real science for today's homeschooler

Cloud in a Glass

Cloud in a Glass

As you’re studying weather, take a few minutes to make a cloud in a glass to help explain the process of condensation and cloud formation.

What you’ll need: clear glass or jar, kitchen matches, ice cubes, small plate or pan that will completely cover top of glass or jar (metal works best), boiling or very hot water

Procedure:
1. Fill the plate or pan with ice cubes and have it ready to quickly place over the top of the glass when needed.
2. Pour enough boiling water into the glass or jar so that there is about 1/2 centimeter of water covering the bottom.
3. Light a kitchen match and hold it inside the top of the glass for a minute or so. Right before the flame reaches your fingers, drop the match into the water in the glass.
4. Immediately, cover the top of the glass with the pan containing ice cubes.
5. Watch a “cloud” form inside the glass!

What’s Going On?
The boiling water has enough heat energy to cause some of the water molecules to evaporate and turn into water vapor inside the glass. Those individual water molecules will stay in a gas state as long as they have enough energy. When the pan of ice is placed over the top of the glass, heat energy from the water vapor molecules is transferred to the bottom of the cold pan. The water vapor molecules no longer have enough energy to remain in a gas state, and they condense back to a liquid state. The smoke from the burning match is made of tiny particles which remain suspended in the air inside the glass. As the water molecules began to condense, they collect around the smoke particles, forming the tiny water droplets that make the “cloud” in the glass.

How do Real Clouds Form?
Clouds in Earth’s atmosphere form in pretty much the same way. As the Sun’s energy heats water on the surface of the Earth, it evaporates. As the moist air continues to heat up, it begins to rise higher into the atmosphere. Earth’s atmosphere gets colder and colder the higher up you go. When the water vapor in the rising air gets cold enough, it condenses around “condensation nuclei” in the atmosphere. Condensation nuclei are tiny particles of dust, salt, and other solids that are suspended in the air, similar to the smoke from the match. When enough tiny water droplets form in the atmosphere, we see a cloud in the sky!

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

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

Earthquake Waves

Earthquake Waves

The general properties of waves can be investigated through an activity on earthquakes. First, have your child research the three different types of earthquake waves. Encourage them to find the following information about each wave:

1. name of the wave

2. how quickly it travels compared to the other two

3. what part of the Earth does it travel through

4. type of wave, based on motion (compression wave, transverse wave, etc.)

5. does it cause damage to buildings

Help your child organize the information they find into a chart or data table. This can be done on the computer or by hand. Or, make a poster and add pictures and drawings. Use the chart to compare and contrast the three types of earthquake waves.

Next, have your child build a structure that will withstand the different types of earthquake waves. (Encourage them to look at the type of motion caused by each wave.) Use any type of materials such as building blocks, boxes, DVD cases, etc. In order to test their construction, have them build it on a surface that will be easy to move, such as a small table, board, etc.

Test the structure(s) by recreating the various motions of the different earthquake waves:

P waves – move the surface back and forth in a horizontal motion

S waves – move the surface up and down

L waves – move the surface in all different directions, including circular motion

Older children may then want to research how scientists are designing earthquake resistant buildings.

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

Yeast – Examining Living Cells

Yeast - Examining Living Cells

Yeast . . . it turns grapes into wine . . . it makes bread rise . . . but did you know it’s actually a living one-celled fungus? Yeast provides a safe way for children to observe a few of the life processes of living cells.

1. Living Cells Need Water – Add dry yeast to very warm water to activate them. Explain to children that the yeast must have water in order to carry out life processes. They are able to survive in a dormant state without water, but they won’t become active and grow until they have water.

2. Living Cells Need Food – Put some of the hydrated yeast culture in two small containers (preferably clear). Add sugar to one of the containers, but not to the other. Let children observe the differences they see over time. Does “feeding” the yeast cells make them more active?

3. Living Cells Produce Waste – The yeast culture with sugar will give off noticeable amounts of carbon dioxide gas in the form of bubbles. Explain to children that the cells are getting rid of waste just like they do . . . by “breathing” out carbon dioxide gas.

4. Living Cells Reproduce – If a microscope is available make a slide from a drop of the yeast culture with sugar. Look carefully and you may find a cell that is undergoing “budding.” Budding is the way yeast cells reproduce. First they double all the material inside the cell that’s needed to keep it alive. Then they separate out one set of the material and pinch it off in a little pocket on the side of the cell. The new pocket will eventually pop off and form a new yeast cell! Children enjoy seeing the “baby” yeast cells. 🙂

Extension – Make bread or another pastry that requires yeast to make it rise. Ask children to use what they have learned about the yeast cells to explain what is happening inside the dough. (The yeast is eating the sugar and using the water in the dough to grow. As it grows it produces waste in the form of carbon dioxide gas. The gas bubbles are what makes the bread rise. As the yeast reproduces, more and more yeast cells can produce more and more gas bubbles and the dough gets bigger and bigger!)

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

Rotational Motion with a Pinwheel

Rotational Motion with a Pinwheel

Kids love to play with pinwheels. Whether you buy one at the store or make your own (pinwheel making tutorial), add a little Physics to the fun!

1. Use a string and ruler to measure the outside distance around the outside of the pinwheel.

2. Mark one spot on the pinwheel in some way. Use color, a piece of tape, etc. Just make sure the mark is very visible, even when the pinwheel is spinning.

3. Have your child practice watching the pinwheel in motion and counting each time the pinwheel makes a complete revolution. (When the mark on the pinwheel goes all the way around and returns to the same spot.) Move on to practicing counting exactly 10 revolutions. When your child has this down, move on to step 4.

