ActivityGuides! - Discovery Education...Changing!the!Freezing!Temperature!of!Water! Extend!...

Activity Guides Water Module 2

Changing the Freezing Temperature of Water Concept: Mixing salt with water can change the temperature that ice will melt. (Session A: 40 minutes Session B: 40 minutes, inside, hands on) Materials (per group)

• salt • ice (cubed or crushed) • 2 plastic cups • optional: other substances such as sugar and sand • STEM journal • graduated cylinders • thermometers • water • marker • styrofoam cups • plastic spoons

Engage Ask students how ice melts. What causes ice to turn from solid to liquid? Most students will know that ice melts when it is heated. Explain that the melting temperature of water is 0°C, or 32°F. If ice gets warmer than 0°C, it will melt. If liquid water gets colder than 0°C, it will freeze. But how can we melt ice without heating it? How can we get ice to melt when it is below 0°C outside? Explore Session A Have students put equal amounts of ice in two cups. They should then pour salt into one of the cups. Observe what happens to the ice over time and record qualitative observations as well as quantitative observations. For instance, students may use a graduated cylinder to measure the amount of liquid water observed in each cup over time. The higher the amount of liquid water in each cup, the faster the rate of melting ice. Students should record their observations in their STEM journals using a chart such as the one below.

Changing the Freezing Temperature of Water

Elapsed Time Ice with no Salt Ice with salt

4 8 12 16

Discuss, How does salt affect how ice melts? What might happen if other substances are placed on the ice instead of salt? Have students connect their observations to the “salting” of roads during snow and ice storms in the winter. How does putting salt on the roads during a snowstorm help us? What eventually happens to the salt? How could salting the roads harm the environment? Session B Next, students can investigate whether the presence of salt affects the temperature of chilled water. Use a marker to label two cups as “water” and “salt solution.” Add 100mL of water to each cup. Place the thermometer in the cup labeled “water” and allow it to sit undisturbed for a few minutes. In the meantime, add 2 spoonfuls of salt to the cup labeled “salt solution” and stir to dissolve. Read the temperature of the water sample and record it. Use a table such as the one below.

Sample Initial Temperature Temperature After Ice Addition

Water Salt Solution

Place 4 ice cubes in each sample and stir with spoons. Be sure that students use separate spoons for stirring to avoid cross contamination. You may also want to remind students not to use the thermometers for stirring. Continue stirring for a few minutes to allow temperatures to equilibrate. Then measure the temperature of the water sample and record the results on the data table. Finally, measure the temperature of the salt solution and record the results. Sample Data table

Sample Initial Temperature Temperature After Ice Addition

Water 20 ⁰ C 1 ⁰ C Salt Solution 20 ⁰ C -‐2 ⁰ C

Ask, How does salt affect the temperature of water? How might this investigation help us understand why salt is placed on roads during winter storms? Discuss how salt dissolves into the liquid water in the ice and lowers its freezing point. Thus, if you sprinkle salt on the ice, you can melt it.

Changing the Freezing Temperature of Water

Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Discover how knowledge of melting ice with salt can be used to solve a problem.http://www.pbslearningmedia.org/resource/phy03.sci.phys.matter.zsalt/using-‐salt-‐to-‐melt-‐ice/

Additional Background Information

• Melting Ice with Salt: http://www.thenakedscientists.com/HTML/content/kitchenscience/exp/melting-‐ice-‐with-‐salt/

• Why Does Salt Melt Ice? http://antoine.frostburg.edu/chem/senese/101/solutions/faq/why-‐salt-‐melts-‐ice.shtml

• Why do they use salt to melt ice on the road in the winter? http://science.howstuffworks.com/nature/climate-‐weather/atmospheric/road-‐salt.htm

Density Wars: Fresh Water vs. Salt Water

Concept: Saltwater is denser than fresh water. As a result, fresh water can float on salt water. (30 minutes, inside, hands-‐on) Materials

• 3 transparent plastic cups • warm water • salt • food coloring • spoon • eyedropper

Engage Begin by asking students what the difference between ocean water and rain water is. Students will probably know that ocean water is salty and stream water is fresh. What are some differences between saltwater and freshwater? Explain to students that they will explore one important difference. Explore Have students fill two plastic cups with warm water. Make saltwater in one cup by slowly mixing salt into the water until it won’t dissolve any more. Add food coloring to the saltwater. Fill the eye dropper with saltwater and drip the saltwater into the clear freshwater one drop at a time. What happens? Redo the experiment, but this time color the freshwater. Put the freshwater in the dropper and drip it into the clear saltwater. What happens? Challenge students to explain why the saltwater fall to the bottom of a container of freshwater while freshwater floats at the top of a container of salt water Discuss the fact that saltwater is denser than freshwater. Explain that islands in the ocean are surrounded by saltwater, which is undrinkable. The saltwater sinks into the ground around the island. However, it does rain. This rain soaks into the ground and becomes ground water. The fresh water floats on top of the saltwater. People can drill water wells into this water for drinking water.

