real science for today's homeschooler

Slinky Waves

Slinky Waves

Have an old slinky collecting dust in the kids’ toy box? Pull it out and teach a quick lesson on the two types of waves.

1. Loosely stretch the slinky across the floor or long table with you holding one end and your child holding the other.

2. Create a transverse wave by shaking one end of the slinky horizontally across the floor or table. Continue shaking back and forth to set up a series of transverse waves that will move from one side of the slinky to the other.

3. Have your child identify the crests and the troughs of the waves.

crest and trough

4. Also explain that in a transverse wave the energy moves perpendicular (at right angles) to the motion of the medium. They can see the medium (the slinky) move side to side while they feel the energy being transferred from your hand to theirs. Help them to see that the motion of slinky and energy are in different directions.

5. To make a longitudinal or compression wave, make a quick shoving motion with the slinky toward the person at the other end. You should be able to see a compression travel along the slinky between your hand and the person on the other end. Continue making compression waves in the slinky for your child to observe.

6. Have your child identify the compression and the rarefaction (see below).

compression and rarefaction

7. Explain that in a longitudinal or compression wave the energy moves in the same direction as the motion of the medium. In this case, they should see that both the slinky and the energy from your push are both traveling in a straight line between your hand and theirs.

If you are trying this with small children it may be difficult for them to identify the motion of the medium vs the energy. At lower grade levels, just focus on the fact that there are two different kinds of waves and how they look different. If your child is ready for new terms, help them identify the parts of one or both types of waves.

Finally, for all children, extend the lesson to brainstorm where they have observed (or how they can make) transverse and longitudinal waves in different types of media (water, rope, air, etc.)

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Growing Bacteria at Home

Growing Bacteria at Home

First, a warning . . . if you grow bacteria at home there is always a possibility you could grow large amounts of harmful bacteria that could make someone in your household sick. Always use proper safety precautions when growing bacteria! Some safety hints are included below, but always, always use common sense when handling any bacteria culture.

When bacteria cultures are grown in the lab the bacteria is grown in shallow containers (Petri dishes) on a layer of nutrient agar. These supplies can be expensive, but you can simulate this setup at home with substitute ingredients.

First, the containers . . . any shallow, disposable container will work. The smaller the container, the less base material you’ll need. Very important safety tip . . . the container should NEVER be closed up air tight! Some of the most harmful types of bacteria are anaerobic, meaning they grow when there is no oxygen present. Be sure your bacteria culture is always exposed to oxygen! Leave the lids of your containers loose.

Next, the nutrient agar. Agar is just a plant-based gelatin. You can buy it from science supply stores, or you can use a substitute. I’ve heard of people using plain gelatin powder from the grocery store, but animal-based gelatin melts at around room temperature. Also, some bacteria are able to produce a chemical that breaks down animal-based gelatin. So, I don’t recommend using plain gelatin powder like Knox, as you may come out with a watery mess!

Instead, look for “agar agar” which is a flake type gelatin made from seaweed. It’s used as a thickener in many Asian foods and it can usually be found in Asian grocery stores, or any large grocery that has an Asian foods section. You just dissolve the flakes in boiling water and then cool to room temperature to solidify.

Gelatin alone won’t serve as a food source to encourage bacteria growth, so you need to add some type of nutrient media to the agar agar when heating. I would suggest adding a beef bouillon cube. It adds a food source to your gelatin, and its high salt content will often suppress the growth of bacteria that is at home in the human body (and may cause illness). Again, this doesn’t mean you can’t grow a harmful bacteria, just that it helps lessen the possibility! Caution should still be used in handling the bacteria cultures!

A final note about safety . . . never, never allow someone to culture their throat or nose, or cough into a dish. A relatively “safe” source of microorganisms to culture for small children is soil bacteria and fungi. Dig up some dirt, add enough water to thoroughly soak the soil, and allow the mixture to soak for 10 minutes. Then pour a little of the water onto the growth medium and spread it around. Soil is full of harmless bacteria and fungi that will grow a very impressive culture in the container!

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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.

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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!

