You Can Use an American Flag to Teach Math! {Giveaway}
Can a Human Circuit Light an LED bulb?
This past year when we were building lemon batteries, students had many of their own investigative questions. For one, students wondered if lemon juice would light an LED bulb. As a result, we tested lemon juice, apple juice, salt water, and many other liquids. Acting on their own questions fueled even more curiosity.
One student wondered if we could build a human circuit. I didn’t think it would be possible to light an LED bulb with a human circuit. I researched it on Google before I tried this activity with the students, and I found NOTHING about being able to light an LED with a human circuit. I had the students predict whether they thought that we could accomplish the lighting of an LED. Only about three out of ten students thought we could light the bulb.
Here is what we did:
- I had each student get one alligator clip wire to connect a pre-1982 penny and a zinc nail. (Doing this will give you about two more wires than you need, but at least everyone is busy.)
- I had about 10 students stand in a circle.
- Then each student in the circle held one pre-1982 penny in one hand between two fingers and with the other hand held one zinc nail between two fingers.
- Between each of the sets of students in the circle, I had the students hold the wire of an LED bulb. One student held one wire (positive) coming out of the bulb while another student held the other wire (negative).
- I made sure everyone was making a complete circuit for the electricity to pass through.
Then I heard the unthinkable. “I saw it light up!” one child exclaimed.
Now, I thought the students just saw a reflection, and it really wasn’t lighting up. Speaking to myself here—“Oh, ye of little faith.” Children are so optimistic, and I was blatantly reminded of my pessimism at this moment.
I turned off the lights because I wanted to be sure they weren’t imagining this. Sure enough, the electrical current flowed through all of the kids to create a human battery and light up an LED!!!
Side note: In case you aren’t having success with your human circuit. Make sure each child is actually making connection with a penny and a nail. There must be a penny, nail pattern in the circle. Flip the LED bulb the opposite direction if it doesn’t work the first time since each of the wires/prongs coming out of the LED are either positive or negative.
This could be an amazing team building experience with your students at the beginning of the year!
Cheap Mystery Experiments with Solids {Giveaway}
Originally I had planned for students to do the mystery liquids and mystery solids lessons together, but once students were doing their experiments, I realized we needed another class period to do the solids. This allows time for at least 15 minutes of rich discussion at the end. During the discussion time students tell what they think each solid is by defending it with their experiment data. 
Now, for each group of four students I made cups like the ones you see pictured. I collected seven substances that were white and powdery. Numbered cups help children determine which substance they are using and also help if they use the numbered plates I mentioned in the previous post. The substances can come from your kitchen cabinet or bathroom. These are the seven I used.
- Table salt
- Baking powder
- Baking soda
- Borax
- Powdered sugar
- Granulated sugar
- White Flour
Before allowing them to experiment, I asked them to discuss some of the ways that we could test these substances to see what they were. They mentioned the senses. At this point I tell them that we will absolutely NOT be tasting them, even though it would work in some cases, I let them know that these are NOT all edible. Further, I demonstrate how to use your hand to fan the scent of an item to smell it. Before I mentioned this, some students had sucked some of the substance up their nose by accident, and I didn’t want to repeat this problem. 🙂 Other ways to test that were mentioned were pH indicators, comparisons to other substances, and chemical reactions. Students had gathered significant data about these substances with pH indicators and chemical reactions in previous lessons.
Concerning materials management, I will be honest. I wasn’t brave enough to allow free access to substances for them to freely gather to do chemical tests. I dispensed these as needed.
All in all, the kids enjoyed being scientists, mixing substances to see the reactions, and creating new substances. This lesson needs at least an hour and maybe longer for students who take longer. Some of my classes took more than one class period, but most students needed just one.
Further, chemical reaction experiments are great to do before summer break because students will be inspired to do something besides sit in front of a screen during the summer. They might turn into real chemical engineers one day just by exploring their kitchen cabinets. (I always remind them to ask parental permission before exploring substances at home.) Now for a giveaway!
Mystery Liquids
If you have already allowed children to experience chemical reactions, they will be sure to enjoy figuring out which liquids these are. Now this experiment would go nicely with a CSI unit, if you tell children that these substances were found at a crime scene. Then tell them that they have to figure out which substances were left at the crime scene.