Density Wars: Fresh Water vs. Salt

http://www.epa.gov/climatechange/images/impacts-‐adaptation/FreshwaterLens.png Extend

• Measuring Density interactive: https://phet.colorado.edu/en/simulation/density Additional Background Information

• Freshwater Lens: http://www.epa.gov/climatechange/impacts-‐adaptation/islands.html

Density Wars: Hot Water vs. Cold Water

Concept: Hot water is less dense than cold water, so it rises. (20 minutes, inside, hands-‐on) Materials

• hot water • red food coloring • ice cold water • small jar with a narrow opening • large jar that the small jar can fit into

Engage Before beginning, ask students if they know what a hot spring is. Explain that it is a place where warm, even hot, water comes out of the ground. What happens when the water comes out of the ground? (It flows downhill just like a cold spring would.) Explain that there are also hot springs on the bottom of the ocean. They can be as hot as 400°C (the water can be this hot without boiling because it is under so much pressure). What happens to that water when it flows into the very cold ocean water? Have students use their bodies to demonstrate. Explore Follow the procedures described here to model the situation and find out: http://almostunschoolers.blogspot.com/2010/08/cold-‐and-‐hot-‐water-‐density-‐underwater.html Note that you can make this more realistic by working with salt water rather than fresh water. Follow up the experiment by challenging students to describe and explain what happened. Why did the hot water rise? What would happen if we made the water even hotter? What would happen if we put cold water in the small jar and set it in hot water? What happens to water that flows from a hot spring under the ocean?

Extend

• Hydrothermal Vents video: http://www.amnh.org/exhibitions/permanent-‐exhibitions/rose-‐center-‐for-‐earth-‐and-‐space/david-‐s.-‐and-‐ruth-‐l.-‐gottesman-‐hall-‐of-‐planet-‐earth/why-‐is-‐the-‐earth-‐habitable/life-‐that-‐lives-‐off-‐the-‐earth-‐s-‐energy/life-‐at-‐the-‐hydrothermal-‐vents/life-‐at-‐hydrothermal-‐vents-‐promos/life-‐at-‐hydrothermal-‐vents-‐video-‐gallery

• Find the Deep Sea Vent game: http://www.amnh.org/explore/curriculum-‐collections/deep-‐sea-‐vents/find-‐the-‐deep-‐sea-‐vent

• Searching the ocean for Deep-‐Sea Vents interactive: http://www.amnh.org/explore/curriculum-‐collections/deep-‐sea-‐vents/searching-‐the-‐ocean-‐for-‐deep-‐sea-‐vents



• Water Density: http://water.usgs.gov/edu/density.html • Water Temperature: http://water.usgs.gov/edu/temperature.html • Lost City Hydrothermal Vent Field: http://www.lostcity.washington.edu/

Density Wars: Ice vs. Water

Concept: Ice is less dense than liquid water, so it floats. (15 minutes, inside, hands-‐on) Materials

• clear container with watertight lid • water • ice cubes

Engage Have students discuss their experience with ice. Where have you seen ice? How is ice different from water? Use your body to show the difference between water and ice. Explore Ask students which is denser, water or ice? Which weighs more, one cubic centimeter of water or one cubic centimeter of ice? How can we find out? Have students place the ice cubes in the water. Does it sink or float? Challenge them to try to get the ice to sink by turning the container upside down. Why does the ice sink? How would Earth be different if ice sank in water? How would like be different for animals like polar bears, seals, and penguins? Extend

• Icebergs: http://oceanworld.tamu.edu/students/iceberg/ • Polar Bears and Sea Ice: http://www.polarbearsinternational.org/about-‐polar-‐bears/sea-‐ice

