 5/8inch O.D. O-ring on it and attach 3 inch of ¼ inch latex tubing.  All materials found at the hardware store for a total cost of $3.00. See attachments for photos.

2) Prepare the gallon of "foul" water ahead of time (see the "What you need" section for ingredients)

Recipe for the Foul Water:

An easy recipe for the foul water is to place 400 mL of tap water in a 500 mL flask (or another empty water bottle or 5 gallon bucket) along with 1 tsp. of sifted coffee grounds, 1 tsp. of sifted garlic powder and 25 mL of vegetable oil and 1tsp of sodium chloride (table salt). Stopper and shake. The mixture tends to separate out; it is therefore important to shake the foul water sample just before giving it to students. To ensure a more or less consistent mixture sample for each student group, continue to keep the foul water shaken up. If you have one, another way to keep the mixture well stirred is to place it in a large beaker on a stir plate, and draw out samples while it is stirring using a plastic pipet.

Lesson Implementation / Outline

Introduction: 

Show the attached PowerPoint slides to generate discussion on how water could be polluted and what could happen from drinking dirty water.

Activity: 

The following can be handed out in a student version with procedures to follow (see attached):

Have students prepare a data table like the one below.

  What  Color is the water? (Describe) Clarity Can you see through the water? (yes/no)

Odor

Does the water smell? (yes/no)

Oil Is oil floating on top of the water? (yes/no)

Solids Are there chunks in the water? (yes/no)

Volume

How much water do you have?

Before Treatment            
After Oil - water separation            
After sand filtration            
After charcoal treatment            

 

Procedures: (before you begin treating the foul water, have students record their observations BEFORE they do anything to it)

1.  Have students obtain approximately 100 mL of foul water, provided by the teacher.  Have them measure its volume with a graduated cylinder; and record the amount in their data table.

2.  Have students examine the properties of their sample: color, odor, clarity, and presence of solids and/or oily regions.  Students should record their observations in the "Before Treatment" section of their data table.

Oil - Water Separation (The separation is similar to some large scale water purification methods).

Oil and water do not mix (this is because of their chemical composition, water is a polar substance and oil is non-polar, oil and water also have different densities, oil is less dense than water to it float on top of the water).

1)  Students should allow the water to settle for a few minutes.  Two layers should form -- with the oil floating on top of the water.  Additionally, large solid particles should sink to the bottom and oil droplets along with some low density solids float to the top and form a scum layer on top. The top layer of oil and scum can be separated out by using the funnel device you made or an actual funnel and a piece of rubber hose.

2)  Students should pour their water into their filter while squeezing the rubber tube closed, allowing the oil to float to the top.  Then they should carefully let the water drip into their collection cup. When the lower layer has drained out, quickly close the rubber tube. The top oily layer is discarded down the drain. The water obtained from this technique is considerably "cleaner" than it was to begin with, but it is still somewhat cloudy and smelly!

3) Observe the properties of the remaining layer and measure its volume. Record your observations and data. Save the water for the next procedure.

4) Wash the funnel with soap and water.

5) Record your observations in your data table.

(This can also be done as a teacher demo).

Sand Filtration

Next,  the student s will pour the foul water sample through the paper cup sand filter, which traps solid impurities that are too large to fit between sand grains.

Procedure

1. Using a straightened paper clip, poke small holes in the bottom of a paper cup.

2. Add pre-moistened gravel and sand layers to the cup (with 1cm gravel on the bottom, 2cm sand next and 1 cm gravel on top of the sand). The bottom gravel prevents the sand from washing through the holes. The top gravel keeps the sand from churning up when the sample is poured in.

3. Gently pour the sample to be filtered into the cup. Catch the filtrate (filtered water) in a beaker as it drains through.

4. Dispose of the sand and gravel into a waste bucket.

5. Observe the properties and measure the volume of the water. Record your results. Save the water sample for the next procedure. After the sand filtration, the sample is much clearer, although it might be slightly colored, and it still has the stench of garlic.

Charcoal Adsorption/Filtration

Charcoal adsorbs (attracts and holds on its surface) many substances that could give water a bad taste, odor, or cloudy appearance. After the charcoal filtration, the sample is generally a clear, colorless, and more or less odorless liquid.

Procedure

1. Fold a piece of round filter paper (first in half, then into quarters)

2. Place the folded filter paper in a funnel (so it opens up in a cone shape). Wet the paper slightly so it adheres to the funnel cone.

3. Place the funnel in a clay triangle supported by a ring clamp. Lower the ring clamp so the funnel stem extends 23 cm inside a 150mL beaker.

