real science for today's homeschooler

Measuring Volume

Measuring Volume

Many science activities rely on taking an accurate measurement of the volume of liquids and solids. Below you’ll find a reference for how to measure the volume of different types of matter. Activities in this blog that require students to measure volume will include a link back to this page for reference.

VOLUME OF A LIQUID

This one is easy . . . add the liquid to a container that measures volume! 🙂 One suggestion would be to find measuring containers that measure in milliliters (mL)and (L) so that children become familiar with metric measurements.

VOLUME OF A REGULAR SOLID

A “regular” solid means one that has a specific geometric shape whose dimensions can be measured accurately with a ruler. Here are some of the basic formulas used to measure the volume of geometric shapes:

formulasBe sure to measure lengths in metric units such as centimeters (cm) or millimeters (mm). All volume measurements will then be in cubic centimeters  or cubic millimeters.

VOLUME OF AN IRREGULAR SOLID

The water displacement method is typically used to measure the volume of an “irregular solid,” a solid that lacks a regular geometric shape whose dimensions can be measured with a ruler. To use the water displacement method you will need a container that will hold the object to be measured, and that is marked in metric units, preferably milliliters.

1. Fill the container with enough water to cover the object.

2. Record the amount of water in the container, preferably in milliliters.

3. Insert the object to be measured, being careful not to let it “plop” in and splash water out!

4. Record the new water level in the container.

5. Subtract the two water levels to determine the amount of water that was “displaced” (moved out of the way) when the solid object was inserted.

6. Because 1 milliliter of water = 1 cubic centimeter of water, you can assume that the volume of water displaced in milliliters is the same as the volume of the solid object in cubic centimeters.

Many of the activities in this blog will require that students find the volume of different substances. This page will be linked so you can easily return for a refresher on measuring volume! 🙂

 

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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.

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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!

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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.

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Water Conservation

Water Conservation

How many times do you have to remind your kids . . . “Turn off the water!” . . . or, “Turn off the light when you leave the room!” Kids are forgetful and they sometimes need help developing good conservation habits. Here’s a simple activity that will make your kids aware of how much water they can waste simply by brushing their teeth!

1. Find a large bowl that will just fit into the sink to collect water running from the faucet.

2. Have your child brush their teeth as they typically do, leaving the water running the entire time.

3. When they finish brushing and rinsing, measure the volume of the water collected in the bowl. You can use any measurement that works for the tools you have on hand. Cups might be the best, as you can convert your final measurements into gallons. Students have a good concept of how much a gallon is when they think about a gallon of milk.

4. Repeat the process, but this time, have your child turn off the water when they are not using it to wet the toothbrush, rinse, etc. When finished, measure the amount of water used.

5. Have your child subtract the difference between the amount of water used when running the faucet the entire time and when only turning it on when necessary. Convert to gallons: 1 gallon = 16 cups.

6. Finally, have your child calculate the number of times they brush their teeth in one year. Multiply by the amount of water that can be saved at each brushing. The amount of water wasted each year by letting the faucet run is surprising!

7. To extend for older children . . . multiply that amount of water by the number of people in your household to see how much water the family could save in one year. Then, help your child read a recent water bill to determine how much your utility company charges per gallon of water. Use that figure to calculate the amount of money your family could save by turning off the faucet while brushing your teeth!

Disclaimer: If you follow this project through to the very end, be ready for your child to transform into the “faucet police”! 🙂 Once children “see” the results of conservation techniques they do tend to become aware of what everyone around them is doing!

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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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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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Popsicle Science – Turn a Summer Snack into a Science Lesson!

Popsicle Science - Turn a Summer Snack into a Science Lesson!

Do you make popsicles for your kids during the summer? Involve them in the process and turn it into a science lesson!

Materials:

juice, plastic cup, ruler, waterproof marker, popsicle stick (or plastic spoon), index card

Procedure:

1. Fill a small plastic cup about ½ full of juice. (Cups with the straightest sides work best.)

2. Cut a slit in the middle of an index card and place it over the cup. Insert a Popsicle stick or plastic spoon through the card and into the liquid, holding it upright with the index card.

3. Make a mark on the outside of the plastic cup at the top of the juice.

4. Measure the height from the bottom of the cup to the mark. Record.

5. Place the cup in the freezer and leave undisturbed until frozen.

6. Remove from the freezer and measure the height of the frozen juice. Record.

7. If age appropriate, calculate the change in height and record.

8. Ask the question, “Why is there more juice in the cup when it is frozen?”

How it works:

Juice contains a large amount of water. Water is one of the only substances on earth that expands when it freezes. Most liquids contract as they get colder as the molecules slow down and get closer together. Water does contract as it cools all the way down to 4°C. But between 4°C and 0°C (the freezing point of water), the water molecules actually begin to spread farther and farther apart. Solid water (ice) is less dense than liquid water because the molecules in ice are spread farther apart than in water. That’s why ice floats in water.

 

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