Additional Background Information • Water Density: http://water.usgs.gov/edu/density.html • Icebergs: http://oceanservice.noaa.gov/facts/iceberg.html • Glaciers and Ice Caps: http://water.usgs.gov/edu/earthglacier.html

Freezing Force Concept: Water expands when it turns into ice. When water in cracks in rocks freezes, it can break apart the rocks. (Session A: 15 minutes; Session B: 15 minutes, Session C: 15 minutes, inside, hands-‐on, multi-‐day) Materials

• a variety of hard disposable plastic containers with tight lids (this works best when the containers are not flexible, but yogurt containers and plastic water bottles will also work

• string • ruler • water • freezer • camera (optional) • graduated cylinder with a capacity of 100mL • STEM journal

Engage Ask students to describe ways that water changes when it gets cold. How is ice different from water? Have them think not just about temperature, but also shape/form, and density. Why does ice float? Explain that during the winter, many potholes form in roads. One reason for this is because ice can break apart the road. How does this happen? Explore Session A: Have students fill the container with water all the way to the top and put on the lid. There should be no air in the container. Have students make observations of the container including the shape of the container, the height of the container, the girth of the container (To find the girth use string to find the distance around the middle of the container and then measure the string with a ruler.), and the capacity or how much water the container can hold. Take photos if possible. Place the containers in a freezer until the next session. Session B: Remind students about the Expansion with Freezing activity they began in the previous session. What do you think happened when we put the containers of water in the freezer? Do you think anything happened to the containers as well as the water? Take the containers out of the freezer. What happened to the water? How have the containers changed? Does the ice take up more, less, or the same amount of space as the liquid water did? How do you know? Students should notice that the container has expanded or cracked because

Freezing Force

the water expanded as it froze. Allow students to re-‐measure the girth of the container to see if the measurement has changed and record both quantitative and qualitative observations in their STEM journals. Has the ice caused the plastic container to expand, causing an increase in the girth measurement? Has the overall shape of the container changed? Connect observations to the concept of why ice floats (it has the same mass, but takes up more space, so it is less dense). Extend the conversation by discussing: Why are plastic water bottles designed with lots of ridges? What happens when water seeps into rock and freezes? What can happen if this happens over and over? Show students a graduated cylinder with 50mL of water in it. Ask them to use what they have learned about freezing water to make a hypothesis of what will happen when the graduated cylinder is put in the freezer overnight. Students should write this hypothesis in their STEM journal. Session C: Show students the graduated cylinder they placed in the freezer during the previous session. Students should observe that the frozen water has now expanded past the 50mL marking on the cylinder. Provide time for students to compare the actual results of the investigation to the hypotheses they made in the previous session. Extend If there is time available, students can extend their exploration of the topic by searching for images of frost wedging. Challenge them to find actual photos of the results of frost wedging as well as diagrams showing how it occurs. Additional Background Resources

• Frost Heaving: http://www.pavement.com/Concrete_Pavement/Technical/Fundamentals/Frost.asp

• Why Does Water Expand When it Freezes? http://www.iapws.org/faq1/freeze.htm • What happens when your freeze water in a container so strong the water can’t expand

the ice? http://www.todayifoundout.com/index.php/2014/01/happen-‐froze-‐water-‐container-‐strong-‐water-‐couldnt-‐expand-‐ice/

From Gas to Liquid

Concept: Invisible water vapor exists in the air and can condense into a liquid when it cools or has something to stick to. (60 minutes, inside or outside, hands-‐on) Materials (per group)

• plastic cup • ice water • paper towels • magnifying glass • STEM journal

Engage Have students brainstorm places where water is found. Discuss the claim that there is invisible water in the air. Have you ever noticed that some days, the air feels wet, even though it isn’t raining? How can we prove that there is water in the air? Show students a cup with condensation on it. Discuss where the water on the cup comes from and how it gets on the cup. Guide students to use observations and reasoning to conclude that water exists as invisible gas in the air and condenses out of the air when the air cools. The water from the air now appears on the cup as condensation. Ask students, Does all air contain the same amounts of water? Explore Determine three different locations in which to compare the amount of water in the air (humidity) (e.g. outside, classroom, closet, refrigerator, locker room). Go to the first location. Have students fill a cup ¾ full with ice water. Use the paper towel to wipe the outside of the cup, making sure no water is on it. Set the cup down and observe it for 10 minutes. If the air is humid, students should be able to see water condensing from the air onto the sides of the cup. In their STEM journals, provide time for students to record their observations including what fraction or percent of the cup is covered with condensation. Repeat this same process with the other two locations. Have students compare the amounts of condensation observed in the different locations. Discuss which areas had the most moisture in the air as evidenced by the most condensation observed on the cup. Were students surprised by the results? Extend If there is time available, students can extend their exploration of the topic with the following resources:

