real science for today's homeschooler

Dinosaur Tracks

Dinosaur Tracks

Scientists often have to use indirect evidence to infer information about extinct species. Children (and adults!) often find it hard to understand how a footprint can tell a scientist anything about the animal that made it. Use this “mystery solving” activity to help explain how information can be collected from indirect evidence.

You will need to do a little advance preparation for this activity. You’ll need some play dough or other soft modeling clay and some plastic dinosaurs. Dinosaur models of different sizes and different types of dinosaurs will work best.

  1. Roll out the modeling clay in a flat sheet. This represents an area of soft mud like you would find along a river bank.
  2. Use the plastic dinosaurs to make footprints in the clay as if the dinosaur were walking through the mud. Be sure to space the footprints out to represent the natural stride length of the plastic figure. Also, adjust the depth of the footprint to represent the relative size of the dinosaur. A larger dinosaur would weigh more and so would sink farther into the mud, etc.
  3. Adjust the complexity of the footprint pattern based on the age of your child. Keep the pattern simple for younger children with only a few different dinosaurs with tracks spread apart. For older children, add more dinosaurs and have one track cross over another, etc.
  4. Allow the clay to dry completely. Don’t let your child see the clay or the dinosaur figures until you’re ready to have them do the activity.

The activity:

  1. First, give your child only the clay model. Explain to your child that this was once soft “mud” that dinosaurs walked through. Over time, the mud dried up and turned to “rock.” The footprints are indirect evidence that a dinosaur walked through a long time ago. If your child is old enough you can introduce the term, trace fossil. A trace fossil is anything that shows a prehistoric organism was there, but it doesn’t show what the organism actually looked like.
  2. Ask your child to look at the field and identify how many different dinosaurs walked through the field. For older children, have them trace the path of each different dinosaur, explaining what happened when paths crossed, etc.
  3. Now, have your child look at each different track present. Ask them to tell as much as they can about each dinosaur based on their footprints. Allow your child time to develop ideas on their own. Here are some things to suggest if they get stuck:
    • Ask children to compare foot size between members of their own family. Lead them to recognize that larger people have bigger feet and apply that to the dinosaur tracks. Have your child put the dinosaurs in order based on relative size.
    • Did each dinosaur walk on two legs or four legs?
    • Discuss “stride length” as it relates to height. Your child has probably noticed that they have to take more steps to keep up with dad! Explain that taller people usually have longer strides. Have your child relate this idea to the dinosaur tracks. Can they tell which dinosaur was taller and shorter based on stride length?
    • Have them measure the depth of the track. Relate this to the weight (size) of the dinosaur, since heavier objects would sink farther into the wet mud.
    • Finally, if any of your dinosaur figures had distinctive features on the feet, see if students can identify these from the footprints. (This all depends on the models you use. For example, some models may be detailed enough to show individual toes, claws, etc.)
  4. After your child has inferred all they can from the footprints, bring out the models that were used to make the prints. Have your child match up the dinosaur to their footprint. Compare all the figures used and evaluate how accurate your child’s predictions were to the real thing.

To extend the lesson, do an internet search to see of there are any dinosaur tracks close enough for a local field trip or a stop along your next vacation route!

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

Teaching Kids about Consumerism and Conservation

Teaching Kids about Consumerism and Conservation

Let’s face it, the advertising world targets your kids every day. What child hasn’t been disappointed after saving for months for a toy, only to find it doesn’t measure up to what the commercial promised? In my science classes I teach my students how science can be used to objectively test claims made by advertisers . . . in other words, how to be wise consumers. Here’s a fun idea that actually came from one of my students. It combines a lesson about consumerism, along with a lesson about conservation.

Design an experiment to test which is more cost efficient, using disposable or rechargeable batteries. I’ll list some of the variables to consider below, but your child can easily design this experiment themselves for some hands on practice using the scientific method.

1. Pick comparable battery brands to test. If you pick a name brand disposable battery, don’t compare it to a cheap store brand rechargeable, etc.
2. Use the same size battery of each type.
3. Test the battery life in the same way. An example would be using the battery to run any small electronic device. Measure the time the device remains in operation. Use the same device for both types of batteries, and keep the device under the same conditions (temperature, volume, etc.)
4. Decide on exactly what you’re comparing. Are you comparing the amount of time each battery will keep the device running? If so, you may want to also test different brands of each type. Are you trying to determine which type (disposable vs rechargeable) battery costs less in the long run? In that case, you’ll need to also factor in how many times the rechargeable can be recharged vs how many disposable batteries would have to be purchased to get the same result.

Again, those are just some suggestions of things to consider when designing the experiment. Your child will have plenty of ideas of their own. Gently guide them into using the scientific method to design their experiment so their results are valid.

Extensions of this lab are limitless! Older students can research the amount of waste produced by batteries or the amount of nonrenewable resources are used in the manufacturing of batteries. Find battery commercials or ads for the different brands and types tested. Challenge students to evaluate the claims made by the manufacturers based on the results of their experiment. This will usually lead to a discussion about the accuracy of claims made about other products. Encourage your child to select several products that are commonly used in your home and put them to the test! Teaching kids not to believe everything they see and hear from the media, and teaching them that they have the power to evaluate these claims for themselves is a valuable life lesson!

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

Seed Germination Lab

Seed Germination Lab

Children are fascinated by the fact that a seed can grow into a plant. You’ve probably already planted seeds with your child in order to watch them grow into plants. Here’s a slightly different way to show your child the actual process of germination that allows them to actually see the plant emerge from the seed.

Materials: seeds, paper towel, plastic sandwich bag, magnifying glass

Procedure:

1. Fold a paper towel so that it fits flat inside a plastic sandwich bag.

2. Soak the paper towel thoroughly with water. You want the towel very wet from end to end, but not dripping with excess water. Place the paper towel in the bag and lay flat.

3. Place seeds on the paper towel so that they are spaced out away from each other. Press each firmly into the wet paper towel. (Hint: Although any type of seed will work, small, fast-germinating seeds work best. Whole birdseed such as millet works very well.)

4. Seal the baggie to conserve water and place the bag in a place where it will be undisturbed.

5. Gently slide the paper towel out of the baggie each day and observe the seeds with a magnifying glass. Depending on the type of seed used, you should start to see the seeds germinate within a few days to a week.

6. Between daily viewings be sure to gently replace the paper towel into the baggie and reseal. Re-wet the paper towel if it begins to dry out. You should be able to germinate the plants long enough to see the first leaves develop.

Lab Variations:

  • When the seedlings begin to produce leaves, transfer to soil and continue to grow into a larger plant.
  • Prepare more than one baggie with the same type of seed. Place the baggies in different environments (temperature, sunlight, etc.) to see how environmental factors affect seed germination.
  • Prepare more than one baggie with the same type of seed. Put differing amounts of water into each baggie to see how different amounts of available water affect seed germination.
  • Prepare more than one baggie using a different type of seed in each. Compare germination times of different types of seeds.
Share this on...Email this to someoneTweet about this on TwitterShare on Facebook

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.)

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

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!

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

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!

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

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!

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

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.

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

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!

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
Page 2 of 3123