Monday, December 6, 2010

Peanut Brittle Math - Volume verses Weight

We're getting ready to make peanut brittle tonight, but first I thought we'd do a quick Math Monday lesson, with the peanuts.

I showed the kids, that the recipe called for a pound of raw peanuts. Usually we buy our peanuts in bulk, but this year all the store had was prepackaged peanuts. So, I already knew each package was exactly one pound, but I didn't point that out to the children.

Instead, I asked them how many ounces are in a cup - 8 ounces.

And, how many ounces are in a pound - 16 ounces.

And, if 2 cups of peanuts would make a pound? They were pretty sure it was a trick question. Apparently, they had learned something about volume and weight from our snow experiment. They suspected they weren't interchangeable, but they weren't sure why.

So, we placed our old, clear, measuring cup on our scale, and zeroed the scale out (a lesson in itself).


The girls measured out two cups of peanuts, with our smaller one cup measure, pouring them into the bowl on the scale.


Two cups did not equal one pound.


In fact, it took three cups of peanuts to make a pound.


Finally, we talked about the difference between volume, and weight - how a fluid ounce, is not the same thing as an ounce used for weighing, and how it all becomes clearer by turning the measuring cup around to the metric side, where volume is measured in liters, and weight is measured in grams.

You can find more fun with math at this week's Math Monday link-up, over at Joyful Learner.

It's great to be a homeschooler.

6 comments:

Phyllis said...

Great lesson! Many adults don't know the difference between volume vs. weight. We did a chemistry leson with peanut brittle, too.
http://homeschooljournal-bergblog.blogspot.com/2010/09/physical-vs-chemical-change.html

Raising a Happy Child said...

That's a pretty advanced lesson for the younger ones. I admit that it bugs me that US cannot switch to metric system that the rest of the world uses. I find it extremely confusing and even now translate everything back to metrics (except baking when I got used to cups and TSPs)

Wonder Mom said...

I love that your kiddos are making connections between the snow experiment and the peanut experiment...

Ticia said...

That always amuses me, and I have to admit there's some things I"m lazy on for measuring where I know it's different and I haven't bothered to fix it.

Christy said...

I'm impressed. I love that you find lessons in everything you do.

Joyful Learner said...

I'm impressed too. It is not an easy concept to master. Like Natalie, I too wish we would switch to metrics. Would make life so much easier.