From Gas to Liquid

• Learn more about relative humidity and how it affects how we feel. http://science.howstuffworks.com/dictionary/meteorological-‐terms/question651.htm

• Explore how condensation is involved in making artificial snow.

http://www.howstuffworks.com/outdoor-‐activities/snow-‐sports/snow-‐maker.htm Additional Background Information

• The Water Cycle http://science.howstuffworks.com/dictionary/geology-‐terms/water-‐info4.htm

Is Your Water Hard or Soft?

Concepts: “Hard water” is water with minerals dissolved in it. Soap does not lather up as easily in hard water as it does in soft water. (30 minutes, inside, hands-‐on NOTE: this can be extended as an outdoor investigation by having students collect and test water from natural sources like ponds, streams, and rain) Materials

• tap water • distilled water • two different brands of bottled

water (optional) • rainwater (optional)

• eye dropper • cup • jars with lids • liquid soap

Engage What happens when you put soap on your hands, mix it with water, and rub your hands? Explain that whether or not soap lathers well, and how easy it is to wash soap off your hands, depends on how “hard” or “soft” the water is. In this activity, students will be testing the hardness of the tap water. Explore Have students fill one jar about ¾ full with distilled water and the other jar with the same amount of tap water in the other jar. In a separate cup, mix some liquid soap with some distilled water. Put a drop of the soapy liquid into the jar with tap water, and shake it up. Does it foam? If not, add another drop. Add one drop at a time until the mixture foams when shaken. Count the number of drops of soapy liquid it takes to make the tap water foam. Repeat the procedure with the distilled water and the bottled water. Which type of water takes the most soap to foam up? Which takes the least? Would you rather have water that is very hard or very soft? Why do you think some water is hard and some is soft? Which do you think would be harder: rain water or water from an aquifer? Have students think about the fact that water dissolves minerals as it flows through rock. Additional Background Information

• Hardness of Water: http://water.usgs.gov/edu/characteristics.html#Hardness

Making Stalactites

Concept: Substances that are dissolved in water can come out of the water, or precipitate. (Session A: 30 minutes; Session B: 15 minutes; inside, hands-‐on, multi-‐day) Materials (per group)

• 2 jars • paper plates • hot water • sugar, baking soda, or Epsom salts • string or yarn • paperclips’ for weights • food coloring (optional) • camera (optional) • Making Stalactites Observation Sheet

Engage Ask students what they know about caves and cave formations. What do those formations have to do with water? Explore Session A: In this session, students will begin an experiment that they will revisit in the next sessions, and discuss in more detail in Week 4. Ask students what they think happens to a solution of sugar and water or salt and water when it is left to sit over time. What happens when a solution of water and some other substance flows slowly underground? Have students follow the procedures described here: http://chemistry.about.com/od/crystalrecipes/a/sodacrystals.htm. Note that this activity can be varied, using different solutes, different types of string or yarn, different colors of food coloring. Allow students to decide what materials they would like to work with so that there are a variety of results. Have students use the Observation Sheet to list the materials they used and make initial observations. Students should then place their experiments in a safe place for observation over the next few sessions. Session B (and subsequent sessions): Have students make observations each day. What is happening to the water? What is happening to the substance that was dissolved in the water? How is this similar to what happens in a cave? Connect this activity to the Dissolution activity. How do you think caves form in the first place?

Making Stalactites

Extend • How Caves Form interactive: http://www.pbs.org/wgbh/nova/earth/how-‐caves-‐

form.html • Vietnam Cave interactive: http://ngm.nationalgeographic.com/2011/01/largest-‐

cave/largest-‐cave-‐interactive Additional Background Information

• Stalactites and Stalagmites: http://science.howstuffworks.com/environmental/earth/geology/stalactite-‐stalagmite1.htm

• Geology of Caves: http://geomaps.wr.usgs.gov/parks/cave/

Measuring with Water Concept: The volume of an object can be found by submersing it in water and measuring how much water has been displaced. (75 minutes, inside, hands-‐on) Materials

