chemistry_book by Wonders of Our World

Chemistry Experiments

Index Acid-Base Chemistry

Chemical and Physical Changes

Chromatography - Food Coloring

Chromatography - Grape Soda

Chromatography - T-shirts

Ice Cream Science

Light Sticks

pH Values of Common Household Materials

Supply List

References

Childrenâ&#x20AC;&#x2122;s Literature

Notes

Acid-Base Chemistry

Index

Chemical compounds are grouped together based on similar properties. Acids are chemical compounds that are sour or bitter. These compounds when placed in water dissociate to form hydrogen ions. Bases are a group of compounds that have opposite properties to acids. Bases are characteristically slippery. A number scale called a pH scale, which spans from 0 to 14, is used to provide information on how strong an acid or base is. Values on the pH scale between and 7 are acidic; values above 7 are basic. A pH value of 7 corresponds to the neutral condition, neither acidic nor basic. Pure water is neutral. Food is often acidic in nature and household cleansers are often basic. A universal indicator will be used in this experiment to determine whether solutions of interest are acidic, basic or neutral. An indicator is a compound that when dissolved in water changes color depending on the acidic, basic or neutral condition of the solution.

Materials

A universal indicator (pH = 1-13) Alternatively red cabbage solutions can be used as indicators. Test solutions (lemon juice, vinegar, tomato juice, milk, water from different sources, antacid, milk of magnesia, household ammonia, toothpaste, aspirin, vitamin C, scouring powder, detergent, shampoo and conditioner) Buffer solutions at pH = 2,4,6,8,10 Small glass vials (10 mL) with caps

What To Do

Fill a glass vial almost all the way with a test solution. Add two drops of universal indicator and cap the vial. Shake the closed vial and observe the resulting color. Compare the color of the test solution to the colors of the buffer solutions. The pH of the test solution can be estimated by matching the color of the test solution to the color of the buffer solutions with known pH values. Find the pH value of a variety of test solutions by repeating the steps above. After the pH values of the test solutions have been determined sort the solutions into acid, base, and neutral groups.

Questions

1. Report the pH values of the solutions of interest or alternatively report whether the solutions are acidic or basic based on the observed color of the test solutions. 2. What trends do you notice among the food samples and among the cleansers? 3. Compare the pH values of hair shampoos and conditioners. What are the observed similarities or differences?

Summary

The universal indicator will have a bright red color for highly acidic conditions and will change to orange as the solution conditions approach neutral pH. More and more basic solutions will become blue in color. Test solutions can be grouped into acid, base, or neutral groups. The work can be checked by referring to the list of pH values for common household products.

Source

“Chemical Demonstrations: A Handbook for Teachers of Chemistry.” Vol. 3., Bassam Shakhashiri, University of Wisconsin Press, 1989. “Science Is.” Susan V. Bosak, Scholastic Press, 1991. © S. Olesik, WOW Project, Ohio State University, 2002.

Chemical and Physical Changes

Index

This experiment provides hands-on experience with chemical and physical changes. Safety goggles must be worn!

Materials

Water Vinegar Hydrogen Peroxide (3% solution) Epsom salt Baking soda Alka-Seltzer® tablets Potato Powdered laundry detergent Empty film containers Ice Boiling water Beakers or clear plastic cups

What To Do

Chemical Changes Put on safety goggles! Pour baking soda into a clear plastic cup so that the bottom of the cup is just covered. Slowly add vinegar to the cup to fill it about halfway and observe the formation of carbon dioxide gas, an indication that a chemical change has taken place. Place a piece (about the size of large eraser) of raw potato in a clear plastic cup. Add enough hydrogen peroxide to cover the piece of potato and observe the formation of oxygen gas as the enzymes from the food break the peroxide into water and oxygen gas. The gas formation is an indication that a chemical reaction is taking place. The kids can also feel the outside of the container – it will be cold to touch. This is another indication of a chemical reaction. Place an Alka-Seltzer® tablet in a cup of water and observe the release of carbon dioxide gas. Then, combine half of a tablet with some water in a film container, cap it tightly, step back at least 5 feet, and wait for the lid to pop off. The carbon dioxide being formed builds up pressure inside the sealed film container until the lid can no longer hold it. It will make a loud noise and the lid will pop off, shooting into the air. Avoid setting the canister directly below light fixtures, because the lid may be able to break light bulbs. Please be careful! Combine half of a cup of warm water with about a teaspoon of powdered laundry detergent and stir to dissolve. Make small amount of Epsom salt solution by dissolving 1 part magnesium sulfate in two parts water. Add a drop of food coloring to the Epsom salt solution, and then use an eyedropper to add a few drops of the colored solution to the laundry detergent solution. As a clear indication of a chemical reaction, a solid will immediately form and settle to the bottom of the cup. These solutions may already be prepared and labeled for use. If so, fill the cup about one fourth of the way with the detergent solution and pour in a few milliliters of the Epsom salt solution to observe the formation of the solid. Physical Changes Dissolve Epsom salt in water until no more will dissolve to make a saturated solution. Paint a few drops of this solution on a piece of dark paper to watch the salt crystals reappear as the water evaporates. The change in form, from solid to part of a liquid solution, back to solid, is purely physical. Observe ice melting and water boiling to learn about phase changes as physical changes.

