Science Thursdays

2nd Thursday of the Month

Join Dr. Lisa Chirlian the Second Thursday of each month as we explore Kitchen Chemistry - and play Science Fact-or-Fiction; where you can win the greatest prize of all... the prize of knowledge!

Chemistry In Your Kitchen!

Chemistry is the study of the way materials are put together and how they act under various conditions and best of all - - chemistry is ALL around us! Did you know that you have a chemistry lab right in your own home? These experiments use everyday materials and can be performed in an ordinary kitchen. Before we begin, there are some General Safety Rules to learn.

• Always be sure to have a responsible adult supervising your experiment - in fact, make Kitchen Chemistry a family experience!
• Never taste food that you are using for a science experiment - not only might it taste bad, it could also be bad FOR you.
• Finally, as a general safety precaution, never mix bleach or ammonia with anything else!

Now that you have those rules - let's learn about chemistry!

Fun With Ice

Here’s a magic trick you can do to amaze your friends! You can lift an ice cube without tying any knots! Unlike most magic tricks, which use illusions, this one uses science.

Magic Trick Materials

String
Ice cube
Salt (in a shaker works best)

1) Put the ice cube on a plate. Put a little bit of water on top of it.

2) Cut a piece of string (about 6 inches long). Put one end of the string in the water on the ice cube. Show everyone that the string is not attached to the ice cube.

3) Sprinkle a little salt on top of the ice cube. If you want to be mysterious, you can tell everyone that it is magic powder. If you want to be scientific, you can explain that the salt will melt a little bit of the ice so the string sinks into the cube. Then the coldness of the cube will refreeze the water around the string.

4) Wait a minute or so (it’s a good idea to practice this beforehand, so you know how long it will take). You will probably be able to see the string sink into the ice a little bit.

5) Once you feel confident the string is in the cube, pick it up and amaze your friends!

Why does this work?  (And another experiment to try)

Almost everyone knows that water freezes (or melts) at 32oF (0oC).  That’s a physical constant, which means that under normal conditions, water always freezes or melts at this temperature.  But, we can do something to change the melting point of water.   In the winter ice forms on roads and sidewalks, making travel slippery and dangerous. When the temperature is below 32oF (0oC), ice will not melt by itself.  To make it melt, people put salt on the ice.  Adding salt to the ice lowers the freezing point of the ice (now an ice-salt mixture). 

You can see this for yourself, with this easy experiment.

Materials for observing the change in freezing point:

Insulated cup (Styrofoam or double walled travel mug—a regular cup will work, just not as well)
Water
Ice
Salt
Thermometer (Be sure you have one that can read temperatures below freezing!)

1) Fill your glass, about 2/3 full, with ice.  Add cold water, leaving some room at the top (so you can stir the solution).

2) Wait a few minutes (keep stirring gently) and then measure the temperature.  It should be 32oF(0oC).  If it is not, you may need to either wait a little longer or add more ice. 

3) Add salt to the ice/water solution.  You will need to add a lot (1/4 to 1/2 cup, or more, depending on the size of your cup).  You want the solution to be very salty.

4) Wait a few minutes and measure the temperature again.  How low did it go? 

5) If the temperature of the solution only went down a few degrees, add more salt and measure again! 

Crystal Snowflakes

Last month I explained how to grow sugar crystals to make candy. This month, we are also going to grow crystals only we are going to make them look like snowflakes. Snowflakes are crystals of water. Since water needs to be kept cold to stay solid, you can’t really use water crystals to make things to keep inside.

You need to use other compounds, which are solid at room temperature (like sugar) to make things to keep. For this experiment, we are going to use borax. You can find borax in the laundry aisle of many supermarkets. One brand names is 20 Mule Team. Caution: This experiment uses boiling water which is very hot. Please be sure to have a responsible adult supervising. Also, be sure to wash your hands after working with borax and keep the snowflakes away from small children or pets that might try to eat them!

Materials:

1 cup boiling water
2-3 tablespoons borax
Shallow pan or jar
Pipe cleaners

1) Create your borax solution. Boil one cup of water. Little by little, stir the borax into the water (about a half tablespoon at a time). Keep stirring until no more borax will dissolve.

2) Create your snowflake form. Cut a pipe cleaner into three pieces and twist them together in the middle. If you want to grow your snowflake in a jar, make one piece longer so you can attach it to a pencil and hang it into the jar.

3) Put your snowflake form(s) into the jar or pan. Pour the borax solution on top. Put them in a place where you can check on them daily.