• 100-‐mL graduated cylinders • variety of beakers 100 to 500 mL • variety of small solid objects to test – e.g. small rocks • marbles • toy figures • gram cubes (interlocking plastic cubes 1 cm on a side that have a density of about 1.0) • STEM journal

Engage Display a small box or other rectangular prism and ask students how they could find out how big the box was. In other words, what is the volume of the box? As the discussion progresses, bring out an irregular-‐shaped object like a large rock or a banana. How would they find out the size of the rock or the banana? Explore Once you’ve collected the objects to measure, display them so students can easily see and touch them. Pass some gram cubes out so students can handle them and tell students that the cubes have a volume of 1 cubic centimeter and that this is the same as 1 mL. The gram cubes can serve as a reference, so students have an idea of how big 1 mL is. Challenge students to guess the volume of each of the test objects and record their guesses in their journals. Make this guessing competitive so students will try to be more accurate than their classmates. Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Before showing students the video Introduction to Buoyancy, ask if any of them have heard of the story of how Archimedes was able to find the volume of the king’s crown.

• Once students have viewed and discussed the video, ask if they can imagine how an object like a submarine can change its buoyancy so that it can sink, float and hover in the middle.


• Just Dunk It: http://www.discoveryeducation.com/STEM/water/justdunkitexploration.cfm

Modeling Water Molecules

Concept: Water is made of tiny pieces called molecules, which are made of hydrogen and oxygen atoms. (30 minutes, inside, hands-‐on) Materials

• toothpicks • small edible objects that toothpicks will stick into such as marshmallows, gumdrops,

blueberries, strawberries, raspberries, grapes Engage Ask students if they know what water is made of. What does the tiniest “piece” of water look like? Ask why they think water is also known as H2O. Remind students that water is matter and all matter is made of atoms and molecules. A drop of water is made of millions of molecules of water. Explore Explain that each tiny molecule of water is made of 2 atoms of hydrogen (H) and 1 atom of oxygen (O). Show students some models as examples:

Have students use materials that you have assembled to make water molecule models. They may make as many as they wish. When students have finished, have them share and explain their models. Extend

• Build a Molecule Interactive: https://phet.colorado.edu/en/simulation/build-‐a-‐molecule

Additional Background Information • How Water Works:

http://science.howstuffworks.com/environmental/earth/geophysics/h2o.htm • Explore a 3-‐D Molecule of Water:

http://www.classzone.com/books/earth_science/terc/content/visualizations/es2201/es2201page01.cfm?chapter_no=visualization

Static Power

Concept: An object with a static charge can exert a force on a stream of water. (30 minutes, inside, hands-‐on) Materials (per group):

• 3 Styrofoam cups • inflated balloons • plastic comb or rod • toothpick • wool cloth (optional) • water

Engage Challenge students to make the inflated balloons stick to a wall without tape or glue. Most will know that rubbing a balloon on hair will give it the ability to stick to a wall. Why is the balloon sticking to the wall? What force is holding the balloon to the wall? What do you think would happen if we brought this balloon close to a stream of water? Explore Follow the procedures here: http://www.scientificamerican.com/article/static-‐electricity-‐bring-‐science-‐home/. This article also provides important background information and explanations. Note that you may use a plastic comb or rod or a balloon in place of one of the cups. You may also use a wool cloth instead of hair to charge the objects. The activity can also be done in a sink. Before using the charged object to change the stream of water, have students observe what happens when the water is falling from one cup into another. What path is it taking? What force is making the water fall from the faucet into the sink? Why is it falling in a perfectly vertical line? After they use the charged object to attract the water, challenge students to describe and explain what is happening. How did the path of the water change? What force caused the water to move? Encourage students to experiment by changing variables such as water temperature, the size of the stream of water; size of the charged object, and distance between the charged object and the stream of water. Extend

• Static Electricity Simulation: https://phet.colorado.edu/en/simulation/balloons

Additional Background Information:

Water Content of Foods

• Static Electricity: http://www.sciencemadesimple.com/static.html

Surface Tension of Water Concept: Surface tension is the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of the water molecules. (65 minutes, inside, hands-‐on) Materials

• coin (penny, dime, or nickel) • 25 mL graduated cylinders, 2 • 200 mL beaker • eyedroppers, 4 • STEM journal

Engage Demonstrate some examples of water beading by using an eyedropper to set some drops of water on a smooth surface. Gently place a needle or paper clip on the surface of a bowl of water. Dip a finger in a glass of water and slowly withdraw it to expose a drop of water briefly clinging to your finger before it falls off. Explore

1. Determine the volume of one drop of water by filling a graduated cylinder with 10 mL of water and counting the number of drops required to reach a volume of 11 mL.

