Today, I was browsing pinterest for a fun project and came upon this fun chemistry activity called the Penny Battery. This particular activity is from Khan Academy (if you haven't heard of them, they offer lots of free online instruction in many different areas). The way it works, you look at the activity guide to determine what materials you need and the basics, then you watch videos showing you how to do it and what it means. I was very happy to find that we had everything we needed at home and it could be gathered in just a few minutes. That may not be the case for your home if you don't have family members who are into electronics.
For this activity, we collected 5 pennies (4 that were newer than 1982), a piece of cardboard cut into 4 small squares, water, salt, vinegar, sand paper, electrical tape and an LED.
We followed the instructions by sanding one side of the 4 post-1982 pennies so that the zinc core was completely exposed on one side. This allowed us to access the zinc on one side and the copper on the other side of each of the 4 pennies. The pre-1982 penny does not have a zinc core so it was only copper. The sanding took the most time, about 5 mins per penny (T did 3 of them while I was collecting the other materials).
Then we added salt to the water to make a saturated solution. To this we added a splash of vinegar to make it acidic. Then we soaked the cardboard squares while we finished sanding.
Once everything was ready, we stacked the pennies and the salt water soaked cardboard to make the battery. Each sanded penny was placed with zinc (silver color) facing up, then a soaked square was placed on top of it. Next, we placed one set on top of the other ending in the copper only penny. Each cell is made of zinc, salt water cardboard and copper in that order and there are 4 cells in this battery.
T was very excited about his LED lighting up and after we wrapped it with electrical tape, he proceeded to walk around the house using it as a flashlight in dark rooms.
The Khan Academy also has a video explaining how this reaction works. It was clear enough for my nearly 8 year old to understand. I drew a small diagram while I was explaining it to him. Please ignore my horrible handwriting, I am a scientist and we aren't known for our handwriting.
There is also a challenge in this activity to determine how to alter the battery to make a blue LED light up. A blue LED requires more voltage so that means more pennies. T quickly said that you would need 7 pennies, and then we watched the video. He was right, seven pennies lit up the blue LED. We didn't have a blue LED to test it out with but seeing it the video was good enough for him to cheer that he knew he was right LOL.
There is just something about Science that will peek interest and keep things going when we are just running out of steam. Thanks Khan Academy! (I am in no way affiliated with Khan Academy, I just really enjoyed using this site and thought Id pass it on. Also, you don't have to sign up for anything to use the site, it only asks you to create an account if you want to track your progress)