Science

Hydrosphere

4-6

Students will be able to:
Build a model filtration system to discover one way that water can be purified.
Observe and record changes in the contaminated water.
Compare and contrast pH, hardness, color, and clarity of water before and after filtration.
Draw conclusions about the efficiency of the water filter model.

The water we use today is the same water that was here when the Earth was formed. How is water provided for astronauts aboard the space shuttle? Water does not need to be recycled on the space shuttle because fuel cells produce plenty of water as a byproduct. However, there are no fuel cells on a space station, so water must be used carefully, then cleaned and used again. What kinds of water will be recycled? Water used for showers, shaving, food preparation, and even urine. The International Space Station will use chemical processes to remove contaminants and the Urine Processor will remove solids in urine using distillation. Distillation is an evaporation process that separates water from the solids and condenses the water. Solids and some volatile components will remain as a liquid brine that will be returned to Earth for disposal. Final processing consists of removal of all remaining volatiles by heating and treatment with chemicals to prevent microbial growth.
To ensure that the crew remains healthy, all water must meet clean water standards. Water will be checked often to ensure it meets water quality standards. The water will also be monitored closely for bacteria, pollutants and proper pH. The space station water must fall in the 6.0-8.5 range. Water on the space station is almost sterile and is much cleaner than tap water at home or in school.
Students will build a simple water filter to simulate one type of water purification system. Six different types of contaminants will be filtered to determine the effectiveness of filtration as a way to purify water.

Essential Question
Is mechanical filtration an effective way to purify water?

Preparation & Management
This activity works best as a joint Lab activity. Prior to doing this activity, you should contact several other labs and arrange to do this activity as a cooperative experiment.

One lab will complete tests 1-3 and the other lab will complete tests 4-6. Then, students from both labs share their results and determine if the filtration system will work for each of the different contaminants.

3. Students need a basic understanding of the water cycle, recycling, pH, and hardness of water.

Use the following steps to prepare the wastewater:
Fill each jar with 500 mL water.
Add soil to water, stir and label this jar #1. Students will filter the water to determine if the filter will clean the mud from the water. They will need to observe water clarity before and after filtering. (The filter will clean the water.)
Add salt to water, stir and label this jar #2. Students will filter the water and observe water clarity before and after filtering. After filtering, students should pour a small amount of filtered water into an evaporating dish or a small cup and a small amount of unfiltered water into an evaporating dish or a small cup. Place them under a lamp to evaporate and determine the effectiveness of the filter in removing salt. (The filter will not remove all the salt.)
Add food coloring to water and label this jar #3. Students will filter and observe color of water before and after filtering. (The filter will remove the food coloring.)
Add hand soap to water and label this jar #4. Students will beat the water with an egg beater to observe bubbles, then filter the water. After filtering, students will test the water again with the egg beater to determine the effectiveness of the filter in removing soap from wastewater. (The filter will remove the soap.)
Add pepper to water and label this jar #5. Students will filter and observe particles in the water before and after the filtering. (The filter will remove the pepper.)
Add vinegar to water and label this jar #6. Students will test the pH of the water before filtering and after filtering to determine the effectiveness of the filter in changing the pH. The acceptable pH range of water on Vista is 6.0-8.5. (The filter will not change the pH of the water.)


Procedures
1. At the activity station, students will discuss how water on Earth is recycled.

2. Students will test one way water can be purified by constructing a water filtration model and using it to recycle one type of wastewater. Do not allow students to drink the water after filtering. The filtering system will not purify water for drinking.

3. Have the students place the coffee filter over the mouth of the two-liter bottle and secure it with a rubber band.

4. On top of the filter, place 5-6 cm of aquarium charcoal.

5. Add 8 cm of sand and then 5-6 cm of aquarium gravel.

6. Place the bottle on top of the cup to catch the filtered water.

7. Student teams will be assigned a task and a jar of waste water to filter. Students will follow directions and record observations on the student worksheet.

Transfer & Extensions
Have students watch and complete the video hook Water in Space.

Students will work collaboratively. Students will work in groups of 2.

2 class periods. 1 Hr per class.

Activity modified from: http:/spacelink.nasa.gov/Instructional.Materials
/NASA.Educational.Products/International.Space.Station.Clean.Water/
Water.Purification.for.the.ISS.pdf

Per team:
• 1 two-liter bottle with the bottom cut off
• 1 coffee filter or small piece of cheesecloth
• 1 rubber band
• Aquarium gravel
• Sand
• Aquarium activated charcoal
• 2 plastic cups of water (500 ml)
• 1 jar (for wastewater)

Per class:
• 1 spoonful of soil
• 1 large clear plastic cup
• 1 spoonful of pepper
• 2 drops of liquid hand soap
• 1 egg beater
• 2 spoonfuls of vinegar
• 2 drops of red food coloring
• 2 spoonfuls of salt
• 1 plastic spoon
• 1 evaporation dish or small cup