4. Place one teaspoon of charcoal in a 125or 250mL Erlenmeyer flask.

5. Pour the water sample into the flask, put a rubber stopper on top and shake vigorously. Then gently pour the liquid through the filter paper. Keep the liquid level below the top of the filter paper, no liquid should flow between the filter paper and the funnel.

6. If the filtrate is darkened by small charcoal particles, re-filter the liquid. Use a clean piece of moistened filter paper.

7. When you are satisfied with the appearance and odor of your purified water sample, pour it into a graduated cylinder.

Observe and record the properties and the final volume of the sample.

Each step involves some loss of water, and the final purified sample might only have about one fourth the volume that the original sample has.

Detection of Invisible Material (Salt)

This purification does not remove soluble ionic salts. The salts do not adsorb on the surface of the charcoal particles. The presence of the invisible material (table salt) can be detected with a simple conductivity meter.

Pocket Conductivity Meters

Point out to the students that just because the water looks clean does not mean that the water really is clean! Stress that there is still something in the water that they cannot see. Then demonstrate using the conductivity meter. A beep or light coming on is a positive test for the presence of an unseen material.

Distillation of water
Boil the filtrate in the Erlenmeyer flask using a stopper and glass tube and a piece of rubber tubing to collect the vapors. Retest the
distillate to see if it still conducts electricity.

Checking for student understanding: 

The following is a pre/post test for the activity:

Pre/Post Water Activity Test

1.    Where does clean drinking water come from?

2.    How would you remove or separate oil and water?

3.    What property of matter allows the separation of oil and water?

4.    If water looks clean can you assume it is clean?  Why or why not?

5.    How can you get rid of the smell in dirty water?

6.    If distillation is a way to really make clean water, why don’t we use it more often?


Pre/Post Water Activity Test Teacher Answer Key

1.    Where does clean drinking water come from?
Clean water may come from:
•    The ground
•    Rivers
•    Streams
•    Lakes
•    Rain
However, to make sure the water is safe to drink, one should boil the water before drinking.

2.    How would you remove or separate oil and water?

Because oil and water do not mix, you can separate them by letting the oil float to the top and then skim it off.

3.    What property of matter allows the separation of oil and water?

Density

4.    If water looks clean can you assume it is clean?  Why or why not?

No!  Because small things could be in the water

5.    How can you get rid of the smell in dirty water?

Charcoal is added to the water

6.    If distillation is a way to really make clean water, why don’t we use it more often?

Because it is expensive.

Wrap-up / Closure: 

The wrap-up can be done with a variety of assignments:

Post water activity quiz

1.  Have the students take a post activity quiz

2.  Have the students make a log of places in their home where water use could be cut back or water used more than once.

3.  Have students take a field trip to the local water treatment plant.

Extensions and Reflections

Extensions and connections: 

1.  Have the students make a log of places in their home where water use could be cut back or water used more than once.

2.  Have students take a field trip to the local water treatment plant.

3.  Have students explore where their local water comes from, and where it goes after they use it.

AttachmentSize
Elem. Curriculum.ppt9.95 MB
NSTA Presentation.pdf13.03 MB
Teacher Transparencies.ppt5.38 MB
elementary Sand Filter Curriculum 2.pdf1.01 MB
Funnel Assembly and Gravel Set Up smaller.pdf10.34 MB
NGSS Topics
Kindergarten through Grade 5: 
Engineering, Technology and Applications of Science: 
NGSS Disciplinary Core Ideas
NGSS Performance Expectations
NGSS Performance Expectations: 
5-ESS3-1
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
NGSS Crosscutting Concepts: 

Standards - Grade 5

Earth Sciences: 
3. Water on Earth moves between the oceans and land through the processes of evaporation and condensation. As a basis for understanding this concept:
a. Students know most of Earth's water is present as salt water in the oceans, which cover most of Earth's surface.
b. Students know when liquid water evaporates, it turns into water vapor in the air and can reappear as a liquid when cooled or as a solid if cooled below the freezing point of water.
c. Students know water vapor in the air moves from one place to another and can form fog or clouds, which are tiny droplets of water or ice, and can fall to Earth as rain, hail, sleet, or snow.
d. Students know that the amount of fresh water located in rivers, lakes, under-ground sources, and glaciers is limited and that its availability can be extended by recycling and decreasing the use of water.
e. Students know the origin of the water used by their local communities.
Investigation and Experimentation: 
6. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other three strands, students should develop their own questions and perform investigations. Students will:
b. Develop a testable question.
g. Record data by using appropriate graphic representations (including charts, graphs, and labeled diagrams) and make inferences based on those data.
h. Draw conclusions from scientific evidence and indicate whether further information is needed to support a specific conclusion.