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The Happy Scientist: Lessons in Electricity

The Science of Making Butter

by Robert Krampf

My Grandmother is going to have her 103rd birthday this month. I have been thinking about how much the world has changed during her life. Imagine only having fruits and vegetables when they were in season. Imagine no computers, no television, no air conditioning, no refrigerators. This time we are going to step back in time a bit, and make our own butter.

To try this delicious treat, you will need

  • a small container of heavy whipping cream
  • a glass jar with a tight fitting lid

If you have never made butter, these instructions may sound strange, but trust me, it works wonderfully. The first thing to do is to let the cream sit on the counter, at room temperature, for about 12 hours. I put it out on the counter after supper, and I had freshly made butter on my toast the next morning.

After letting the cream sit, pour it into the glass jar. Don’t worry if it has a slightly sour smell. Put the lid on the jar. Now we have to shake the jar, but we don’t want to just start shaking it wildly. We want to watch what is happening. Give it one good hard shake about once every second. Watch carefully. For the first few minutes, not much will happen. Then suddenly, you will feel something solid hit the jar when you shake it. Look inside and you will see a large lump of butter. Give it a few more hard jolts and your butter should be ready.

Open the jar and look carefully. Around the butter is a thin, white liquid, which is commonly known as buttermilk. If you have ever had buttermilk biscuits, this is what they are made with. Pour off the buttermilk and add some cold water to the jar. Swirl it around a bit and then pour it off. Repeat this a few times, until the water remains clear. Drain all the water and put the lump of butter into a small bowl.

At this point, you have sweet cream butter, which is wonderful on hot bread or fresh biscuits. If you prefer salted butter, simply sprinkle some salt into the butter and stir it in. At this point, treat the butter just as you would the butter you get from the store.

That was quite yummy, but how and why did it work? First, we have to know a bit about milk. If you have ever been lucky enough to have milk fresh from the cow, you know that if you let it sit for a while, the cream floats to the top. That is because milk contains lots of tiny globules of milk fat, each surrounded by a thin membrane. Imagine tiny balloons filled with butter instead of air. Because the milk fat (butter) is lighter than the liquid, they tend to float. The cream that rises to the top is really a very high concentration of these fat globules floating on the milk. The milk from the grocery does not do this because it has been homogenized, a process that makes the fat globules small enough to keep them mixed evenly in the milk.

We left the cream out of the refrigerator overnight for two reasons. First, it helps the fat in the globules to form crystals. These crystals will help to break the membrane when we shake the cream. Imagine a water balloon with shards of glass inside. One jolt would cause the glass to slice through the balloon. That is what we want to happen.

Letting the cream sit at room temperature does something else. It allows lactic acid bacteria to grow. We think of bacteria as a bad thing, but many of them are quite useful. These bacteria make the cream more acidic, which prevents the growth of harmful bacteria. They also produce chemicals that give the butter a stronger and richer flavor.

When you shake the cream, some of the globules slam into the glass and break open. Soon, the cream is filled with tiny globs of butter. As these tiny bits of butter bump into each other, they stick together. The lumps of butter get larger and larger, as more and more globules are ripped open. Very quickly, you have one large lump of butter and a small amount of liquid buttermilk. I was amazed at how little liquid was left once the butter formed.

You will probably notice that the color of your butter is more pale that the stuff you buy at the store. Some manufacturers add yellow color, but a lot depends on what the cows are eating. Cows that eat grass get lots of a chemical called carotene, which adds a yellow color to the butter.

Of course, the true test of your butter is a fresh, hot biscuit, or some crusty French bread, or some nice pancakes, or some…. well, you get the idea.

Reprinted with permission. © 2008. Robert Krampf’s Science Education

Video: The Science of Feathers

The Science of Flame Color

Hunting for Rainbows and Sun Dogs

by Robert Krampf

This time we are going to learn how to look for rainbows. For many people, seeing a rainbow is a matter of chance, but if you know the science behind it, you will know when and where to look for them. To see that, we will make a rainbow of our own

For this experiment, you will need:

  • a sunny day
  • a garden hose

Be sure that it is a bright, sunny day, if you want to see a rainbow. You want the sun to be low in the sky, so it is best to do this in the morning or evening, not at noon. Turn on the garden hose. If you have a spray attachment, set it for the finest spray. If you don’t have a spray attachment, put your thumb over the end of the hose to make a spray. Look at the water drops. Do you see a rainbow? Probably not. Notice where the sun is. Watch the water drops as you turn slowly towards the sun. Once you are facing the sun, look carefully at the water drops. See a rainbow? No. Not yet. OK, now keep turning. As you slowly turn, continue to watch the spray. Ahh, there’s the rainbow. Once you see it, notice where the sun is. It is behind you!

