Exo and Endothermic Experiments

Disclaimer: I did NOT make up these experiments. I got them out of our Chemistry Level 1 book from Pandiapress.com. And I highly recommend them.


Plugging along with our year in chemistry we have come to chemical reactions. First we had to get through protons, neutrons, electrons, atoms, elements, molecules, and a few other fun little things, and now we’ve made it to the Bill Nye exploding stuff, right? Not quite. However, these experiments were so fun. I was kind of skeptical that I could get them to work right. I would never have made a good scientist probably of any kind, I’m not a good baker for the same reason – something to do with measuring things? But after a little trial and error, we nailed these guys!

Our exothermic reaction occurred when we added yeast to vinegar. The kids stirred it up, oooo’d and aaaahhhh’d at the bubbles, and then felt the temperature start to rise in their cups. This was so fun that we had to do it twice!

Our endothermic reaction was a little harder to pull off. The first time we did it nobody could feel much of a temperature change. But the kids really liked the bubbling so for fun I just kept adding more baking soda to the lemon juice to see if we could keep the bubbles going. And what do you know? Our little cups gold colder and colder the more baking soda I added and the more they stirred and stirred. You know, I know it is science and explainable and all, but sometimes it feels kind of like magic! Just because you know what is going on and why, doesn’t it seem magical when you can create a change like that. All those little molecules rearranging themselves and stuff, it’s just kind of neat.

My greatest success of these experiments was not that they worked, but that, thanks to our study of latin prepositions, I finally wrapped my head around the phenomena of endo- and exothermic reactions. Exothermic makes sense – heat right? One of their products is heat. But endothermic was explained to me in IB Chemistry in high school as a chemical reaction that used the surrounding heat as a catalyst to make the reaction happen, therefore the reactants, or the new products I guess, would be cold. To a high school mind using heat to make something cold was hard to swallow. Thankfully somehow it has clicked. Exo – heat exiting equals warm/hot to the touch. Endo – heat going in equals the absence of the heat and therefore cold to the touch. Easy peasy.

Here is proof that even if you ran out of ink in your printer and couldn’t print off the worksheets to go with the experiments AND even if you had you couldn’t totally complete them anyway because your cheap-o thermometer from Walmart broke after only a few days and now you are without, your kids can still have fun doing science. (And even though they don’t actually answer my question in the video, they did answer all my verbal questions correctly during the science lesson. It’s just kind of hard to compete with bubbling concoctions at your fingertips!)