real science for today's homeschooler

Using Popcorn to Practice Scientific Method

Using Popcorn to Practice Scientific Method

This is a fairly common science fair project that I actually helped my grandson carry out for an elementary science fair. It’s definitely not a new idea, but a great way to let children work through the scientific method using a fun topic . . . POPCORN! The question to be answered is: “Does storage temperature affect how well popcorn pops?” Children will be storing popcorn in a warm environment, room temperature, cold, and frozen. Before beginning the experiment, encourage students to make a Hypothesis. Ask them to decide which storage method they think will work best, and why.

Materials: large bag of loose popcorn (not the individual “flavored” bags), baggies, paper lunch sacks, access to a microwave

Here’s the procedure we used, but it’s important to let your child come up with the procedure if this is to be a scientific method experiment.

1. Put 100 popcorn kernels in a plastic baggie and label as “warm.” Repeat with 3 more baggies, labeling them as “room temperature,” “cold,” “frozen.”

2. Place the baggies in the appropriate area. For example, store the “warm” bag under an electric blanket, the “room temperature” bag in the pantry, the “cold” bag in the refrigerator, and the “frozen” bag in the freezer. Select a specific time for storage, such as a week, a month, etc.

3. After the storage time is complete, remove the bags from their storage area at the same time. To test the storage methods, divide out the 100 popcorn kernels between 5 paper lunch sacks, with 20 kernels in each bag. Label each paper sack with the appropriate storage method. Repeat with all the remaining popcorn, being sure to label each paper sack with the correct storage method!

4. Decide on a specific popping time. Somewhere around 2 minutes works best, but any time will work if it gives the popcorn time to pop and you keep the time the same for all trials.

5. Put one of each sack of popcorn into the microwave at the same time. (In other words, place one sack that contains popcorn stored as “warm,” one sack with “cold” popcorn, etc. Turn on the microwave for the specified time. After the time has elapsed, remove the bags and count the number of kernels that popped. Record. Repeat until all the popcorn has been tried.

Data: Here’s a sample data table that can be used to record the results. For older children you may want to let them design their own table.

  Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Average
warm            
room            
cold            
frozen            

 

Older children can find the average of each type. For younger children who may not understand the concept of averaging, change to “Total” for the last column.

Analysis: Younger children can compare the totals to see which storage method resulted in more popped kernels. Older children can graph the results for a visual representation.

Conclusion: Have students state out loud, or write down, which storage method produced the most popped popcorn. Why do they think this method worked best? Also have them refer back to their original hypothesis. Was their hypothesis right or wrong?

HINT: Based on experience, don’t try to pop one bag at a time in the microwave. There will not be enough water in the popcorn to absorb the microwaves and the appliance will overheat! Mine actually stopped working for awhile! Popping four bags at a time worked well for us, but do feel the sides of the microwave after the first round to make sure it isn’t overheating. Take breaks between rounds if needed.

ALTERNATE METHODS: Children can also come up with their own idea of what to test, such as light vs dark, storage time, type of storage container, etc. The more children are able to make the experiment their own, the better!

BACKGROUND: Depending on the age of your child, You may also want to have them research WHY popcorn pops. Here’s a great website that explains the science of popcorn, as well as some interesting history: http://www.popcorn.org/Facts-Fun/What-Makes-Popcorn-Pop.

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

How do you rate in general Scientific Knowledge?

How do you rate in general Scientific Knowledge?

Here’s an interesting Science Quiz done by the Pew Research Center. It contains some basic science knowledge questions in multiple choice format. Take the quiz and then see how you score against average American adults. You can also find overall results based on demographics. Follow another link to check out the full analysis of the poll that was designed to discover, “What the Public Does and Does Not Know About Science.”

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Separating a Mixture

Separating a Mixture

A mixture contains two or more substances that are not chemically combined. Each substance retains its original properties, and can be separated by physical means. Challenge your student to design a method to separate a mixture into its separate components.

First, you’ll need to make the mixture that will be separated. A suggestion would be to mix salt, sand, pebbles, and iron filings. Home improvement stores sell “play sand” which works well for many science experiments, and you can order iron filings from the internet. The base of your mixture should be sand, then add the other substances in slightly smaller quantities.

Here are the steps of the experiment:

1. Have your child observe the mixture and guess the substances from which it is made.

2. Explain the scientific definition of a mixture and give your child a sample of each of the individual substances in the mixture.

3. Ask your child to brainstorm the physical properties of each of the individual substances. (If they don’t come up with these on their own, lead them to include that salt dissolves in water, pebbles are much larger than the other ingredients, and iron is magnetic.)