Questions

1. Why is it important to wear safety goggles? 2. What is a chemical change? What is a physical change? 3. How can the two types of changes be distinguished? What are the signs of a chemical change? 4. What are the signs of a physical change? 5. What are some examples of chemical changes? 6.What are some examples of physical changes?

Summary

Chemical changes are chemical reactions; they transform substances into different substances. Chemical changes are indicated by a number of signs, including, but not limited to, the formation of gas, the formation of solid, a change in temperature, and evolution of light. Physical changes do not form new substances and do not change the chemical nature of the substances involved. Physical changes are those that change only the physical properties of a substance without changing the chemical properties.

Source

“The Best of Wonder Science.” Ed. Jay Whitney, Delmar Publishers, 1997. “Solids, Liquids and Gases.” The Ontario Science Centre, Kids Can Press, 1998. © S. Olesik, WOW Project, Ohio State University, 2002.

Chromatography - Food Coloring

Index

This experiment illustrates a chromatographic separation as a good example of a physical change.

Materials

1 bottle of 5% isopropyl alcohol 1 bottle of 20% isopropyl alcohol 1 bottle of 70% isopropyl alcohol 1 bottle water 1 10 mL plastic syringe 1 C-18 “Sep- Pak” chromatographic bed (obtained from Waters Associates, Milford, MA) (1mL volume tube is OK) 1 piece of white paper 1 clear plastic cup with 10 drops of red food coloring + 10 mL water 1 clear plastic cup with 10 drops of blue food coloring + 10 mL water

What To Do

Place the two cups of food dye on a white sheet of paper to see the two different colored solutions. Next predict what will happen when the two solutions are combined. Combine the two solutions. A purple solution will result. Draw 10 mL of water into the syringe. Slowly force the water through the column. This will wet the column before the separation process. Next pull 1 mL of the purple solution into the syringe. Connect the Sep-Pak column to the syringe. Inject the purple solution onto the column. Collect the solution that emits from the column. The solution should be nearly colorless. Flush 10 ml of 5 % isopropyl alcohol slowly onto the column. Collect the emitted solution in a plastic cup. (This solution should be red.) Next flush the column with 10 ml of 20% isopropyl alcohol. Collect the emitted solution in the plastic cup (This solution should be blue). The column will still be holding a red layer. This is because the red dye was actually produced by combining two different red food dyes. Next flush the column with 70% isopropyl alcohol. The emitted solution will have a slight red tint to it. Take 1 mL of the original mixed food color solution and dilute it with 35 mL of water. Ask class what they expect to see when the red and blue solutions are combined (hopefully, many will say they should get the same color as the solution just prepared). The final two solutions should look identical in color. This demonstrates that chromatographic separation is a physical change.

Source

WOW Staff, 2002 © S. Olesik, WOW Project, Ohio State University, 2002.

Chromatography - Grape Soda

Index

In an effort to identify the chemical components that causes plants to be green, Michael Tswett discovered the technique of chromatography in 1903. Chromatography (“color writing”) is a means of separating the components of mixtures (i.e. chromatography is a method that only involves physical changes). In this experiment the food dyes used to create the color of “grape” soda will be separated into the basic components.

Materials

1 Grape Soda Pop 1 C-18 “Sep- Pak” chromatographic bed (obtained from Waters Associates, Milford, MA) (1mL volume tube is OK) 1 Graduated cylinder 4 100 mL beakers 4 small test tubes 1 bottle of 5% isopropyl alcohol 1 bottle of 20% isopropyl alcohol 1 bottle of isopropyl alcohol Distilled water 25 or 50 mL plastic syringe

What To Do

Draw 10 mL of isopropyl alcohol into the plastic syringe. Connect the syringe to the column. Slowly force the 10 mL through the column. This will wet the separation bed. Disconnect the syringe and fill the syringe with 10 mL of grape soda. Inject the soda onto the top of the column. Draw 10 mL of the 5% isopropyl alcohol solution into the syringe. Connect the syringe to the column; flush this solution through the column. Collect the solution in a 100 mL beaker as it flows out of the column. Label the beaker (Beaker 1). Disconnect the syringe from the column. Draw 10 mL of the 20% isopropyl alcohol solution into the syringe. Reconnect the syringe to the column and force it through the column. Collect the solution in a 100 mL beaker as it flows out of the column. Label the beaker (Beaker 2).