Now, for the practical matters of this experiment. First, I gathered five clear containers for each group and picked five mostly clear liquids. You can use whichever liquids you would like, but I chose
*water
*vinegar,
*very watered down dish soap,
*Sprite, and
*rubbing alcohol.
I colored every substance with food coloring except for the Sprite to make everything more mysterious. Also, just an FYI: I watered down the dish soap to the point where bubbles were almost undetectable, so it would be harder to figure out. I gave students small plastic spoons like the taste test spoons at an ice cream store to dip out the liquids. I also gave them wax paper because the surface tension of the water on wax paper is so evident compared to other liquids. Further, if they have a sheet of wax paper as opposed to a plate they waste less. Just have paper towels readily available.
Before I let the students have the materials, I made them tell what they could do to each substance to test it before they received the liquids. These are some of the things they told me.
- We can smell them.
- We can look at them.
- We can touch them.
- We can taste them. (at which point, I say absolutely not :))
- We can look at our old notes and test them with pH strips to see if the results match.
- We can do chemical reaction experiments.
- We can compare them to the substances that are available ( I had some liquids available).
During experimentation, I had several things available in extra supply for experimentation:
- extra solids available in small cups
- extra liquids available in small cups
- pH strips (I dispensed as needed)
- cabbage juice (I dispensed as needed)
(these were set up similar to the chemical reactions lesson I already shared)
I left time at the end of our class for the students to discuss which liquids they were and to support their conclusions. Most students were able to figure out all of the liquids except the water. Some students asked me if I had duplicated any of the liquids, and I did not. However, mwah ha ha, mwah ha ha (evil laughter), I did think about having two jars filled with water of different colors and having them figure this out.
Student Led Science with Chemical Reactions
As a precursor to chemical reactions, allow students some time to experiment with pH indicators, discuss the periodic table and chemical formulas, and take some time to do at least one teacher led chemical reaction such as a baking soda and vinegar explosion in a ziplock bag. Also, discuss the differences between a chemical and physical reaction.
Now this is how I allowed students to do their own chemical reactions…
*Students were able to choose what substances they wanted to mix.
*They were able to choose five reactions to perform.
*Students worked in groups of two. If they couldn’t settle on what to mix, I told them that they could choose two and their partner could choose two reactions. The last reaction they could do all alone.
*Students predicted what would happen in each reaction, and then recorded the results.
*I posed this question to the students before they began, “Will acids and bases always create a chemical reaction when mixed?”
Students were able to choose from the following substances to do their reactions:
- cream of tarter
- borax
- baking soda
- vinegar
- Sprite
- dishwashing liquid (watered down a bit)
- lemon juice
I used these little artist’s palettes with circular indentations in them for students to mix substances. These palettes were numbered so that substances could be numbered. I also had these little medicine cups that came with a science kit. The cups hold about one ounce. I had the different substances already poured out for students to use. Students could only get one cup of each substance, and if they were using the same substance for more than one experiment, they had to use that one cup for both experiments. The little spoons you see worked out very well. A colleague was getting rid of them, and I gladly took them off her hands.
This is further how I organized the materials at the supply table below. Again, this is not a beautiful blog picture, but it is real life after several classes had experienced this activity. I had different pieces of paper to organize the substances with the name on them. I told students they had to manage how to organize them at their own desk. In the picture above you can see that these students were very organized when they got to their table. They labeled their cups on notebook paper.
After students experimented many of them wanted to further mix what was already on their experimenting plate. I allowed this, but required them to write down what they had mixed.
In closing discussion, we talked about what happened when different students mixed different substances. We talked about whether these substances created chemical reactions, and students had to give evidence for a reaction being a chemical reaction. For example, did the substances produce gas, change temperature, or did they turn into completely different substances?
The students really enjoyed this learning experience, and this spurred them on to experiment at home on their own. I encouraged them to experiment over the summer especially because most of these substances can be found in the kitchen cabinet.
Use Chemical Reactions to Introduce Financial Literacy
Now, if you have already collected a bunch of pennies for the previous lemon battery experiment, you might as well do this experiment too. This experiment will make pennies look new, but you can make them extra dirty–or oxidized before you make them shiny. This experiment is quick and easy and has high impact.
