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From Dirty to Clean in 15

Activity Summary

This activity teaches students about water pollution and cleaning

polluted water with filters. Oysters filter nutrients out of water and 

clean water at the same time.

Learning Objectives

Students will be able to:

• Explain the importance of clean water to living organisms.

• Explain how oysters clean water.

Guiding Question

What role do oysters play in cleaning the water of the Chesapeake Bay?

Background Information

To survive, all living things must have clean water. Unfortunately, 

people do things every day that make water dirty and unsafe. They 

pollute the water by doing things such as throwing trash on the ground 

that gets into the rivers and streams and putting chemicals on their 

yards that runs off into the sewers. Polluted water (dirty water) affects

the health of plants and animals. Very polluted water can even make 

them sick and in extreme case, cause death. Therefore, it is very 

important to prevent pollution. However, when there is pollution, 

filters can help remove some pollutants. Nature creates its own filters, 

K-12 Oysters in the Chesapeake Bay

Grade Level: 

Kindergarten

Teaching Time: 

2-20 minute sessions

Materials:

• Clear tub or basin

• Clean tap water

• Clear plastic cups (2 

per student group)

• Rubber bands (1 

per student group)

• Filtering materials 

(coffee filter, 

cheesecloth, etc.)

• “Pollutants” for 

example:

• Food coloring

• Pieces of plastic 

grocery bags

• Pencil shavings

• Foam peanuts

• Student response 

sheets 1 &2

Teacher Note:

This activity can be used 

as an introduction to how 

oysters filter the 

Chesapeake Bay.
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such as undisturbed soil, sand and oyster beds. Scientists also create filters to clean water. For 

example, a drinking water treatment plant uses sand filters. Other filters, like silt screens and straw 

bales, are used for construction sites.

Key Words

Filter – A device that separates or removes matter

Oyster – A sea creature with a rough irregular shell sometimes eaten as a delicacy that is often

farmed for food or pearls

Pollution – Something that is harmful to living things

Activity Procedure

Day 1

Engagement 

Put a clear tub of water where all the students can see it. Let students add food 

coloring, foam peanuts, pieces of plastic grocery bags and other materials to the water. 

Ask the students what they have done to the water. Guide them to understand that 

they created pollution in the water.

Exploration

Ask the students if they would like to go swimming in the polluted water they created. 

Why or why not? Then ask if they think a fish or a crab would like to swim in the water, 

why or why not? Discuss why clean water is important for them and other living things.

Day 2

Engagement

Give the students oyster shells to investigate for several minutes. Ask them to share 

what they observe, and then ask if they know what the shells are. Ask them to share 

what they know about oysters.

Exploration

1. Tell the students that it is time to clean water they polluted, and ask them how they 

would do it. Then ask how they would clean the water if they could not put anything 

into the water (hands, nets, tongs, etc.). Try the different ways they suggest (as much as 

feasible) and have them evaluate the results. Guide them to the idea of a filter. To help 

them understand, you can discuss how a fish tank filters/cleans water, how they sift 

sand in the sandbox, or how their parents keep the coffee grounds from going into the 

cup when they make coffee or keep the tea leaves out of the water when they make 

tea.

2. Scoop out several cups (one per group of students) of polluted water from the tub. 

Cover each polluted cup with one of the filtering materials, secured with a rubber band. 

Divide the students into small groups and have each group pour the polluted water into 

an empty clean cup (over the tub of water). Ask them to describe what is happening. 
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While each group is pouring the water with the teacher, the rest of the class can draw 

what the cup of polluted water looks like on the Student Response Sheet 1.

Explanation

1. Ask the class to explain what happened with they poured the polluted water through 

the filter into the clean cup. Have them describe what the cups looked like after the 

pouring and discuss what the filter did (blocked the pieces, took some of the food 

coloring out of the water, etc.). Have them draw what the cup looked like after they 

poured out the water and explain in writing, or orally, what happened and how the filter 

worked.

2. Explain that there are water filters in nature and the owners of the shells they looked at 

are very good at filtering and cleaning water. Show the students a live or shucked oyster 

so they can see the animal. Oysters eat tiny floating plants and animals. Explain that 

oysters suck in water, filter the water to get their food as the water flows through their 

body, and then spit clean water back out. One oyster can clean half a gallon of water in 

15 minutes. The thousands of oysters that were in the Chesapeake Bay long ago kept 

the water clean, but now there are not enough. People try to clean the Bay water, but 

oysters are the pros. That is why people of all ages are helping oysters grow in the Bay 

again.