Questions

1. What color is the solution in Beaker 1? 2. What color is the solution in Beaker 2? 3. Combine the two solutions and compare the color of this solution to that of the grape soda. Note: Dilute the grape soda (10 mL grape soda combined with 10 mL distilled water) before making the comparison.

Summary

The food dyes are more soluble in isopropyl alcohol than in water. With the addition of 5% isopropyl alcohol to water, the orange dye will flush through the column. Next, when the higher proportion of isopropyl alcohol is added to the column the blue dye will flush off the column. From the separation at least two dyes are used to color the grape soda. The colors should match. All solutions may be poured down the drain when finished.

Source

“Chemistry Demonstrations: A Handbook for Teachers of Chemistry.” Vol. 1, Bassam Z. Shakhashiri, 1989, University of Wisconsin Press. M. Bailey, The Ohio State University. © S. Olesik, WOW Project, Ohio State University, 2002.

Chromatography - T Shirts

Index

This experiment allows the application of the chromatographic method to the separation of marker dyes. These chromatograms are produced on t-shirt material.

Materials

100% cotton T-shirt Prang markers Water Plastic wrap Plastic tub

What To Do

If the t-shirt is new, make certain that the shirt has been washed before attempting the chromatographic experiment. This is necessary to remove the sizing that may be present in the shirt. Place plastic wrap between the front and back of the t-shirt. Cover the bottom of the plastic tub with water. Place a dot of marker on the bottom of the shirt. Make certain that the dot is high enough on the shirt so that it doesn’t dip into the water layer on the bottom of the tub. Water will climb up the t-shirt based on capillary action. The dot will also begin to move up the shirt and as it does, the dyes that make up the color will move at different rates and then will appear as separate bands connected to each other. Once the chromatograms are developed on the t-shirt, treat with fabric medium to keep the colors from washing out of the t-shirt when washed. Make certain the t-shirt is washed with cool water when washed. Fabric treatment medium may be Jo Sonja Textile Medium. (Chroma Acrylics, Inc, Hainesport, NJ)

Summary

The net result of this experiment is the physical separation of the dyes. The colors of the dyes are separated down the length of the t-shirt. This is one of the few experiments in which the results may be worn after the experiments are finished. Brown is one of the best dyes. A separation of blue, red, orange and yellow is observed. Orange is separated into yellow and red bands. Blue is separated into green, yellow and red bands.

Source

“T-shirt Chromatography.” J. M. Buccigross, J. Chem. Education, 978-979 (1992). WOW staff, 2002. © S. Olesik, WOW Project, Ohio State University, 2002.

Ice Cream Science

Index

Ice cream is partially frozen foam with an air content of 40 - 50% by volume. The foam consists of liquid and solid water (ice crystals) and fat globules; it exists as an emulsion, a stabilized mixture of immiscible droplets or particles. These experiments will look at the properties of ice cream when it is made by chilling it to the very low temperature of liquid nitrogen (-196 oC). In addition, the change of nitrogen from gas phase to liquid phase will be observed.

Materials

2 Stainless Steel large mixing bowls 2 Wooden Spoons 2 Measuring cups or Beakers 2 Cups Heavy Whipping Cream 2 Cups Half and Half 4 Cups Skim Milk 3 Tablespoons Vanilla 2 Cups Sugar 1 Small Dewar 1 5-Liter Dewar 5 Liters of Liquid Nitrogen Balloons Racquet Balls Ping Pong Balls Tongs Styrofoam or Plastic cups Spoons Napkins

Safety

Liquid nitrogen can cause severe burns. All participants in these experiments must wear goggles at all times. Anyone touching the metal bowl must be wearing cryogloves. Only experienced adult scientist should dispense the liquid nitrogen.

History

Folk tales claim that the cook of the French king Charles I was the first to invent ice cream in the early 1600s. Charles was so pleased that he wanted the recipe to be kept a secret, so the dessert could only be served at his table. The cook did not keep his promise of secrecy, and the recipe for ice cream spread widely.