First, to make your pennies oxidize or turn green, put your pennies in a shallow plate (see below) somewhere on a paper towel. Pour just enough white vinegar to let the pennies sit in the vinegar. You don’t want the vinegar to cover the pennies because you want the oxygen to reach them. You could turn the pennies over after they touch the vinegar so that both sides are able to touch the liquid. The combination of vinegar and oxygen will make them green. I have only done this when leaving the pennies for several hours or overnight, but the reaction will still happen with less time. The oxidation just won’t be as noticeable if done for an hour or two.
Note: I only used pre-1982 pennies which are mostly copper as opposed to new pennies which are filled with zinc and only coated in copper. This reaction I believe will still work with new pennies because the copper is on the outside.
Here is the end result below…they are all dried off. When doing this with children make sure you let them know that the pennies are not “rusting”, but that this is a chemical reaction between the oxygen and the vinegar called oxidation.
Now this is what I did in my lesson. I gave the kids an old green penny and a new penny (made 1982 and after). I told them to drop each penny on the table and listen to the difference in sound. Allow the kids to describe the differences in the pennies.
Next, I handed each child a small cup–in this case they are those little medicine cups. I had each child drop their old green penny in a cup and walked by to pour lemon juice just barely over the top of the penny. Then I had the children slide the cup from side to side to wash it in the lemon juice. I bought my lemon juice at Wal-Mart for about $2. If you have the leftover lemons from the lemon batteries, that juice will work too, but it is just easier to buy the lemon juice already made.
What is interesting is that the oxidation washes off in the cup and the lemon juice turns green. This is a great time to bring in the social studies aspect of the Statue of Liberty turning green from the oxidation.
I took this science experiment a step further and discussed inflation with the students by showing them a a video like this one about penny hoarders. We further discussed how the prices of goods and services are rising. Next, I give the students a chart and have them find the purchasing power of a dollar over time. We use this website to calculate the purchasing power of a dollar. They watch inflation from 1913 to the current year. This is very astonishing to them, and will organically lead to great discussion. Further, I give them a long term homework assignment and tell them that they are to pick one grocery store item and watch the price over time (this could take years). They are to see if the price of their item goes up or down and keep a record of this.
I hope you can enjoy using science to teach financial literacy in your classroom, too.
Scoop Up Your Wishlist Favorites at a Discount!
Scoop up your favorites on the Teachers Pay Teachers Sale! Every item in my store is 28% off for the Teacher Appreciation Sale. Here is your chance for you to gather those items on your wish list. Happy Teacher Appreciation to you all!
What You Haven’t Read about Lemon Batteries
Are you building a lemon battery? Here is how you build the battery, but I am going to tell you a few tips I learned through the process that I didn’t easily find on the internet.
(I apologize for not having pristine step by step photos of this process, but I am thinking about teaching when I’m taking these photos, so they don’t usually look perfect and bloggish. The potatoes are above also since we did potato batteries as well.)
1. Get about 3-4 lemons.
2. Roll the lemons on the table pressing a bit with the palm of your hand to get the lemon juicy.
3. Insert one copper penny into each lemon. The penny acts as the positive terminal. Push the pennies about halfway in.
*The penny should be made before 1982 (these were made with almost entirely copper). If they were made in 1982 or after they are only coated with copper. You may have to borrow a child’s piggy bank. I offered to pay my neighbor 5 cents for every penny she could find made before 1982. I decided to do this because when I got rolls of pennies from the bank, there were only about 2 or 3 made before 1982 in the whole roll. I was quite disappointed. I say don’t waste your time, and find someone with a piggy bank.
4. Insert one zinc nail (or screw) into each lemon. The nail acts as the negative terminal. Push it in with about 2 cm left outside of the lemon. Make sure the nail doesn’t touch the penny inside the lemon.
*The more contact the nail has with the lemon juice the better your lemon will work.
5. Buy some alligator clips to connect the penny in each lemon to the nail in the next lemon. You will need at least 5 wires for each set of four lemons you attach. Attach the wire on one penny and the the other end of wire on one nail successively. The wires on the lemons on the end need to be left unattached. These ends will attach to the lightbulb. This is my favorite go to image of the lemon battery. I leave this on the SMART board for the kids to see while putting together their batteries.