Extension

1. Send home the Student Response Sheet 2. Discuss with the class when returned to 

school. Make a chart with two columns. In the first column, list, with the class, the 

different types of filters used in class and those found at home. In the second 

column, list the results when they poured water or other items through filers at 

home. Help the students understand that successful filters remove unwanted items. 

Ask them why each one was a good filter. This helps them see a pattern in the 

activity.

2. Put together a box of small toys or other items and show it to the students. Then 

dump a couple tablespoons of Cheerios, sand, etc. into the box, and show it again. 

There should be an obvious size and shape difference between items in the box and 

the material to be filtered. Ask the students to design a filter to remove the 

Cheerios, but keep the other items in the box. They should draw their design and 

write about how it works if possible. Have them share the inventions with the class.

3. Read, Olly the Oyster Cleans the Bay, by Elaine Ann Allen, or another story describing 

how oysters filter water. Ask the students to draw a picture or write a story about 

how an oyster helps to the water/bay.

Evaluation

Formative: 

1. Class discussions and participation

Summative: 

1. Student Response Sheet 1 (Classroom filtering investigation)

2. Student Response Sheet 2 (Take home investigation)
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Education Standards

Three Dimensional Learning

Disciplinary Core 

Idea(s)

K-LS1.C Organization for Matter and 

energy Flow in Organisms

All animals need food in order to live 

and grow. They obtain their food from 

plants or from other animals. (K-LS1-1)

How Standard is Addressed

Students learn how the oyster 

filters water to gather its 

food.

K-ESS2.E

Plants and animals can change their 

environment.

Students learn how oysters 

change the polluted water of 

the Chesapeake Bay to clean 

water.

Science/Engineering 

Practice

Analyzing and Interpreting Data

Use observations (firsthand or from 

media) to describe patterns in the 

natural world in order to answer 

scientific questions. (K-LS1-1)

Engaging in Argument from Evidence

Construct an argument with evidence to 

support a claim. (K-ESS2-2)

Students list the results of 

each filter trial and are guided 

to see a pattern (good filters 

remove unwanted items).

Students use evidence from 

testing each filter to explain 

what makes a filter.

Cross – Cutting 

Concepts

Patterns

Patterns in the natural world can be 

observed, used to describe phenomena, 

and used as evidence.

Students view, discuss, and 

use multiple types of filters in 

use to understand that 

successful filters block and/or 

remove substances.

Common Core Standards

Ties to Common 

Core

ELA/Literacy

Writing (W)

2. Use a combination of drawing, 

dictating, and writing to compose 

informative/explanatory texts in which 

they name what they are writing about 

and supply some information about the 

topic.

Students view, discuss, and 

use multiple types of filters in 

use to understand that filters 

block and/or remove 

substances from water.

Maryland Environmental Literacy Standards

Ties to MD 

Environmental 

Literacy Standards

STANDARD 7: ENVIRONMENT AND 

SOCIETY

Topic A: Environmental Quality

Indicator: Investigate factors that 

influence environmental quality.

Students learn that the 

Chesapeake Bay is part of the 

environment and pollution is 

diminishing the quality of the 

water.
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Resources

Web 

Protecting Our Water Resources: Student Activities for the Classroom

Water and educational activities for Kindergarten through Ninth Grade

http://www.stormwater.ucf.edu/toolkit/vol3/Contents/pdfs/Student%20Activities/student_act

ivities.pdf 

Olly the Oyster

Visit this website for coloring pages, puzzles, word searches, crafts, and more. 

http://www.ollytheoyster.com

The Water Project

The Water Project is dedicated to providing clean, safe water to people in the developing world. 

Lesson plans provided for pollution and filtration experiments.

http://thewaterproject.org/resources/water_pollution_filtration_experiments.asp

Books

Allen, Elaine Ann. Olly the Oyster Cleans the Bay. Tidewater Publishers, May 1, 2008. ISBN-10: 

0870336037.

Bullard, Lisa and Xin. Watch over Our Water. Lerner Pub Group, September 1, 2011. ISBN-10: 

0761385177.

Tate, Suzanne. Pearlie Oyster: A Tale of an Amazing Oyster. Nags Head Art, Inc., June 1, 1989. 

ISBN 10: 0961634472.
Name  

Cleaning Our Water

Before

Dirty to Clean in 15: Student Response Sheet 1

1
AŌer

Dirty to Clean in 15: Student Response Sheet 1

2
Name

Is it a filter?

Look around your house for three items that could be filters. Draw and label a picture of 

each one in the boxes. Then test each one by pouring water through it. Mark yes or no.

Dirty to Clean in 15: Student Response Sheet 2

1

Which was the best filter? Why? Tell your answer to someone and have them write it.

Did it filter the water?

Yes No

Yes

Yes

No

No

1.

2.

3.