4. Use a stop watch to measure the time it takes for the pinwheel to make 10 revolutions. Repeat 5 times, then average the 5 trials to get the “average time” for 10 revolutions.

5. Divide the average time by 10 to get the time for 1 revolution.

6. Calculate the speed at which the outside of the pinwheel was spinning by dividing the distance around the outside of the pinwheel (step 1) by the average time for 1 revolution (step 5). Your child has just calculated the rotational speed of the pinwheel!

To extend, repeat using different sources of “wind” to move the pinwheel at different speeds. Add a weather component by repeating on consecutive days to compare the wind strength. Older children may find it interesting to compare the actual wind speed (use a local weather app) to the speed of the pinwheel rotation. Look for patterns and mathematical relationships between the two.

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

How do colors affect temperature absorption?

How do colors affect temperature absorption?

We’ve all heard the fashion sayings . . . “never wear white after Labor Day” . . . “pastel colors should be worn at Easter” . . . etc. You know the traditions, but did you know they are actually based on science? The color of the clothing you wear can affect how hot or cold you feel when standing outside during the day.

The light reaching us from the Sun is known as “white light” and it is really made up of all the colors of the rainbow. Each of those light rays coming in contains energy. White materials reflect all colors away from their surface, absorbing none of the light energy. Similarly, light pastel colors reflect almost all the incoming light energy. Black materials absorb all light rays, allowing none to be reflected into our eyes. (That’s why it looks “black.”) Dark colors absorb almost all the incoming light energy.

So, you wear light colors in spring and summer to stay cool, and dark colors in the winter to stay warm. Fashion traditions are based on science! You can investigate this phenomenon with your children to prove that it works:

1. Select two t-shirts. Ideally, use one black and one white. If you don’t have black and white, use one that is as dark as possible, and one as light as possible. Also, select t-shirts that are similar in size and fabric type.

2. If possible, do the experiment outside on a warm, sunny day. Select a spot where you can lay the t-shirts out flat, side-by-side. Try not to set them on metal as this will affect the temperature.

3. If you have two similar thermometers, you can just insert a thermometer inside each t-shirt, wait for a select amount of time, and then read the thermometers. Try waiting about 15 minutes and then check for a temperature difference. Increase the time if necessary. Time will depend on the intensity of the sun that day.

4. If you only have one thermometer, try putting some water in two plastic baggies. Be sure to use the same type and size baggie, and the same amount of water. Place one of the baggies of water into each t-shirt at about the same place. Increase the time to about 30 minutes since it will take longer for the water temperature of the water to change noticeably. Be sure to check the temperature of the water in place. Bringing the water into the cool house can drop the temperature significantly while waiting to check the second bag.

To extend the experiment, especially for older children, repeat with different “medium” colors or prints to see what effect each has on temperature. You might also want to test how different types of fabric affect the absorption of light energy. Your children can then write their own “fashion rules” based on science!

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

Fingerprints

Fingerprints

A fun way to teach kids about their skin is through an activity on fingerprints. The skin has two layers: the dermis and the epidermis. The epidermis is the layer of dead cells on the outside of the body that waterproofs and protects the living tissues underneath. The dermis is the living skin layer that contains blood vessels, sensory receptors, and the dividing cells that create the epidermal layer. The upper part of the dermis has finger-like projections that stick up into the bottom of the epidermis. These projections, called papillae, allow the sensory receptors to be closer to the surface of the skin. In some areas of the body (palm side of hands and fingers, and bottom of feet and toes) the papillary layer is much thicker, causing it to bunch up between the epidermis and the lower dermis layers. This bunching causes the ridges and valleys we call fingerprints.

Contrary to what most people think, identical twins do not have identical fingerprints. Although genetics does determine the basic pattern, conditions in the womb influence how that pattern actually develops. Factors like rate of bone growth, pressure in the womb, and contact with amniotic fluid all affect the development of fingerprints of the fetus. Since it is virtually impossible for all those conditions to be exactly alike for 9 months, it’s safe to say that no two people have exactly the same fingerprints. The tiny details, called minutiae, that are used by forensic scientists to analyze fingerprints found at a crime scene are slightly different for everyone.

But, there are some basic fingerprint patterns and your child can easily recognize. Here are the basic fingerprint patterns:
fingerprint patternsLet your child make prints of his/her own fingerprints and identify the basic type. To make really detailed, long-lasting prints, use an ink pad. The ink will stay on the fingers for a few days, but most can be removed with rubbing alcohol and a good hand-washing. For a less permanent way to make prints, rub pencil “lead” heavily on one spot on a sheet of paper. Have your child press their finger firmly into the mark and then transfer over to clean paper to make a print.

Extensions of the basic fingerprint identification:

1. Fingerprint other members of the family and compare and contrast the prints. Do you find similar patterns? Different patterns?

2. For older children, use a magnifying glass to examine prints for tiny details (minutiae). Examine two fingerprints with the same basic pattern and see how many differences you can find. Examining prints at this level provides practice with observation skills and attention to details.

3. Set up a “who done it” activity for your child. Fingerprint several “suspects” and then make one “crime scene” fingerprint. Label all the prints with the suspects name or “crime scene.” Your child will have fun matching the crime scene print to one of the suspects! Adjust the difficulty level to the age of the child. For older children, choose a crime scene print that looks similar to the fingerprints of multiple suspects. Provide a magnifying glass so they can find a match by examining the minutiae of each print.

 

 

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
Page 1 of 3123