*You can order alligator clips from here and many other places. If you are in a pinch, you can go to Wal-mart’s automotive section and find red and black alligator clip wires there. (Lowes and Home Depot didn’t have the whole wire and clip put together).
6. Attach each end of the LED bulb to the lose alligator clips. Reference image link above in step 5. One end of an LED is positive and one end is negative, so students will have to switch sides of the bulb if their circuit isn’t working.
*To get LED bulbs cheaply, you can buy a $1 flashlight at War-Mart etc. and beat it with a hammer until you can break the bulbs out. This is a bit frustrating and took me about 30 minutes. You may also see if anyone you know including parents of your students have old LED Christmas lights they want to get rid of. When I put out a request for Christmas light strands, I got about 5-6 strands!!! Score!
*This is a great video if you are wanting students to understand how the electrons flow to make electricity work in batteries. If you are just wanting students to see the part about the battery, watch 1:34-3:55. If you want them to see how the lemon battery is built, you can continue watching until the end of the video.
What I definitely learned from experience:
*Yes, you can use the lemons for multiple classes. They will still work. I used the same lemons 3 back to back classes one day and four back to back classes the next. After a few days (I can’t remember exactly how many) the lemons will mold, and you won’t want to use them anyway.
*The nails will no longer work when they turn too black after a couple of classes. This is most often the reason the lemon battery doesn’t work for students who have all the wiring, pennies, and nails connected the right way. You will have to use new nails. They are relatively cheap, so no problem.
*The LED can burn out if you leave it connected too long. I tell the students to count to 20 seconds after they see it light up and then disconnect it. It will last longer than 20 seconds, but this is just what I tell them.
*You can use a 9-volt battery as a light bulb tester if you want to see if the LED works in case the kids insist that the light bulb is the problem. Touch each wire end of the LED lightbulb to the positive and negative terminals of the 9-volt battery. This will FOR SURE blow out the LED bulb if left for too long so just touch it barely to the 9-volt for half a second to see if it lights up. See here.
- Most often when the students’ lemon battery doesn’t work it is because:
- they have an alligator clip connected to two pennies or two nails. It is important that there is a penny, nail, penny, nail, penny, nail, penny, nail connection, or the electrons won’t flow from the negative to the positive.
- they have the LED light bulb turned the wrong way
- the zinc on their nails has corroded and the nails need to be replaced. This doesn’t happen with the pennies because lemon juice actually cleans pennies.
A great question to pose after this is, do you think you could light up an LED with fewer lemons?
The answer…Yes, you can sometimes light up the bulb with 3 lemons, but it will be dimmer. It is also possible to light it up with only one lemon if you can put enough pennies and nails into a single lemon. Now, I was never successful at this but, there are You Tube videos in which this has been explained.
5 Things to Know if Teaching Wiring with Electricity
While wading through teaching electricity, I learned a few hints that I wish I had known before setting out on this venture.
The following applies if you are teaching children to wire bulbs from Christmas light strands.
1. If you strip wire, strip it a little at a time (about 2-3 cm). This will prevent the small strands of copper from falling out from the friction.
2. After you strip the wire, twist the exposed copper ends a little at a time to prevent the small strands of copper wire from falling out. Then the copper wire will be stronger and easier to use.
3. If you allow students to use Christmas lights from the strand, it works best to just pull the bulb out completely and connect each end of the bulb wire (see small arrows above) to a Christmas light. At times, you can cut the wire with the bulbs still in the wire and they worked, but more often than not, it didn’t work to cut the wire with the bulbs still in them.
4. If you cut Christmas light wire to do wiring with Christmas lights, the thin wire will only carry about 12 volts before it overheats. I learned this from an electrician.
5. If you use LED bulbs, be aware that one end of the LED bulb will be a positive end and one end will be negative. This makes it more difficult to wire these type of bulbs. This is because you don’t know if the circuit has a bad connection or if the bulb is turned around the wrong way.
Here is one of the best classroom models the kids made below. They did one of the best wiring jobs!
