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3.1: Filtering Solutions for Clean Water

Created by: CK-12

Unit Overview

Contents

  • (Optional) Fine Filters: Pretest
  • (Optional) Fine Filters: Posttest

Name_______________

Date_______________

Period_______________

Fine Filters: Pretest

1. Which of the following types of contaminants can nanomembranes filter out of water? For which of these, would you typically use a nanomembrane for removal? Explain why or why not. (1 point each, total of 12 points)

Can a nanomembrane filter it out? Is a nanomembrane the best way to filter it out?
Bacteria Yes or No Yes or No
Why/why not:
Lead(Pb^{2+}) Yes or No Yes or No
Why/why not:
Salt (Na^+ and Cl^-) Yes or No Yes or No
Why/why not:
Sand Yes or No Yes or No
Why/why not:

2. Name two benefits that nanomembranes bring to the filtration of water that help to address the world’s problem of a scarcity of clean drinking water. (1 point each, 2 points total)

3. Describe three ways in which nanofilters can operate differently than traditional filters to purify water: (2 points each, 6 points total)

Name_______________

Date_______________

Period_______________

Fine Filters: Posttest

1. Which of the following types of contaminants can nanomembranes filter out of water? For which of these, would you typically use a nanomembrane for removal? Explain why or why not. (1 point each, total of 12 points)

Can a nanomembrane filter it out? Is a nanomembrane the best way to filter it out?
Bacteria Yes or No Yes or No
Why/why not:
Lead(Pb^{2+}) Yes or No Yes or No
Why/why not:
Salt (Na^+ and Cl^-) Yes or No Yes or No
Why/why not:
Sand Yes or No Yes or No
Why/why not:

2. Name two benefits that nanomembranes bring to the filtration of water that help to address the world’s problem of a scarcity of clean drinking water. (1 point each, 2 points total)

3. Describe three ways in which nanofilters can operate differently than traditional filters to purify water: (2 points each, 6 points total)

The Water Crisis

Contents

  • The Water Crisis: Student Data Worksheet
  • Fine Filters Initial Ideas: Student Worksheet
  • The Water Crisis: Student Quiz

Name_______________

Date_______________

Period_______________

Student Data Worksheet

Directions

Using the graphs and maps, answer the following questions. This activity will give you the opportunity to interpret some of the graphs and maps that you’ll see during the Water Crisis slide presentation during class.

Distribution of earth’s water.

Distribution of earth’s water.

1. According to the bar graphs in Figure 1, what percentage of the world’s water is fresh water?

2. What do these three divided bar graphs tell you about where the Earth’s fresh water resides?

Physical water scarcity refers to the lack of water to meet domestic, industrial, and agricultural needs. Areas of physical water scarcity are shown in red on the map in Figure 2 below. Economic water scarcity means that an area or country has insufficient financial resources to deliver safe, clean water to those areas that need it for drinking or agriculture. Areas of economic water scarcity are shown in orange in Figure 2.

Global map of water scarcity in 2006.

Global map of water scarcity in 2006.

Answer questions 3-8 based on information from the map in Figure 2.

2. Name the countries or global areas that are experiencing physical water scarcity.

3. What would you predict the climate to be in these areas and why?

4. Name the countries or global areas that are experiencing economic water scarcity.

5. Name the countries or global areas that are not experiencing any water scarcity.

6. What do you predict the difference in per capita income (average income per person) would be between regions with plenty of water and regions with economic water scarcity?

7. The southwestern United States is typically characterized as having a dry, arid climate. Why might this region be shown as having plenty of water even if it is dry and arid?

When water is taken from a natural source for human use, it is called “water withdrawal.” However, a country can never withdraw all of the fresh water that is theoretically available within its borders. Much of it is seasonal, or part of flood runoff, or rain that cannot possibly all be captured. Countries that withdraw a high percentage of their available fresh water are said to be under “freshwater stress” and are in danger of becoming considered “water scarce.” In the map in Figure 3, the light orange represents mild freshwater stress and the darker orange represents extreme fresh water stress. Blue areas are considered to be free from freshwater stress.

Global map of freshwater stress, 1995 and 2025 (predicted).

Global map of freshwater stress, 1995 and 2025 (predicted).