In order for you to see a rainbow, the sunlight must enter the raindrop, pass through it, and hit the far side. It then reflects back through the water drop to your eye. In passing through the drop, the light is broken up into colors, just as if it had passed through a prism.

The best time to see a rainbow is when the sun is low in the sky and it is raining in the opposite direction. If it is morning, then the rain should be to the west of you, as the sun is rising in the east. In the evening, the rain should be to the east of you. Once you know where and when to look for them, rainbows are easy to see, but that does not make them any less beautiful.

Reprinted with permission. © 2008. Robert Krampf’s Science Education

The Science of Blowing Milk Bubbles

Milk Bubbles
by Robert Krampf

This week’s experiment explores a popular childhood activity, blowing bubbles in your milk. It is a great way to learn about surface tension, milk chemistry, and have fun doing things that your Mother told you not to.

To try this, you will need:

  • a glass of milk that is half full (or half empty, depending on your personal outlook)
  • a glass of water that is half full
  • a soda straw

The start is easy. Put the straw in the glass of milk. If the glass is more than half full, use the straw to drink the excess. Then blow gently through the straw, making bubbles in the milk. Continue doing this until you fill the glass with bubbles, or until your mother tells you to stop playing with your food and get ready for school. (Oops. Sorry. Childhood flashback.)

It was pretty easy to fill the glass with milk bubbles. Next, try the same thing with the glass of water. This is not nearly as easy. The bubbles pop very quickly, making it difficult to fill the glass with bubbles without blowing so hard that you make a mess.

Why the difference? Water molecules are very sticky, attracting each other very strongly. At the boundary between water and air, they make up for the lack of attraction above the surface by pulling even stronger to the sides. This forms a skin-like surface tension on the water. That surface tension is what pulls water into beads on a freshly washed car.

A bubble is made up of a thin film of water. With pure water, the pull of the surface tension make the water film so thin that it pops almost instantly. For the bubble to last longer, you need some way to reduce the surface tension.

Milk contains proteins. These proteins are long, string-like molecules that form a network in the bubble reducing its surface tension. Less surface tension lets the bubbles last longer, making it easier to fill the glass.

The amount of milk fat can also have a big impact on this. Liquid milk fat forms films in the bubble more easily than the milk protein, but since the fat does not mix with water, it does not reduce the surface tension. That makes weaker bubbles, so low fat milk tends to make better bubbles than whole milk.

Temperature also has an impact. With a glass of cold milk, the bubbles were large and lasted quite a while. As the milk warmed up to room temperature, the bubbles were smaller and popped quickly. This means that you should blow your milk bubbles early in the meal, instead of waiting to have bubbles with your desert

Reprinted with permission. © 2008. Robert Krampf’s Science Education

Watching vs. Spotting Nature

Nature Watching
by Robert Krampf

I have been an avid bird watcher for many years. When I first got started, I spent most of my time bird spotting, trying to add more and more species to my life list. While it is fun to add a new species, there is much more to bird watching than just spotting them.

To see what the bird spotters are missing, you will need:

  • birdseed

OK, so you need to find a place to watch birds. Luckily that is pretty easy, because you can find birds just about everywhere. They live in cities, forests and deserts. You can find them in the Arctic and in the middle of the ocean. You can even find them in your back yard.

Now you could easily go out in the yard and sit there waiting for a bird to fly by, but we want the birds to stay for a while. If you have lots of plants, they will probably do just that, but you can encourage them by putting out some food. Don’t put out bread crumbs or crackers. They are not good for birds. Instead, put out some sunflower seeds, millet, or unsalted peanuts. Place the food where you will be able to see it from your window, and where the birds will be safe from neighborhood cats and other predators.

Then wait and watch. Depending on the area, it may take a few minutes or a few hours for birds to find the food, and feel comfortable enough to stop for a snack. If you continue putting out food, within a few days you should have some regular visitors.

Once the birds are feeding, watch them. You will find that some species tend to be very aggressive, trying to chase other birds away from the food. Other species tend to ignore the other birds, gladly sharing the feast. Notice that different birds prefer different kinds of food. Watch the way different birds eat. Some will grab seeds and fly away to eat or hide them, while others will sit and nibble until they are full. Some will be very flighty, zipping away at any movement, while others will tend to ignore you as long as you don’t get too close. Notice how their behavior and sounds change if a cat comes into the yard.

The more you watch them, the more you will learn about how they behave. You can practice your skill at observation by watching other animals too. If you have a flower garden, watch to see if different types of bees and butterflies like different colors and types of flowers. Watch ants as they search for food. Is there a pattern to the way that they search? If they find food, do they follow the same path back to their home?

Observation is an important skill in science, and the better you are at noticing details, the more you will learn about science and the world around you. For example, earlier today I observed that there was still some ice cream left in the freezer. As a good scientist, I really should check on it again, to be sure that it is still there. Read the rest of this entry »

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