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Backyard Ecology

Backyard Ecology

No matter whether you live in the country or the city, your child can observe nature close to home. Help your child be a nature detective to discover the ecosystem existing right in their own backyard.

First, help your child identify what types of plants and animals they are realistically likely to see. If you have land in the country they’re likely to observe large mammals such as deer and racoons. If you have a tiny backyard in the city, help your child realize that they will be looking for small animals such as insects, lizards, birds, etc.

Depending on the age and interest of your child, prepare a plan to capture an image of the plants and animals they find. A digital camera works well, but if your child likes to draw they can turn the ecosystem hunt into an art project.

Over a span of a week or two, sit quietly outside with your child and observe nature. Have them find as many different plants and animals as possible. To find some of the more shy animals, help your child turn over rocks and other objects in the yard or on the porch. Try observing at different times of day, and even go outside with a flashlight at night to find animals that come out after dark.

For younger children you may just want to print out the photos and identify the different types of plants and animals found. They can make a collage or a notebook to display what’s living in their backyard. Older children may also want to research what each type of animal eats and design a food web based on that information. One method is to glue the images on a poster board. Then draw arrows going from the prey (or plant) to the predator. Older students can then examine their food web to infer other animals that might be a part of their backyard ecosystem that were never observed.

Whether you focus on the exploration or turn the project into an in depth ecology lesson, your child is sure to gain an appreciation for nature’s ability to sustain life anywhere!

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Outdoor Activity Explains Energy and Work

Outdoor Activity Explains Energy and Work

Energy is defined as the “ability to do work.” Energy and work are really different forms of the same thing, but to a child, they are very different. Try this simple outdoor summer activity to demonstrate the relationship between gravitational potential energy and work.

First, children need to understand gravitational potential energy. Explain to your child that a ball on the floor has no potential energy because it won’t move by itself. But, a ball on the edge of a shelf has potential energy because it can fall off of the shelf. While the ball is moving, it has energy. While the ball is sitting on the shelf it has “potential” energy because it has the “potential” to fall.

Children also need to know that the scientific definition of “work” is moving an object through a distance. The larger the object and the farther the object is moved, the more work is done on the object.

Next, explain to your child that energy is “the ability to do work.” Relate this to the ball sitting on the shelf. When the ball falls off the shelf and hits the ground, will it do work? (Technically, the answer is yes. The ball will transfer energy to the molecules in the floor, causing them to heat up slightly. But, this is not something that can be easily explained or understood by a child!) The following activity will help your child answer the question.

1. Place a pan of water on the sidewalk or driveway so water splashing out can be easily observed and/or measured.

2. Use a ball that has enough weight to make a splash when dropped into the pan of water. Raise the ball 1 foot above the surface of the water. Drop the ball into the water and observe.

3. Small children can observe how far the water splashes, or mark the farthest splash with sidewalk chalk. Older children should measure the distance from the edge of the pan to the farthest splash and record.

4. Fill the pan if needed. Repeat the ball drop from a height of 2 feet. Observe, mark, or record how far the water splashes from the pan.

5. Continue several more trials so that your child can observe that the higher the height of the ball, the farther the splash.

Now, relate the activity to the concepts of energy and work. When the ball is held above the water, the ball has potential energy. The higher the ball is held, the more potential energy it has. When the ball is dropped, the potential energy is released and the ball moves. (Technically, the potential energy is converted into kinetic energy, or the energy of motion. You may want to introduce this added concept with older children.) When the ball hits the water, the energy from the ball is transferred into the water, causing the water to splash out of the pan. Since the water is moved through a distance, the ball does work on the water. The more potential energy the ball started with, the more work it does on the water, and the farther the water can be moved.

To extend the activity and allow your child to use up some of their own potential energy, encourage them to experiment with “adding energy” to the ball by throwing it into the water to see how far they can get the water to splash!

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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!

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Understanding and Measuring Friction

Understanding and Measuring Friction

For elementary children, the topic of “opposing forces” can be hard to understand. Friction is an opposing force that children can “feel.” Here’s a lab on measuring and comparing friction that’s appropriate for older elementary children. You will need one piece of “science equipment” to get the most out of the lab . . . a spring scale. A spring scale with small increments will be easier for elementary children to use.