8. Compare the two maps above, showing freshwater stress from the year 1995 and projected to the year 2025. What are the changes that you see happening in which areas?

9. In Figure 4, what trend do you see in for the global population?

10. What would you predict the global population to be in 2060? Justify your prediction.

World population from 1950 to 2050 (predicted).

World population from 1950 to 2050 (predicted).

11. According to the graph in Figure 5, which sector uses the most water?

12. Which sector uses the least amount of water?

Global annual water withdrawal by sector, 1900-2000.

Global annual water withdrawal by sector, 1900-2000.

13. How does the trend in water consumption (Figure 5) compare to the trend in population (Figure 4) for the time period 1950-2000?

Average daily water use per person for selected countries, from 1998 to 2002.

14. According to Figure 6, which countries consume the most water?

15. Which countries consume the least water?

Average wealth for selected countries (purchasing power by person in 2005).

Answer questions 16-19 based on information from the graph in Figure 7.

16. How many countries have an average per person purchasing power of less than \$ 10,000?

17. How many countries have an average per person purchasing power of more than \$ 25,000?

18. How many countries have an average per person purchasing power of \$ 10,000- \$ 25,000?

19. What is the difference between the average per person purchasing power in the highest wealth country and the lowest wealth country?

Average daily water use per person and wealth.

Average daily water use per person and wealth.

20. According to Figure 8, does there seem to be a relationship between a country’s wealth and their average daily water consumption? If so, what is the relationship?

Name_______________

Date_______________

Period_______________

Fine Filters Initial Ideas: Student Worksheet

Write down your initial ideas about each question below and then evaluate how confident you feel that each idea is true. At the end of the unit, we’ll revisit this sheet and you’ll get a chance to see if and how your ideas have changed.

1. Why are water’s unique properties so important for life as we know it?

How sure are you that this is true?

Not Sure

How sure are you that this is true?

kind-of Sure

How sure are you that this is true?

Very Sure

End of Unit Evaluation
2. How do we make water safe to drink?

How sure are you that this is true?

Not Sure

How sure are you that this is true?

kind-of Sure

How sure are you that this is true?

Very Sure

End of Unit Evaluation
3. How can nanotechnology help provide unique solutions to the water shortage?

How sure are you that this is true?

Not Sure

How sure are you that this is true?

kind-of Sure

How sure are you that this is true?

Very Sure

End of Unit Evaluation
4. Can we solve our global water shortage problems? Why or why not?

How sure are you that this is true?

Not Sure

How sure are you that this is true?

kind-of Sure

How sure are you that this is true?

Very Sure

End of Unit Evaluation

Name_______________

Date_______________

Period_______________

Student Quiz

Write down your ideas about each question below.

1. What does it mean to have “clean fresh drinking water”?

2. Explain the term “water scarcity.”

3. Does water scarcity have an impact on human health? If so, what are some of the consequences?

4. Describe three reasons why some nations are experiencing a scarcity of clean drinking water.

5. Why is the water scarcity problem projected to increase?

6. Which sector––domestic, industrial, or agriculture––consumes the most water?

The Science of Water

Contents

  • The Science of Water Lab Activities: Student Directions
  • The Science of Water Lab Activities: Student Worksheets
  • The Science of Water: Student Quiz
  • Reflecting on the Guiding Questions: Student Worksheet

Lab Activities: Student Directions

Lab Station A: Surface Tension Lab

Purpose

The purpose of this lab is to investigate the property of the surface tension of water. This lab will look at the way that water sticks to itself to make a rounded shape, the way that water behaves as a “skin” at the surface, and a comparison of water’s surface tension with two other liquids, oil and soapy water.

Safety Precautions

  • Wearing goggles is dependent on your school’s safety criteria.
  • Caution needs to be exercised around hot plates and the alcohol burner.
  • Caution needs to be exercised around hot water and hot glassware.
  • Do not eat or drink anything in the lab.
  • Do not wear open-toed sandals in the lab.
  • Wear long hair tied back to prevent touching the substances at the lab stations.

Materials

  • 3 pennies
  • Available water
  • Small containers of water, oil, and soapy water
  • A dropper for each of the containers
  • A square, about 4'' \times 4'', of wax paper

Procedures

Counting Drops on a Penny

1. Check to make sure all of the materials needed are at your lab station.

2. Using a dropper bottle containing only water, count the number of drops of water that you can balance on top of a penny. When the water falls off of the penny, record the number of drops. Wipe the water off of the penny.

