real science for today's homeschooler

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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What is my Ecological Footprint?

What is my Ecological Footprint?

Our children have a very egocentric view of life and, through limited life experience, they typically assume everyone has the same type of lifestyle as they do. While we talk a lot about conservation, how do we really measure up to other people? As you study ecology and conservation with your child, go online with them to take one of two Ecological Footprint Quizzes to reveal the size of your family’s ecological footprint. The first EFQ is very visual and fairly basic and simple and would be the best for younger children. The second EFQ is more in depth and would be great for older children.

The results that come up from the first quiz will reveal several interesting facts . . . and they may surprise you! How many acres of land are needed to sustain your lifestyle? How does that compare to the average person? If everyone had the same lifestyle as you, how many earths would we need to survive? The second quiz gives results about the number of earths needed to sustain you, and a breakdown of what areas of your lifestyle are consuming the most natural resources.

The first quiz is provided by an organization called “The Global Footprint Network” and the second by “The Center for Sustainable Ecology.” Besides the quizzes you can also find a good bit of information on conservation at either website. The quizzes are definitely eye-opening and can lead to some great discussions about protecting the environment and conservation of natural resources.

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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!

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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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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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