4) When your snowflakes have grown, take them out and let them dry. If you hang them near a sunny window, they will sparkle!

Things to Think About and Do

- Look at the crystals with a magnifying glass. Compare them to the borax powder you started with... do they look similar or different?
- Can you grow other kinds of snowflakes? You can try this same experiment with sugar, table salt or Epsom salts. Which grows the biggest snowflakes?

Growing Sugar Crystals

This is not an experiment—because you can eat the results. This is a cooking project which shows how science is part of our lives—even candy! Sugar is a solid. Each little grain or crystal of sugar is made up of lots of individual sugar molecules. The molecules are arranged in a very orderly fashion that gives sugar its shape. Rock candy is made of sugar crystals. The crystals grow bigger than the ones you find in a packet of sugar or the sugar you buy to make cookies. They’re easy to grow—just give it a try! Caution: The sugar/water solution is extremely hot. Please take care when mixing and pouring it.

Materials:
Remember—you’re going to eat the results—don’t use anything that you wouldn’t use for food preparation)
3 cups sugar
1 cup water
Heavy saucepan
Clean jars or tall glasses
Clean string, straw or popsicle stick

1) Get your crystal growing apparatus ready. You need to suspend your string into the container without it touching the sides or bottom. If you are using a string, you can tie it to a pencil and then lay the pencil across the top of the jar like shown in this image.

Wet your string and dip it into sugar so that a few crystals cling to the string. This will give your candy a place to start growing.

2) Put three cups of sugar in the pan and add 1 cup of water. It will seem like there is too much sugar/not enough water, but it will be ok! Put the pan on the stove and heat the sugar/water solution. Stir it gently. As the solution heats up, more and more sugar will dissolve. The solution will look cloudy. You want to heat it until the solution turns clear and starts to bubble. Be Very Careful—the solution is very hot. Let it cool for 5-10 minutes before proceeding.

3) Pour the solution into the jars. Be sure the string is not touching the sides or bottom. Growing crystals takes time because the crystals grow as the water evaporates. Cover the top with a paper towel or coffee filter to prevent dust from getting into the jar. Put the jar some place where it won’t be disturbed.

4) Check on your crystals every day. If a crust of crystals forms across the top of the jar, just remove it with a fork or spoon so water can continue to evaporate. If crystals form on the sides/bottom of the jar, pour the solution into a clean jar and place the string into the clean jar.

5) When your candy is big enough, you can take it out and eat it. If you want to save it, just let it dry and then store it in a closed container. It won’t spoil, but if you leave it out, it may attract bugs! Enjoy!

Watching an Enzyme Work

Plants and people need lots of chemistry to live! Our bodies are chemical plants using food and oxygen in chemical reactions to do all the wonderful things we do every day. Our bodies use special molecules, called enzymes to make these reactions go smoothly and quickly.

Catalase is a common enzyme. It helps change peroxides (which are created in other reactions and aren’t good for living things) into water and oxygen. It does this very quickly. Most living tissue contains catalase. We can use potatoes to help see catalase work because bubbles of oxygen form when we put potatoes into hydrogen peroxide. We can also see how to stop enzymes from working.

When potatoes are cooked, the structure of the enzyme changes and it doesn’t work. Cooked potatoes won’t make bubbles of oxygen. Even though catalase is present in living things, the amount may vary. Apples contain very little catalase . Putting apples in peroxide causes only a few bubbles to form.

Materials
Hydrogen Peroxide (available in the first aid section of most pharmacies or supermarkets)
Potatoes
Apples
Plastic cups
A small pot (for cooking some of the potato)

1) Label the cups: a. Hydrogen peroxide plus raw potato b. Water plus raw potato c. Hydrogen peroxide plus cooked potato d. Hydrogen peroxide plus apple

2) Cut small pieces of potato. Leave some raw. Boil some pieces for 5-10 minutes (until they are soft)
3) Cut small pieces of apple.
4) Put a small amount of hydrogen peroxide or water (as labeled) into each cup.
5) Add raw potato to the cup with hydrogen peroxide and the cup with water. What happens in each cup?
6) Add cooked potato to the cup with hydrogen peroxide. Does it behave like the raw potato?
7) Add the apple to the hydrogen peroxide. Do you see any bubbles? Look carefully, especially around the apple pieces.
8) Try this! Put other fruits or vegetables into the peroxide (try carrots, mushrooms, grapes or zucchini). Which ones make lots of bubbles?