3. Repeat this procedure of counting and recording drops with oil and then with the soapy water.

Comparing the Shape of a Drop

4. Drop a small sample of each of the liquids––water, oil, and soapy water––on the wax paper. Draw the shape and label the shape of the drops made by each of the liquids on your worksheet. Wipe off the wax paper.

5. Answer the questions on your worksheet.

Lab Station B: Adhesion/Cohesion Lab

Purpose

The purpose of this lab is to investigate the property of cohesion and adhesion of water.

  • Cohesion is the molecular attraction exerted between molecules that are the same, such as water molecules.
  • Adhesion is the molecular attraction exerted between unlike substances in contact.

Cohesion causes water to form drops, surface tension causes them to be nearly spherical, and adhesion keeps the drops in place (http://en.wikipedia.org/wiki/Adhesion).

This lab will work with capillary tubing of various diameters to see the rate at which water is able to “climb” up the tubes. This is very similar to the way that water enters a plant and travels upward in the small tubes throughout the plant’s body. The “stickiness” of the water molecule allows the water to cling to the surface of the inside of the tubes.

You will see how the diameter of the tube correlates with the rate of traveling up the tube by measuring how high the dye-colored water column is at the end of the time intervals.

Safety Precautions

  • COOL GLASSWARE FOR A FEW MINUTES BEFORE PUTTING INTO THE COOLING BATH OR THE GLASSWARE WILL BREAK.
  • Wearing goggles is dependent on your school’s safety criterion.
  • Do not eat or drink anything in the lab.
  • Do not wear open-toed sandals in the lab.
  • Wear long hair tied back.

Materials

  • 4 pieces of capillary tubing of varying small sized diameters (no greater than 7\;\mathrm{mm} in diameter), 8-24\;\mathrm{inches} in length
  • Metric ruler
  • Pan of dyed (with food coloring) water into which to set the capillary tubing
  • Clamps on ring stands to stabilize the tubing so that it remains upright in a straight position

Procedures

  1. Check to make sure all of the materials needed are at your lab station.
  2. Set the capillary tubing into the dye-colored water from the largest diameter tubing to the smallest. Make certain they are all upright and secure.
  3. Record the height of each of the tubes in the table on your worksheet every 2\;\mathrm{minutes.}
  4. After 10\;\mathrm{minutes,} release the capillary tubing, wrap the tubing in paper towels, and deposit them in an area designated by your teacher.
  5. Answer the questions about this experiment on your lab sheet.

Lab Station C: Can You Take the Heat?

Purpose

The purpose of this lab is to investigate the heat capacity of water. You will measure the temperature of water (specific heat of water is 4.19 \;\mathrm{kJ/kg.K}) and vegetable oil (specific heat of vegetable oil is 1.67 \;\mathrm{kJ/kg.K}) over equal intervals of time, and will record your data and findings on your lab sheet.

Specific heat is the amount of energy required to raise 1.0\;\mathrm{gram} of a substance 1.0^\circ C.

Safety Precautions

  • Cool hot glassware slowly. Wait a few minutes before placing in cold water or the glass will break.
  • Wearing goggles is dependent on your school’s safety criterion.
  • Do not eat or drink anything in the lab.
  • Do not wear open-toed sandals in the lab.
  • Wear long hair tied back.
  • Use caution when working with fire or heat. Do not touch hot glassware.

Materials

Assemble two Erlenmeyer flasks or beakers, each containing one of the liquids,with a thermometer suspended into each liquid, from a clasp attached to a stand, inserted about midway into the liquid.

  • 2 equal amounts, about 100 \;\mathrm{mL}, of water and vegetable oil
  • 2 250-\;\mathrm{mL} Erlenmeyer flasks or 2 250-\;\mathrm{mL} beakers
  • 2 thermometers
  • 2 Bunsen burners or 1-2 hot plates
  • 2 ring stands: each ring stand will have a clamp to hold the thermometer. Use a screen if using a Bunsen burner rather than hot plate(s).
  • Cold water bath for cooling the Erlenmeyer flasks or beakers

Procedures

1. Set the cooled flasks containing their solutions on the ring stands or hot plate.

2. Take the initial temperature reading of each of the liquids.

3. Turn on the hot plate to a medium temperature, or, if using Bunsen burners instead, light them, adjusting the flame of each to the same level.