4. Ask your child to brainstorm how the physical properties of the substances could be used to separate each from the mixture. Depending on the age of the child, you may or may not have to help with this step. You can also lead them to experiment with the individual substances by seeing which will dissolve in water and which are attracted to a magnet, etc.

5. Once your child has developed a plan to separate the mixture, help them carry it out. Here are a few suggestions to successfully separate the four ingredients:

PEBBLES – Separate the pebbles either by picking them out individually with tweezers or fingers, or by straining them out. A colander or a piece of window screen works well as a strainer.

IRON FILINGS – The small iron fragments can easily be pulled from the mixture with a magnet. To keep the magnet clean, put it inside a plastic baggie. After you have collected the iron filings on the outside of the bag, pull the magnet away from the plastic and the filings will be released.

SALT – Pour the mixture into a container of water and stir well until the salt has had time to dissolve completely. Pour off the water. To demonstrate that the procedure worked, evaporate the water to reveal the salt left behind.

SAND – Once the other three ingredients have been removed, the (wet) sand will be left behind.

6. Emphasis that your child has proven that the original material was a mixture because the individual parts were separated by physical means.

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Testing the pH of Soap

Testing the pH of Soap

We usually think of soap as being a very mild substance that is good for the skin. But, the cleansing effect of soap is due, in part, to the fact that it is a basic substance. Some soaps can dry out the skin, or even damage skin with frequent use.

When you teach your children about acids and bases and the pH scale, have them explore the pH of different soaps in your house. Test bath soap, dish soap, clothes soap, shampoos, facial cleansers, etc. They can also test household cleaners you may use, especially those that contain ammonia. But be sure these harsher products are tested under adult supervision since ammonia products can be harmful if they get in the eyes or are swallowed.

The easiest way to test pH is with pH test strips. You can buy these anywhere swimming pool or pond chemicals are sold, but they are usually fairly expensive. Unless you want them right away, you can order universal pH paper strips here for a very reasonable price. The shipping is a flat rate so you might want to join with other homeschool families to put in one order together, or look around for other science supplies you might need in the future.

For thick liquid soaps, powders, or bar soap, mix with a little distilled water so that the test strips can absorb the chemicals. All pH test strip packages come with a color key that can be used to determine the pH. Very often the color of the test strip will be in between two colors on the key. Use this as an opportunity to teach your children about estimating between two known values.

After you have results, remind children that a pH of 7 is “neutral” and completely harmless. The farther away from 7, the more harsh, and potentially harmful the base. Discuss the relationship between the pH of different types of soaps and their intended use. Why is there such a difference between bath soap and household cleaners? Also, check to see if any of the products advertise themselves to be “pH balanced.” Based on the pH test results, what does that mean? Do those products have a different pH from other similar products that don’t make that claim? Finally, you can extend the results with a consumer finance application. Do you find a difference in the pH of similar products from different brands? For example, is there a difference between the pH of a name brand bath soap and a cheaper store brand?

One final word about using test strips. A universal test strip tests a wide range of pH values and so will have less of a color change between similar pH values. A more narrow range test strip will show a bigger color range between similar pH values, but will show no results outside of the range of the pH paper. So, if you buy narrow range test strips, be sure they are within the range you want to test. For example, if you are testing soaps you will need to use pH test strips that test for a pH range above 7. Acid test strips (that test below 7) will give no results when testing soaps.

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Invisible Ink as a Chemical Reaction

Invisible Ink as a Chemical Reaction

Kids love spy gadgets and mystery! Use homemade invisible ink to write secret notes, then teach your child the science behind the process used to reveal the hidden messages.

There are many ways to make invisible ink. To use one of the safest methods, just use a Q-tip to write or draw on white paper with lemon juice. Actually, any fruit juice that contains citric acid will work, but lemon juice tends to dry the clearest, keeping the message hidden until revealed.

To reveal the message, the paper needs to be heated in some way. Whether or not your child can do this by themselves depends on the age of the child and the method used. Below are several ways to made the message visible. Choose the one most appropriate for your child:
1. Hold the paper over a candle. This is a slow method, requiring patience, as the candle can easily scorch the paper if brought too close.
2. Hold the paper over a hot light bulb. This method is very similar to the candle, but it does heat a larger area. The bulb must get very hot. For example, a 100 W incandescent bulb. Fluorescent bulbs won’t work. Care should be taken not to touch the bulb!
3. Carefully iron over the paper. Gives you a quick reveal but for safety, this needs to be done under direct parent supervision.
4. Heat the paper for about 5 minutes in the oven (around 350 degrees). Watch carefully to make sure the paper doesn’t overheat and burn. Again, direct parent supervision is needed for this method.
5. Hold the paper over a toaster. The hot air rising from the toaster should be enough to reveal the message.
6. Direct sunlight on a very hot day will sometimes be enough heat to bring out the hidden message.
7. I have heard that a very hot blow dryer will reveal the message, but I’ve never had any luck with this method.