Making a Lava Lamp

You probably have seen Lava Lamps in stores. These lamps plug into the wall and can get rather warm. They contain materials that are unsafe to use at home. Here's a simple way to make a lava lamp using materials you can find in your kitchen.

Materials
A clear bottle
water
cooking oil
table salt
food coloring (optional)

Fill the water about two-thirds full of water. Add a drop or two of food coloring, if you want. Pour about an inch or two of oil on top of the water and let the oil settle on top of the water. Pour a stream of salt on top of the oil and watch your lamp go! Keep adding salt to keep the lamp moving.

Making Glue from Milk

Most people buy glue at the store to use when they need to stick things together. Store bought glue is convenient, but for fun, you can make your own glue from milk. It’s fun and it’s easy.
Just follow these steps.

Materials
Skim milk (do not use whole or 2% milk)
Vinegar
Coffee Filter Paper (cone type works best)
Paper Towels
Baking Soda

Procedure

Mix 1 cup of milk and ¼ cup of vinegar. Let the mixture sit for 10-15 minutes. The milk will separate and small pieces of a white solid will form. This white solid is some of the proteins in milk (casein) and will end up becoming the glue.

Place the coffee filter paper over a tall glass. Pour the milk/vinegar mixture into the filter. Pour a little bit at a time so the mixture doesn’t overflow the filter. Make sure the bottom of the filter is above the level of liquid in draining into the glass. Let the filter sit for 10-15 minutes so most of the liquid is removed.

Pour the solids into a clean bowl or plastic container. Add two teaspoons of baking soda to the solids and mix. Listen carefully—you will be able to hear the baking soda react with the extra vinegar and you may even see the some bubbles. Add about one teaspoon of water and mix. You’ve made glue. Now try it out on some paper!

Why does it work?

Milk is a suspension—solids are suspended in the liquid (not dissolved like in salt water). When you add vinegar (an acid), some of these suspended solids (the protein, casein) change their shape and can no longer be suspended. The casein forms the gloppy solid that is filtered from the liquid. Baking soda (a base) is then added to neutralize the acid and change the protein back into a shape that is more fluid. This becomes the glue. Water can be added to give the glue whatever consistency you would like.

Separating Dyes in Water

Sometimes, people want to know what is in a mixture. Scientists use a process called chromatography (kroh-muh-tog-ruh-fee) to separate different parts of a mixture. Dots of the mixtures—different colors of washable markers—are placed on a piece of coffee filter paper. The end of the paper is put into water. As the water moves up the filter paper, it carries the dye from the marker. Different dyes move up the paper at different rates and become separated. While this may sound very complicated, it’s actually an easy process to do at home.

Materials

Paper cups
Coffee Filters (cone type)
Water-soluble markers (marked washable)
Pencil
Binder clip

Procedure

1. Put a small amount of water in the bottom of a paper cup.  The water should come up about one quarter inch from the bottom of the cup.

2. Cut the coffee filter paper into rectangles approximately one half inch wide by four inches long.

3. Place a small spot of marker approximately one half inch from the bottom of the paper.  The spot should be above the level of the water in the cup. 

4. Use a binder clip to attach the filter paper to a pencil, so that the top of the paper is attached to pencil and the bottom hangs free. 

5. Place the pencil across the top of the glass so the bottom of the paper is immersed in the water.  Be sure that the spot of marker is above the level of the water and that the paper doesn’t touch the sides of the cup. 

6. Watch as the water moves up the paper.  The spot of color will start to move up the paper as well.  If the marker is a mixture of dyes, the different colors will start to separate. 

Things to think about

Did the colors separate the way you expected? 

Which colors separated the most?  The least? 

If you have several different sets of markers, try different shades of one color (greens and purples work well).  Do the shades separate with the same pattern? 


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Finding Starch Around The Kitchen

Starch is a part of many foods we eat. It’s not always easy to know what foods contain starch. Sure, cornstarch is easy to identify because it has starch in the name. But does sugar contain starch? Does flour? Here’s a fun way to find out.

First, go to your local drugstore and get some iodine solution. Iodine is sold as an antiseptic (cleans things) and can usually be found in the first aid section. Ask your local pharmacist if you can’t find it.

Then, gather up some foods from your kitchen. Remember, when doing science in the kitchen—never, ever eat the food you are using and keep your work away from surfaces where food is prepared. The sink can be a good place to work.

Put a little bit of each food in a small disposable cup. If you prefer, you can put several types of food on a disposable plate. Be sure to leave enough room between the different samples.