4. Record the temperature of the liquid in each flask every 2\;\mathrm{minutes} until 4\;\mathrm{minutes} after each liquid boils. Record the temperature in the table on your lab sheet.

5. After recording the final temperatures, move the Erlenmeyer flasks or beakers with tongs or a heat-resistant set of gloves into the cooling bath. Add small amounts of ice as needed to keep the water temperature cold.

DO NOT THRUST HOT GLASSWARE DIRECTLY INTO ICY WATER BEFORE COOLING BECAUSE THE GLASS WILL BREAK!

6. Answer the questions about this experiment on your lab sheet.

Lab Station D: Liquid at Room Temperature Data Activity

Purpose

The purpose of this activity is to discover how unusual it is, based on a substance’s molecular weight, that water is a liquid at room temperature.

Safety Precautions

None are needed, since this is a paper and pencil activity.

Materials

  • Water is Weird! Data Table
  • Lab worksheet for recording trends

Procedures

Data table 1 shows the physical properties of a variety of substances. This table is typical of one that a chemist would examine to look for trends in the data. For instance, is there any correlation with the color of the substance and its state of matter? Is there any correlation between the state-of-matter of a substance and its density? How does water compare to other substances?

  1. Examine the data table. Look for relationships between the physical properties of some of these substances. What do you notice that fits into any patterns? What is the opposite or is unusual to the most common pattern?
  2. Discuss the trends with your lab partner. Record your thoughts on your lab worksheet.
  3. Answer the questions about this experiment on your lab worksheet.

Water is Weird!

Data Analysis Activity

Water is Weird! How Do We Know?

We have been discussing the many ways that water is weird. Water seems pretty common to us. How do we know that it is unusual? Let’s compare water to some other substances and see what we can find, using the data table below.

Record the trends that you notice on your lab worksheet.

Physical Properties of Some Substances
Substance Formula Molar, mass, grams State of matter at normal room conditions Color Specific Heat \;\mathrm{J/g \ K} Density of gas, liquid, or solid Boiling Temperature, ^\circ C
Water H_2 O 18.0 liquid colorless 4.19 0.997\;\mathrm{g/cm}^3 100
Methane CH_4 16.0 gas colorless 0.423^{-162}\;\mathrm{g/cm}^3 -161.5
Ammonia NH_3 17.0 gas colorless 0.70 \;\mathrm{g/L} -33
Propane C_3H_8 44.1 gas colorless 0.493^{25}\;\mathrm{g/cm}^3 -42.1
Oxygen O_2 32.0 gas colorless 0.92 1.308 \;\mathrm{g/L} -182.9
Carbon dioxide CO_2 44.0 gas colorless 1.799 \;\mathrm{g/L} -78.5
Bromine Br_2 159.8 liquid red 0.47 4.04 58.8
Lithium Li 6.94 solid silvery, white metal 3.58 0.534\;\mathrm{g/cm}^3 1342
Magnesium Mg 24.3 solid silvery, white metal 1.02 1.74\;\mathrm{g/cm}^3 1090

Lab Station E: Now You See It, Now You Don’t A Dissolving Lab

Purpose

The purpose of this activity is to introduce the idea that different types of liquids may dissolve different substances.

Safety Precautions

  • Wearing goggles is dependent on your school’s safety criterion.
  • Do not eat or drink anything in the lab.
  • Do not wear open-toed shoes.
  • Tie long hair back.

Materials

  • 6 plastic cups
  • 6 plastic spoons
  • Water
  • Oil
  • Granulated salt
  • Granulated sugar
  • Iodine crystals

Procedures

  1. Fill 3 plastic cups 1/3 to 1/2 full with water.
  2. Fill 3 plastic cups 1/3 to 1/2 full with oil.
  3. Put about a half-teaspoon of salt into the water in one cup and another half-teaspoon of salt into the oil in one cup.
  4. Stir each for about 20\;\mathrm{seconds} or until dissolved.
  5. Record your observations in the table on your lab sheet.
  6. Repeat this procedure with sugar.
  7. Repeat this procedure using iodine crystals BUT only drop 2 or 3 crystals into the water and into the oil.
  8. Record your observations and answer the questions about this experiment on your lab sheet.