Here’s what to do:

1. Find an object that can be easily hooked onto the spring scale, that is fairly heavy (but will still read when hung from the spring scale), and preferably with a large, flat surface. A heavy block of wood with a cup hook works very well.

2. Have your child hook the object onto the spring scale and drag it across the smoothest possible surface you can find. While dragging the object slowly, have your child read and record the amount of force they are using to move the object. (Newtons is a measure of force, so the part of the scale marked as “N” is actually a measure of force.)

3. Next, have your child hunt for 5 different surface with as many different textures as possible. The surfaces must be large enough to drag the object across, just as was done in step 2.

4. Ask the child to predict what will happen when they drag the object across the different textured surfaces. They will most likely come to the conclusion that some surfaces will be harder to pull across than others. Ask them to come up with an explanation for WHY this is true.

5. Introduce the topic of “friction” by explaining that friction is a force that acts in the opposite direction from the force you apply to move an object. When they drag their object one way, the surface tries to pull it the opposite way!

6. Now, have your child predict which of their selected surfaces will pull more than others. Have them rang the surfaces in order from least friction to more friction.

7. Finally, it’s time to test their predictions. Have your child drag the object in the same way across each of the different surfaces. As they are slowly dragging the object, they should read and record the force they must use to pull the object.

8. Subtract the force needed to pull the object on the smooth surface from the force needed to pull it on each of the textured surfaces. This is a measure of how much more force the textured surface was putting on the object. The larger the number, the more friction force was applied by the surface.

To put it all together, remind your child that a force is just a push or a pull. So, when they put a force on the object in one direction, the surface will put a force on the object in the opposite direction. The more force applied by the surface, the harder they have to pull to get the object to move.

As an extension, relate this topic to the practical chore of moving a heavy object. Have them brainstorm ways that can be used to make sliding a heavy object easier.

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Learning about Earth’s Past through Creative Writing

Learning about Earth's Past through Creative Writing

Most kids love to be creative and make up stories. Use that creativity to research Earth’s past. Depending on the age of the child, you might want to first introduce them to the Geologic Time Scale. Here’s a good website with some basic information from Britannica Kids. For younger children, you might just help them pick a topic from Earth’s past, such as “dinosaurs.”

Next, help your student narrow down a specific time period (or topic) that sounds interesting to them. Help them research what the Earth was like during that time. Consider including the plants and animals that lived during that time, the climate, and what the land and oceans were like.

After your child has collected information appropriate for their age, challenge them to write a story about the time. Here are a few ideas to help get you started:

1. Write a first person story involving a time machine that takes them back to that time period for a week.

2. Write a story from the point of view of an animal that lived during that time.

3. Write a story about an alien who visits Earth during that time period.

If you give your child the freedom to make up their own creative story about their time period or topic, they are sure to have fun while learning quite a bit about Earth’s history!

 

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Calculate Speed While Encouraging Exercise

Calculate Speed While Encouraging Exercise

We all know that kids have a lot of energy. Put that energy to good use by combining a physics lesson, a math lesson, and some good exercise! All you’ll need is an energetic kid, a tape measure, a stopwatch, and a safe place for your child to run.

Calculating Speed

1. Pick out a “track” that your child can run safely. Select a distance appropriate for your child to run several times.

2. Help your child measure the distance of the selected track with the tape measure. You can measure with any units: yards, feet, meters, etc. Have your child record the track distance.

3. Measure the time it takes for your child to run the selected track. If possible, measure the time in seconds. Record.

4. Introduce the formula used to calculate speed:  speed = distance / time

Depending on the math level of your child, help them calculate their speed by dividing the distance of the track by the time it took to run it. Older children can calculate speed using long division. For younger children you may want to introduce the usefulness of technology by showing them how to get their answer with a calculator.

5. Repeat the run with the same track, or a different one as long as your child is interested and energetic. Challenge them to improve their speed with each run.

As an extension of the lab, students can compare their speeds when a) wearing different types of shoes, b) running on different surfaces, or c) running courses of different lengths. Any of these options will increase your child’s interest in the lab, as well as give them extra practice with division . . . and a little more exercise!

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