Science Saturday Challenge #1

Welcome to Science Saturday Challenge #1!

We'll start with something you have probably seen before: making a pH indicator.

Materials:

Red cabbage (1 head)
White vinegar (1/2 cup)
Baking soda (1 tsp)
Water
Eye dropper
Clear glass containers (at least 3)

Procedure:
Shred the cabbage. Put it in a medium pot and add water until the cabbage is covered. Bring to a boil and then let it cook for about 15 minutes. Really, I just watch it on the stove until the water turns a dark purple. Strain the mixture so you only have the liquid. Do whatever you'd like with the cabbage.

I got almost a quart of indicator from one small head of cabbage. That will keep in the fridge for awhile (my jar has been sitting there for several months.)

While the liquid is cooling, get out three glass containers (or more if you are testing more than baking soda and vinegar.) In each put:

1/2 c water + 1 tsp baking soda (stir to combine)
1/2 c water
1/2 c vinegar

In my pictures, I actually used a cup of water but the color will be more intense if you use less.

Once the indicator has cooled a bit, add 15 drops of it to each of the three containers.

The acid turns pink, the base turns blue, and the water will stay purple (red + blue = purple, acid + base = neutral liquid)

Why? Because cabbage and many other plants contain anthocyanins that change color depending on pH. These substances are what show through in colorful autumn leaves when the chlorophyll drains away. They are also why some plants will have different colors when planted in different soils.

Links for more information:

What are acids, basis, and pH? See if your acids and bases have these properties. Instead of vinegar, I actually added ascorbic acid to water. Ascorbic acid can be purchased through The Baker's Catalogue as a dough enhancer and to make sourdough bread more sour! What about slippery soap--any guesses as to its pH?

How Stuff Works: Where does the color come from in purple cabbage?

Acids and Bases: Frequently Asked Questions (advanced)

Water to Wine: the molecular basis of indicator color changes (advanced. If the chief stewart tasted these liquids, though, he would not comment to the groom that he had saved the best wine for last!)

Introducing Science Saturday

I am starting a new project here called Science Saturday. On Saturday I will post a science experiment for you to try out during the week.

Blog about your experience and leave a comment on the Science Saturday blog entry for that experiment. Include a link to your blog entry for others to see.

I hope this will encourage homeschoolers to explore more science and have a lot of fun!

Making butter part II

We ran out of the first batch of butter we made, so I bought more cream and made some more. This time, however, I did it right.

I shook the jar until it all solidified, just like before, only this time I shook a little more. It only took a few more firm shakes, enough to move a semi-solid mass of cream, when suddenly it filled with liquid again--buttermilk!

The butter was now yellow (our last batch was white) and had the consistency of butter. It even harden in the refrigerator, which the last batch did not. And ds#3, who didn't care for the last batch, loves this one (he has discerning taste.)

I replaced the stick butter in my decorative butter dish instead of keeping it in the jar. I estimate that I got a pound out of the quart of cream, plus about a 12 oz of buttermilk.

Skin model

We finished our first model, skin, from The Body Book. I ripped the pages out of the binder, put each in sheet protectors, and scanned what I need, and printed it out onto heavy paper. The subcutaneous (bottom) sheet is actually card stock while the other two are 28# paper. It is all held together with tape and was easy to assemble.

Each layer flips up on tape hinges. The boys enjoyed putting this together; we refer to it while reading through Blood and Guts.

We also demonstration the effectiveness of evaporation by rubbing a little isopropyl alcohol, which evaporated quickly, on one hand and water on the other. The alcohol feels much cooler.

One experiment not in the book that I want to try with the boys demonstrates that cold and wet are both sensed by the same sensors. Blindfold your subject and put something cold, but dry, on them and ask if they feel something wet...

Snowflake pictures

It is snowing again today--big, light flakes. Inspired by In the Sparrow's Nest, I went out and took some pictures of these snowflakes. When you really take the time to observe them, like while trying to photograph them, you realize just how big they are.

The detail is amazing. You can clearly see in these photos that each has six sides and is unique. As you can see, the flakes show up best on a dark background, and you should let it get cold enough so that the flakes don't melt when they land on it. (Given that our temperatures are somewhere in the high 20's right now, it didn't take too long.)

You don't have to be as close as these photos appear; these are cropped, so at an arm's length you still get great detail.

Check out information on Wilson A. Bentley, The Snowflake Man, for more about these marvelous creations. (Thanks, Melissa!)