Here’s the science behind the reveal . . . Paper is made of cellulose, a starch that makes up the body of plants. Cellulose is a tough, fibrous molecule made of many, many glucose (sugar) molecules connected in long chains. The acid in the lemon juice naturally breaks down the cellulose, separating the individual glucose molecules, which is a chemical reaction. Heat makes that process work even faster, as raising the temperature almost always increases the rate of a chemical reaction. The heat also caramelizes the sugars now in the paper, turning them a brown color. So, the brown message you see on the paper is actually caramel!

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Growing Crystals with Common Chemicals

Growing Crystals with Common Chemicals

Crystal growing is a fun activity for kids and it is relevant to several areas of science, such as chemistry, as well as mineral formation in geology. Schools often use commercial chemicals to grow crystals in the classroom, and these chemicals can be difficult, if not impossible, to purchase as an individual. Here are a few household chemicals that can be used to grow crystals at home:

Aluminum potassium sulfate (alum) can be purchased in the spices area of the grocery store. This alum is not pure, and crystals do sometimes turn out small. Purchasing a more expensive brand will often grow better crystals, but alum is fairly expensive.

Sodium borate (borax) can be purchased in the laundry section of many stores.

Calcium chloride can be purchased at home improvement stores and stores that sell chemicals for swimming pools. Even at a specialty store, this is a fairly inexpensive chemical to purchase.

Copper sulfate is the ingredient in products used to kill roots in sewer lines. You can find this at home improvement stores. Moderately expensive, but a container goes a long way. This chemical makes very large, beautiful blue crystals and is a favorite for crystal growing. But, do be careful with storage of the crystals as the chemical is poisonous and it can be mistaken for candy by young children!

Magnesium sulfate (epsom salts) can be purchased at a drug store or the pharmacy section of the grocery store. It’s fairly inexpensive.

Sodium chloride (table salt) grows very nice cubic crystals.

Sucrose (table sugar) is used to make “rock candy” crystals. There are quite a few recipes on the internet for making rock candy, and it is a favorite to make. However, these are the hardest crystals to grow, and it can be messy! I’ve tried this using several different methods and have never been very successful. If anyone has a good recipe and growing technique for making rock candy, please post! 🙂

How to grow crystals:

The trick is to make a supersaturated solution of the chemical. It’s best to start with distilled water, which can be purchased by the gallon at the grocery. Heat the water, slowly add the chemical, and stir until completely dissolved. In order to make a supersaturated solution, the water needs to be very hot and you have to dissolve as much of the chemical as possible. Continue to add the chemical a little at a time, dissolving thoroughly before adding more. When you finally reach the point where no more chemical will dissolve, pour the hot solution into the container you’ll use to grow the crystals. You can also add a little food coloring if you want to make colored crystals. Don’t add too much as you don’t want to dilute the solution.

It’s important to use a container with very smooth inside surfaces, like glass. Also, be sure to only pour in the solution that is completely dissolved. Let the undissolved chemicals settle to the bottom of the original container and don’t transfer the last bit of solution. Finally, suspend a string into the crystal growing solution to give your crystals something to grow around, and leave undisturbed. Depending on the chemical used, crystals usually begin to form within hours, but may take several days to grow larger.

Safety:

Take care with the finished crystals and store them appropriately. Copper sulfate crystals are especially poisonous if ingested. Whatever chemical you use, do read the product label for safety precautions. The same precautions should be taken with the finished crystals! Remember, many candies are made to look like crystals and small children may not be able to tell the difference.

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Cooking Up a Chemical Change

Cooking Up a Chemical Change

Chemical change can be a hard concept for children to understand. It’s much easier to explain a physical change. Water freezes into ice. The ice is still water and can be melted back into liquid water. Tear a piece of paper in half, and you still have the same paper. Both are physical changes. But how do you demonstrate chemical change?

The easiest example of a chemical change is burning a piece of paper. The paper turns to ask and becomes a new substance, much different from the original paper. But, what about other examples? Try baking! Spend some quality time with your child, make dessert, and teach science all at the same time!

A cake or cupcakes are probably the best desserts to use to clearly show a chemical change. Before getting started, collect all the ingredients that will go into the cake batter. You don’t have to make a “scratch” cake for this to work. Even if you’re only adding eggs, oil, and water to a cake mix, students can still observe the chemical changes.

