A Theme Week: Valentine's Day

I'm going to try my hand at a theme week...

Next week is Valentine's Day, a rather minor holiday in the grand scheme of things, but it tends to involve hearts, lots of hearts.

Just for fun, each day this week I'm going to share a science activity related to the heart (and by extension, the cardiovascular system).  I hope you'll find something you can use in this week leading up to Valentine's Day or next Monday, on the big day itself.  Many of the activities are very simple and require little set-up.

So, without further delay, here comes the first heart activity....
(And I promise to return to typing in black - I was momentarily overcome with Valentine's spirit).