2. Calculate the volume of one water drop by dividing 1 mL by the number of drops required to reach 11 mL. For example, if 5 drops are required to reach 11 mL, divide 1 by 5, which is 0.2 mL. Thus, there would be 0.2 mL in one drop of water.

3. Record this calculated volume in your STEM journal. 4. Predict in your notes how many drops of water can fit on the surface of a coin without

spilling over the sides of the coin. Write your prediction as “number of drops” and as milliliters.

5. Test your prediction by carefully placing drops of water, one at a time, onto the surface of the coin. Be sure not to touch the surface of the coin (or the water drops already on the coin surface) with the eyedropper. Also be sure to keep count of the water drops. Stop when the final drop of water placed on the coin runs over the sides of the coin. Do not count this drop in your results.

6. Record the results in a data table as “number of drops” and as milliliters. Extend If there is time available, students can extend their exploration of the topic with the following resource:

• Surface Tension and Water: http://water.usgs.gov/edu/surface-‐tension.html

Surface Tension of Water

Additional Background Information • Surface Tension of Water Tutorial

http://edtech.boisestate.edu/snelsonc/examples/surface_tension_tutorial.htm • How Surface Tension Works: http://science.howstuffworks.com/surface-‐tension-‐

info.htm

Boat Building Design Challenge

Concept: Goods can be transported through water. Boats can be made from materials that are denser than water because of the buoyant forces of water. (75 minutes, inside, hands on) Materials

• one half stick (about 2 ounces or 50-‐60 grams) of modeling clay (non-‐hardening) per student

• one tub of water, at least six inches deep, per four or five students • 100+ large washers, e.g., 1.5" fender washers (available from hardware stores) • paper towels (dozens) • one roll of waxed paper tape (masking or transparent) • STEM journal

Engage Display a transparent container filled with water. Place both a buoyant object (and apple) and an object that is not buoyant (like a marble) in the water to show that some objects float and some sink. Ask students why the one object floats and the other sinks. Explore Provide the materials above for each student and follow the procedures found on this Web site: http://www.teachengineering.org/view_activity.php?url=collection/duk_/activities/duk_float_mary_act/duk_float_mary_act.xml. Challenge and assist students to design and make a boat out of clay that will float and hold a load of washers. Modify the procedures as needed. Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Buoyancy interactive: https://phet.colorado.edu/en/simulation/buoyancy Additional Background Information

• Buoyancy: http://www.teachengineering.org/view_lesson.php?url=collection/duk_/lessons/duk_float_mary_less/duk_float_mary_less.xml

• Why boats float: http://science.howstuffworks.com/science-‐vs-‐myth/everyday-‐myths/question254.htm

Create Your Own Slip and Slide (60 minutes) Materials

• grassy area • roll of plastic, 5ML or thicker • garden Staples • duct Tape • hose • timer

Procedures Follow the instructions for creating a slip and slide at Make Your Own Slip and Slide. Have students take turns, one at a time, running up to the slip and slide and sliding down it. Students can compete to see who can travel the farthest. Students can also use times to see who can go the fastest. *Make sure students use the slip and slide one at a time. The last student to use it should be off when the next one starts. Connect to Science

• What properties of the plastic make it good for a slip and slide? • What forces are at work run when you begin sliding? • What forces are at work during your slide? • Why is it easier to slide on plastic than grass? • Why is it easier to slide on wet plastic than dry plastic? • What would happen if there was absolutely no friction between you and the slide?

From Liquid to Gas

Concept: Water can evaporate, or turn from liquid to gas in the air. The rate that water evaporates depends on the temperature of the water and how much area is exposed to the air. (45 minutes, outside or inside, hands on) Materials

• 3 regular brown paper towels (test ahead of time to determine if they can hold 5 drops of water concentrated in a circular spot without tearing. Adjust the number of drops as needed. See procedure described in the Explore part of the task.)