Have your child observe all the beginning ingredients. Older children can make a written list of the physical properties (characteristics) of each of the ingredients. Do let them observe the ingredients directly . . . open the cake mix pouch, break the egg, etc.

Now, mix up the batter while letting your child help at a level appropriate for their age. While mixing ingredients, discuss changes that are taking place. Point out that even though they may look different, the ingredients are all still there and haven’t changed into anything else. For example, the egg is mixed in the batter, but it is still egg. Have your child observe the final raw batter. Point out that the batter is a “mixture” of ingredients, but none of them have been chemically changed.

Finally, add heat . . . bake the cake! Make observations of the ingredients after they have cooked together. Point out that one evidence of a chemical change is that you come out with a completely new substance that doesn’t look anything like the original. Going from cake batter to a fluffy cake will be a clear example of “forming a new substance” to your child. Also, ask your child what was needed to make the chemical change happen. Heat! Point out that many chemical changes require heat. The heat causes the original substances to recombine to form new substances. Who knew Chemistry could taste so good!

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Periodic Table Basics

Periodic Table Basics

If your child has already learned about the parts of an atom (proton, neutron, and electron) they can understand the basics of the periodic table. From a basic periodic table, a young student can find: 1) the abbreviation for the element’s name, 2) how many protons an atom of the element has, 3) how many neutrons an average atom of the element has, 4) the number of electrons a neutral atom of the element has. Use the information below to teach your child the basics of using the periodic table. Then, turn the Periodic Table into a game. Give “clues” to a particular element and have your child use the clues to identify the element. You’ll find few examples of element clues at the end of this post to get you started.

Here’s an overview of periodic table basics:

periodic tableThe one or two letter symbol in each box is an abbreviation for the name of the element. In the example on the right, the abbreviation for carbon is C.

The number that is always above the symbol is the atomic number of the element. The atomic number gives the number of protons in one atom of that element.

The number under the symbol is the atomic mass. It is the average number of protons plus neutrons found in one atom of the element. You can use that number to find the number of neutrons in an average atom. Just subtract the number of protons from the rounded atomic number and you will have the average number of neutrons in one atom of the element.

Finally, in a neutral atom the number of electrons is always the same as the number of protons. So, the atomic number also gives the number of electrons in a neutral atom of the element.

Element clues:

1. Which element has 80 protons?

2. Which element has 16 neutrons and 16 electrons?

3. Which element’s name is abbreviated Fe?

Continue using the periodic table to make clues as long as the game holds the student’s interest. The more they become familiar with the periodic table now, the less intimidating it will be in upper level science classes!

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

Red Cabbage as a pH Indicator

Red Cabbage as a pH Indicator

pH is a hard concept for younger children to learn. Add a little excitement to the subject of acids and bases by using a natural pH indicator. First, the science . . . an indicator is a chemical that “indicates” or shows the presence of a substance, usually by a color change. There are many pH indicators, each working for a different range on the pH scale. A wide-range indicator detects substances on the entire pH spectrum.

A safe and easy pH indicator for kids to work with is cabbage juice. When added to different household substances, it turns a wide range of colors, which children love! Here’s how to prepare the indicator: Pinch up the very red (purple) leaves of a red leaf cabbage. Put in water and boil until the reddish purple color comes out into the water. You can do this on the stove, but the microwave works well, also. A few hints . . . use a high cabbage to water ratio as you want the color as concentrated as possible. And, use soft water. If your water is naturally soft, tap water will work fine. But, if you live in an area with hard water, it’s worth the cost to buy some distilled water for this activity. Cool the cabbage juice before using. It will store for several weeks in the refrigerator.

Next, have your child collect different household liquids they want to test for pH. You can find a list of the pH of some common liquids here. You can also just search “pH of ???” on the internet to find the pH of just about anything. Testing liquids from a wide range on the pH scale will give the most colorful results.

Once you have all your test liquids, add about a tablespoon of each to a test tube. (If you don’t have test tubes at home, the cups of a white egg carton work great!) Then, add a teaspoon or so of the cabbage juice indicator to each test liquid. The amount isn’t critical. Just add enough cabbage juice to get a good color change.

For older children, make a list of the test solutions and their actual pH collected from the internet. Have your child create a color scale that can be used to determine the pH of an unknown substance. For example, here’s a pH scale for another commercial indicator:pH scale

Once your child has made a pH chart for cabbage juice indicator, provide him/her with several “unknowns” to test the accuracy of their chart.

Share this on...Email this to someoneTweet about this on TwitterShare on Facebook