Lab Station F: Predict a New World! Inquiry Activity

Purpose

We all know that ice floats; we take it for granted. However, in nature, the solid form of a substance being less dense than the liquid form is extraordinary. What we don’t know or think about much is how our world would be affected if ice did not float in water. This “thought” activity is explores the worldly implications if ice had a greater density than water.

Safety Precautions

None are required because this is a paper and pencil activity.

Materials

  • A fish bowl with some fish and live plants

Procedures

1. Read the following. Look at the fish bowl. Think. Write your thoughts on your lab worksheet.

Assume that there will be one change in the way that nature behaves: On the day after tomorrow, worldwide, ice (the solid form of water) will now become denser than water, rather than its current state, which is less dense.

What will be the impact of this change?

Beautiful lake in early winter. [1]

Beautiful lake in early winter. [1]

2. Discuss this with your lab partner.

3. Answer the questions about this experiment on your lab worksheet.

Reference

Name_______________

Date_______________

Period_______________

Lab Activities: Student Worksheets

Directions: Go to the lab stations assigned by your teacher. Follow the directions for each lab that are posted at each of the lab stations. Conduct the lab activity and record your data on the lab write-up sheet. Answer the questions asked on the lab sheet. Be sure to pay special attention to the purpose of each lab before beginning the lab. You are encouraged to talk to your lab partners about the lab and to ask your teacher questions.

Lab Station A: Surface Tension Lab

Drops of Water

Fill in the table below with the number of drops you added to the penny of each substance before the liquid spilled over.

Water Oil Soapy Water
Number of Drops

Questions

1. What does a high surface tension do to the number of liquid molecules that can stay together?

2. Based on your evidence, compare the surface tension of these four substances.

3. After placing a few drops of each of the liquids on the wax paper, draw what the drops look like from the side view. Be sure to capture the relative height/flatness of the drop

Water

Oil

Soapy Water

Name_______________

Date_______________

Period_______________

Lab Station B: Adhesion/Cohesion Lab

Questions

1. Define adhesion

2. Define cohesion

3. Ask your teacher to provide you with the diameter of the capillary tubes if they are not labeled. In the table below, record the height of the liquid in capillary tubing of different diameters as you take your measurements.

Diameter of capillary tubing
2 \;\mathrm{minutes}
4 \;\mathrm{minutes}
6 \;\mathrm{minutes}
8 \;\mathrm{minutes}
10 \;\mathrm{minutes}

4. Based on your evidence, what statement can you make about water’s speed of climbing a capillary tube relative to the diameter (size of the opening) of the capillary?

5. What does this mean about how fast water is able to “climb” tubes within plants?

Name_______________

Date_______________

Period_______________

Lab Station C: Can You Take the Heat? Student Lab Sheet

Specific heat is the amount of energy that it takes to raise 1.0 \;\mathrm{gram} of a substance 1.0^\circ C.

Fill out the table as you conduct your experiment.

Liquids Water Temperature Vegetable Oil Temperature
2 \;\mathrm{minutes}
4 \;\mathrm{minutes}
6 \;\mathrm{minutes}
8 \;\mathrm{minutes}
10 \;\mathrm{minutes}
14 \;\mathrm{minutes}

Questions

1. Based on your evidence, which substance has the highest specific heat? The lowest?

2. Think about and explain the relationship between high specific heat of a liquid and hydrogen bonding.

3. Compare the boiling temperatures of water and of oil. What is the relationship between hydrogen bonding and boiling temperature?

4. What happened to the temperature of the water and the oil after boiling? Explain why.

Name_______________

Date_______________

Period_______________

Lab Station D: Liquid at Room Temperature Data Activity

Questions

1. What trends do you notice in the data table? Explain.

2. What is unusual about the most common pattern? Explain.

3. How does water compare to other substances?

Name_______________

Date_______________

Period_______________

Lab Station E: Now You See It, Now You Don’t A Dissolving Lab

A solvent is the liquid that is doing the dissolving. A solute is the substance that will be dissolved in the liquid.