• Water (hot and room temperature) • Droppers (1 per student) • Sealable baggies • Light source such as a window • Construction paper • Tape • STEM journal

Engage Show students a piece of paper with a wet spot on it. Ask students to imagine that they have a homework assignment to turn in, but accidentally, the paper has gotten wet from the rain. Explain that eventually, the water spot will dry as a result of evaporation, but you want to speed up the process. Ask students to brainstorm some ways that they might speed up the evaporation process. Explore

1. Divide students into groups of three. 2. Discuss various strategies that might speed up the evaporation process. Show students

the supplies that are available to them (hot water, sealable baggies, light source such as a window, construction paper) Allow each group to choose two strategies they think will be the most effective for causing the water to evaporate quickly using only the resources you have provided. (Some ideas you might observe: fanning the paper, taping the paper to a window so the sunlight can heat it, placing hot water in a sealable baggie and placing the paper on top to add heat, placing the paper between two heavy books, etc.)

3. After student groups have chosen two strategies they want to test, provide each student with a brown paper towel). Simultaneously the three students in the group should use the droppers to place 5 drops of water on each brown paper towel. This will create a fair test as all students will be starting the investigation at the same time. Encourage students to concentrate the drops in the same area so that a circular water spot appears on the paper.

From Liquid to Gas

4. After students have a circular water spot on the paper they should measure the area of the spot and describe it. This can be found using the formula pi times the radius squared. For one of the circular water spots, students should leave it alone. This is the control for the investigation. For the other two water spots, students should begin implementing their chosen strategies in an attempt to cause the water to evaporate quickly.

5. Every 3 minutes, students should record the area of the water spot along with any other qualitative observations as in the chart below.

Minutes Evaporation Observations (control)

Evaporation Strategy 1

Observations

Evaporation Strategy 2

Observations 0 3 6 9 12 15

6. By comparing how the area and the description of the water spot change over time as a result of the evaporation strategy, students should be able to determine at the end of the investigation which strategy appeared to cause the fastest evaporation rate.

Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Discover why water evaporates at room temperature.

http://science.howstuffworks.com/innovation/science-‐questions/10-‐science-‐questions-‐you-‐should-‐know10.htm

• Explore how temperature affects evaporation by completing the middle school investigation found at

• http://www.ehow.com/info_12181584_kids-‐science-‐experiments-‐evaporation.html Additional Background Information

• The Water Cycle http://science.howstuffworks.com/dictionary/geology-‐terms/water-‐info4.htm

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US Navy Sea Trials

Concept: The design of a ship affects its speed, maneuverability, and stability. (25 minutes, inside, Internet) Materials

• Internet • STEM journals

Engage Ask students what they know about ships. What are large container ships used for? Where do they travel? What is the shape of a ship? What problems do ships encounter out at sea? How do you think the way that a ship is designed affects its ability to do its job? Explain that in this interactive, students will explore some variables in ship design and how those variables influence how well a ship works. Explore Have students explore the interactive call “Sea Trials” in which they design a ship and test it for seaworthiness. When students go to the Web site below, they will need to click on the interactive icon, enter their first name, and choose “Sea Trials.” http://www.navystemfortheclassroom.com Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Buoyancy Basics: http://www.pbs.org/wgbh/nova/lasalle/buoybasics.html • Buoyancy Brainteasers: http://www.pbs.org/wgbh/nova/lasalle/buoyancy.html


• Buoyancy: http://www.teachengineering.org/view_lesson.php?url=collection/duk_/lessons/duk_float_mary_less/duk_float_mary_less.xml

• Why boats float: http://science.howstuffworks.com/science-‐vs-‐myth/everyday-‐myths/question254.htm

Water Properties What Do You Know? Concept: Water has some very unusual properties. (40 minutes, inside, Internet) Materials

• Internet • STEM journal

Engage Ask students if they can name properties of water. List the properties on the board or chart paper. What are some of the more unusual properties? Explore Allow students to access the USGS Web site Water Properties True/False Quiz: http://water.usgs.gov/edu/sc3.html and let them take the Water Properties True/False Quiz on their own. When they finish the 10-‐question quiz, students should “Get the Answers” and study the explanations that are provided. This could be done individually or as a group and should allow for some discussion. Ask if students have had personal experience with any of the properties asked about in the quiz. For example, has anyone tried to boil water at a high altitude; has anyone dealt with condensation on a cold surface; etc. Extend If there is time available, students can extend their exploration of the topic with the following resources:

• Water properties and measurements: http://water.usgs.gov/edu/waterproperties.html Additional Background Information

• Teacher resources for water science: http://water.usgs.gov/edu/teachers-‐water.html •

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