Look at the iodine solution. The color ranges from orange to brown, depending on how much you have in your container. Place a few drops of iodine on each sample. If the sample doesn’t contain starch, the iodine solution will remain the same orange/brown color. But, if the sample contains starch, the iodine solution will turn purple/black in color.

After you test all your samples, try to figure out what starch containing compounds have in common. Do they come from animals or plants? Do they come from certain parts of an animal or plant? You might decide to analyze some new, different foods to figure it out.

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Making Slime

Slime can be made using white glue and borax (found in the laundry detergent section of most supermarkets). When you make slime you start with a polymer (the glue). Polymers are molecules that form in long chains. The borax links the individual chains together and changes the properties of the glue.

If you make slime, ask yourself what happens to the slime when you stretch it by pulling your hands away from each other? What happens to the slime if, instead of pulling your hands away from each other, you pull one hand toward your body and push the other hand away?

Make a saturated Borax solution
• Add 1 tablespoon of Borax to 1 cup of water.
• Stir well. If you have a jar or other suitable container, shake the mixture.
• The borax will settle to the bottom, at first, but with stirring will create a cloudy solution. It’s OK if a little borax remains—you are creating a saturated solution, which means that you have the maximum amount of borax, dissolved.

Prepare the glue solution
• Measure ½ cup of glue
• Add ½ cup of water, stir to combine
• Pour ½ cup of the glue/water mixture into a Ziploc bag.
• Food coloring may be added now (if you want colored slime!)

Make Slime!
• Put some of the Borax solution into a cup.
• Add a bit of the Borax to the glue (you can start with about ¼ cup). Seal the bag and knead the mixture gently.
• Add more Borax (up to ½ cup) until the slime has the right consistency.
• When you are finished, tTake the slime out of the bag and have fun!

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Making Oobleck

In the book, "Bartholomew and the Oobleck" by Dr. Seuss, the king of Didd wishes for something different to fall from the sky than rain or snow. Though no one is prepared for a sudden shower of Oobleck! Now you can make your own magical messy Oobleck at home.

Oobleck is similar to slime except it is made from cornstarch (also a polymer) and water. Investigate ooblek’s properties and try to decide if it is a solid or a liquid!

Materials Needed
* 2 cups of cornstarch
* 1 cup of water
* Green food coloring
* Sheet of wax paper

Mix together the cornstarch, water, and food coloring in a bowl. Pour a little onto the wax paper so you can play with it. Roll it between your hands and it feels solid, but let it sit and it becomes a gooey liquid.

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Using Baking Soda To Find Acids

Some of the things we find in kitchens are acids. Acids are found in foods that taste sour. Here is a way to use baking soda to identify acids in the kitchen. When baking soda is mixed with an acid, bubbles of carbon dioxide form. If baking soda is mixed with a base or a neutral (neither an acid nor a base), no bubbles form.

Materials Needed
* baking soda
* water milk
* vinegar
* fruit juices (for example, lemon, pineapple, orange, apple)
* liquid soap
* several small cups

Place about a teaspoon of baking soda in each of the small cups. Add some of each liquid to the baking soda. If bubbles form, you've found an acid!

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Making An Acid/Base Indicator
With Cabbage Juice

Baking soda can only identify acids. You can use cabbage leaves to make an indicator (a substance which changes different colors in acids or bases). Cabbage juice is bluish and turns red in acids and green in bases.

Materials Needed
* a few red cabbage leaves
* water
* milk
* vinegar
* fruit juices (for example, lemon, pineapple, orange, apple)
* liquid soap
* Milk of Magnesia
* several small cups (clear cups work best)

Rip the cabbage leaves into small pieces. Place in a pan and cover with water. Heat the water until it boils and then turn down the heat. Let the cabbage leaves simmer for 10-15 minutes. Let cool. Strain the leaves out of the juice. Put the juice in each of the small cups. Add some of each liquid to the cabbage juice and watch the color change!

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Making Invisible Ink

You can make several different kinds of invisible ink in the kitchen. Lemon juice and milk both become visible when heated. A solution of baking soda and water becomes visible when grape juice is painted over it.

Materials Needed
* lemon juice
* milk
* baking soda dissolved in water
* purple grape juice
* Q-tips
* white paper

Use a Q-tip to write a secret message with lemon juice. Let it dry. Get an adult to help you go over the paper with a warm iron. The message will appear in brown. Try the same thing with milk. Use a Q-tip to write a secret message with the baking soda solution. Let it dry. Paint over the message with grape juice. The grape juice will change color and show your message.

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