Record your observations about how quickly and thoroughly each of the solutes dissolves in water and oil in the table below.

SOLVENT SOLUTES SOLUTES SOLUTES
Salt Sugar Iodine Crystals
Water
Oil

Questions

1. Summarize what you found in your experiment, based on your recorded observations.

2. Why do you think that some substances dissolve easier in one type of liquid than in another?

Name_______________

Date_______________

Period_______________

Lab Station F: Predict a New World! Inquiry Activity

Questions

1. Summarize your thoughts about the impact on the world if ice were denser than water.

Name_______________

Date_______________

Period_______________

Student Quiz

Write down your ideas about each question below.

1. Why does all bonding occur between atoms, ions, and molecules?

2. Draw a water molecule. Label the atoms that make up the water molecule with their chemical symbol. If there is an electrical charge or a partial electrical charge on any of the atoms, indicate that by writing the symbols on the atoms:

& + = \text{positive\ charge}  && -  = \text{negative\ charge} \\& \delta^+ = \text{partial\ positive\ charge}  && \delta^-  = \text{partial\ negative\ charge}

3. Explain the term “polar” molecule.

4. Why does water have an increased surface tension compared to most other liquids?

5. What is “hydrogen bonding”? What makes these bonds unique?

6. a. Define or describe “specific heat.”

b. How does water’s specific heat have an impact on our climate?

7. Is water’s specific heat, compared to other liquids:

High \Box or Average \Box or Low \Box ?

8. Are water’s melting and boiling temperatures, compared to other liquids:

High \Box or Average \Box or Low \Box ?

9. a. What happens to the temperature of the water in a pot on a heated stove as it continues to boil?

b. Explain what the energy is being used for that is heating the water at the boiling temperature.

10. Explain how a spider can walk on water.

11. Fill out the following table: Name and explain five of water’s unique properties, and provide an example of the phenomenon in nature caused by each of these properties.

Property of Water Explanation of Property Phenomenon Property Causes

Name_______________

Date_______________

Period_______________

Reflecting on the Guiding Questions: Student Worksheet

Think about the activity you just completed. What did you learn that will help you answer the guiding questions? Jot down notes in the spaces below.

1. Why are water’s unique properties so important for life as we know it?

What I learned in these activities:

What I still want to know:

2. How do we make water safe to drink?

What I learned in these activities:

What I still want to know:

3. How can nanotechnology help provide unique solutions to the water shortage?

What I learned in these activities:

What I still want to know:

4. Can we solve our global water shortage problems? Why or why not?

What I learned in these activities:

What I still want to know:

Nanofiltration

Contents

  • The Filtration Spectrum: Student Handout
  • Types of Filtration Systems and Their Traits: Student Handout
  • Which Method is Best? Student Worksheet
  • Comparing Nanofilters to Conventional Filters Lab Activity:
Student Instructions & Worksheet
  • Cleaning Jarny’s Water: Student Instructions & Report
  • New Nanomembranes: Student Reading
  • Reflecting on the Guiding Questions: Student Worksheet

The Filtration Spectrum: Student Handout

Osmonics Filtration Spectrum

Osmonics Filtration Spectrum

Types of Filtration Systems and Their Traits: Student Handout

Types of Filtration Max Particle Size (meters) Characterization Example Particles Disadvantages Diagram
Microfiltration(MF) 10^{-5} to 10^{-7}

Removal based on relatively large pore size, retains contaminants on surface.

Very low water pressure needed.

Often used as a pre-filter.

Sand, silt, clays, Giardia lamblia, Cryptospoidium, cysts, algae and some bacteria Removes little or no organic matter.Does not remove viruses.

Ultrafiltration (UF) 10^{-7} to 10^{-8}

Removal based on smaller pore size, retains contaminants on surface.

Low water pressure needed.

Suspended organic solids

Partial removal of bacteria

Most viruses removed

Most problems are with fouling. Cannot remove iron or manganese ions (multivalentions).

Nanofiltration (NF) 10^{-8} to 10^{-10} Removal based on very small pore size and shape and charge characteristics of membrane. Moderate pressure needed.

Suspended solids

Bacteria

Viruses

Some multivalent ions

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