What To Do

Conversion of gaseous nitrogen to liquid nitrogen. Blow into a balloon until it is approximately four inches in diameter. Fill the small dewar with liquid nitrogen. Place the balloon in the dewar. Cover the dewar and let the balloon remain there for 15 20 minutes. Use tongs to remove the balloon. Observe the balloon for a few minutes.

Questions

1. What is observable in the bottom of the balloon? 2. What happens as the balloon warms to room temperature?

Summary

The air inside the balloon was cooled enough by the liquid nitrogen to change from gas to liquid. As the balloon warms up and begins to expand a small amount of liquid air should be visible inside the balloon. Since air is mostly nitrogen it is mostly liquid nitrogen that can be seen inside the balloon. The volume change associated with the phase change from gas to liquid is dramatic because the molecules in liquids are so much closer together than in gases.

Changing the Properties of a Racquet Ball

Have a student bounce a racquet ball. Use tongs to place the racquetball in a dewar of liquid nitrogen. Allow it to remain there for 5 minutes. Ask students what will happen when the ball is removed and bounced again. Use tongs to remove the racquetball from the dewar. Away from the students, but still in their view, drop the ball on the floor.

Question

1. Why did that happen to the ball?

Summary

The racquetball at room temperature bounces easily, but when it is cooled to liquid nitrogen temperature it becomes very hard and brittle. When dropped to the floor the ball shatters like glass.

Liquid Nitrogen and Ping Pong Ball Behavior With a small pin puncture a ping-pong ball by pushing it into the ball at an angle. Cool the ping-pong ball by immersing it in liquid nitrogen for a few minutes. Use tongs to carefully dunk the ball under the surface of the liquid. Use tongs to move remove the ping-pong ball and place it on a table or some other smooth surface. Observe carefully as the ball begins to warm up.

Questions

1. What is observable in the bottom of the balloon? 2. What happens as the balloon warms to room temperature?

Summary

Conversion of Gaseous Nitrogen to Liquid Nitrogen

Blow into a balloon until it is approximately four inches in diameter. Fill the small dewar with liquid nitrogen. Place the balloon in the dewar. Cover the dewar and let the balloon remain there for 15-20 minutes. Use tongs to remove the balloon. Observe the balloon for a few minutes.

Questions

1. What is observable in the bottom of the balloon? 2. What happens as the balloon warms to room temperature?

Summary

Source

Light Sticks

Index

There are many different sources of light, including a variety of chemical reactions that produce light. Combustion reactions produce light and heat, but some chemical reactions give off light without heat. Chemiluminescence is the light produced by these nonthermal chemical reactions. This experiment introduces chemiluminescence and investigates the effect temperature changes have on the intensity of the light.

Materials

3 light sticks of the same color Container of hot water (no warmer than 70 oC) Container of cold water

What To Do

Activate one light stick by bending the plastic enough to break the glass vial inside. Pass it around so everyone can feel that heat is not being produced with the light. Activate the other two light sticks. Place one in the container of cold water and the other in the container of hot water. Keep the first light stick at room temperature as a control. After a few minutes remove the light sticks from the water and compare the intensities with that of the control. Place the light stick that was in hot water in cold water and place the one that was in cold water in hot water. After a few minutes remove the light sticks from the water and compare the intensities.

Questions

1. Once activated, do light sticks increase, decrease, or remain the same temperature? 2. Did increasing the temperature of the light stick increase or decrease the intensity of light? Why? 3. When the temperatures of the light sticks were reversed did the intensities reverse? If so, how long did it take?

Summary

Some chemical reactions produce light without producing heat. The light produced by these reactions is called chemiluminescence. The light sticks consist of two solutions enclosed in a plastic tube. Phenyl oxalate ester and a fluorescent dye make up one solution. The other solution, dilute hydrogen peroxide, is sealed in a glass vial inside the plastic tube. When the light stick is bent to activate it the vial of hydrogen peroxide is broken so the two solutions can react. The chemical reaction gives off energy as light, or chemiluminescence. Since the light is produced by a chemical reaction and most chemical reaction rates are affected by temperature, a change in light intensity with a change in temperature is expected. Generally the rate of a reaction increases with increasing temperature. For this reaction, an increase in the reaction rate results in an increase in light intensity. This is easy to see when the light sticks are placed in hot and cold water.

Extension

Chemiluminescence in living creatures is called bioluminescence. Coleptera Lampyridae beetles, better known as fireflies or lightning bugs, use a chemical reaction within their bodies to produce light. Model lightning bugs can be made in the classroom using light sticks and a few craft supplies.

Source

“Teaching Physical Science through Children’s Literature Fireflies!” Julie Brinckloe. ISBN 0-689-71055-0 S. Olesik, WOW Project, Ohio State University, 2002.

pH Values of Common Materials 1.0 battery acid (sulfuric acid) 1.8-2.0 limes 2.2-2.4 lemon juice 2.2 vinegar (acetic acid) 2.8-3.4 fruit jellies 2.9-3.3 apple juice, cola 3.0-3.5 strawberries 3.7 orange juice 4.0-4.5 tomatoes 5.6 unpolluted rain 5.8-6.4 peas 6.0-6.5 corn 6.1-6.4 butter 6.4 cowâ&#x20AC;&#x2122;s milk 6.5-7.5 human saliva 6.5-7.0 maple syrup 7.0 distilled water 7.3-7.5 human blood 7.6-8.0 egg whites 8.3 baking soda 9.2 borax 10.5 milk of magnesia 11.0 laundry ammonia 12.0 lime water 13.0 lye 14.0 Source

CRC Handbook of Chemistry and Physics S. Olesik, WOW Project, Ohio State University, 2002.

Index

Supply Lists Acid-Base Chemistry

Chemical and Physical Changes Water Vinegar Hydrogen Peroxide (3% solution) Epsom salt Baking soda Alka-Seltzer tablets Potato Powdered laundry detergent Empty film containers Ice Boiling water Beakers or clear plastic cups

Chromatography: Food Coloring

Chromatography: Grape Soda

Chromatography: T-shirts 100% cotton T-shirt Prang markers Water Plastic wrap Plastic tub

Light Sticks

3 light sticks of the same color Container of hot water (no warmer than 70 oC) Container of cold water

References

Index

“Chemical Demonstrations: A Handbook for Teachers of Chemistry.” Vol. 3., Bassam Shakhashiri, University of Wisconsin Press, 1989. “Solids, Liquids and Gases.” The Ontario Science Centre, Kids Can Press, 1998. “Science Is.” Susan V. Bosak, Scholastic Press, 1991. “The Best of Wonder Science.” Ed. Jay Whitney, Delmar Publishers, 1997. “Teaching Physical Science through Children’s Literature Fireflies!” Julie Brinckloe. ISBN 0-689-71055-0 “T-shirt Chromatography.” J. M. Buccigross, J. Chem. Education, 978- 979 (1992). CRC Handbook of Chemistry and Physics. M. Bailey, The Ohio State University. WOW Staff, 2002.

Children’s Literature

Index

“The Magic School Bus Gets Baked in a Cake: A Book About Kitchen Chemistry.” By Linda Beech, illustrated by Ted Enik. Book adaptation of an episode of the animated TV series The Magic School Bus, based on the series by Joanna Cole and Bruce Degan. Scholastic, Inc.: New York, 1995. ISBN 0-590-22295-3. “Science Project Ideas About Kitchen Chemistry.” By Robert Gardner. Enslow Publishers, Inc.: Berkeley Heights, 2002. ISBN 0-7660- 1706-0. “Acids and Bases.” By J.M. Patten. The Rourke Book Co., Inc.: Vero Beach, 1995. ISBN 1-55916-128-0. “The Atoms Family.” By J.M. Patten. The Rourke Book Co., Inc.: Vero Beach, 1995. ISBN 1-55916-125-6. “Elements, Compunds, and Mixtures.” By J.M. Patten. The Rourke Book Co., Inc.: Vero Beach, 1995. ISBN 1-55916-127-2. “The Usborne Illustrated Encyclopedia: Science and Technology.” Usborne Publishing: London, 1996. “The Usborne Internet-Linked Library of Science: Materials.” By Alastair Smith, Phillip Clarke, and Corrine Henderson. Usborne Publishing: London, 2001. “The Usborne Internet-Linked Library of Science: Mixtures and Compounds.” By Alastair Smith, Phillip Clarke, and Corrine Henderson. Usborne Publishing: London, 2001. “Janice Van Cleave’s Molecules: Mind-boggling Experiments You Can Turn Into Science Fair Projects.” By Janice Van Cleave. John Wiley & Sons, Inc.: New York, 1993. ISBN 0-471-55054-X.

Notes

Index

There are currently no notes on this unit. If you have suggestions or changes to make on the experiments or units, please email us! Our address is wow@chemistry.ohio-state.edu. S. Olesik, WOW Project, Ohio State University, 2002.

Copyright ÂŠ 2002-2010 by S.Olesik, Wonders of Our World Project (WOW), the Ohio State University. Permission to make digital or hard copies of portions of this work for personal or classroom use is granted without fee provided that the copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page in print or the first screen in digital media. Abstracting with credit is permitted.