The lesson is a basic overview of how batteries and fuel cells work. It's important because rather than using unfamiliar experimental materials it uses things like salt, soda cans, charcoal and cloth, which students will be very familiar with.

The lesson should be taught after some circuits lesson (e.g. flashlight), or to students with basic knowledge of circuits. There should be some front-of-class review of previous circuit material, then a discussion of what is actually going on inside the battery. The concept of charges should be explained, preferably with magnet props. After this students will work in pairs to build salt-water batteries which they can measure with voltmeters. After this, there should be a brief class explanation of series and parallel circuits, then the students should go into larger groups to connect the batteries to light an LED (this could be a competition). If there is time and willingness to insert a design component, the students could be given a challenge to design the most effective salt water battery (to concepts like maximizing surface area etc).

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@@Science/Technology principles@@

Not applicable

If design section is done: creating a variation on a design by optimizing given criteria (i.e. improving SW batteries)

Teamwork - students will need to experiment in teams.

Students build their own sets of salt-water batteries.

PEN lessons that meet the requirement are noted in brackets.

basic circuits (flashlight lesson)

Not applicable

any electronics lesson

Magnet demonstration: to demonstrate positive and negative charges. Teacher should have multiple magnets and a fairly smooth surface, so that they can demonstrate how the magnets can either repel each other (demonstrating similar charge) or attract each other (demonstrating opposite charge)

Students build salt-water batteries in pairs. They are each given a can, a small section of cloth and two wires. Charcoal, water, salt and wire strippers are passed around. The students will first be shown a brief front-of-class explanation, then teaching assistants should go around helping individual students.

Then after an explanation about series/parallel, the pairs of students gather in groups of around 4 or 5 pairs and are given LEDs to light by connecting their batteries.

Optional design work could be done after the bulk of the lesson. Explain the factors that make a battery successful (greater surface area, stirring electrolyte etc) and have students make designs that improve on the standard salt-water battery.

- One aluminum soda can per 2 students. Cans should be pre-sanded (on the inside) and their tops cut off. If it is too difficult to sand on the inside, sand on the outside and ADD one plastic carton per can.

- Salt (take a whole 500g-ish salt canister, just in case!)

- Charcoal (enough for an eyeball-sized lump in each battery can)

- Thin-gauge electrical wire, cut into pieces about 6 long, 2 per pair of students, plus some extra. - Water! Enough to fill all the cans - Small pieces of cloth (roughly 2 x 2''), one per pair of students plus extras.

- Elastic bands, at least one per pair of students.

- small LEDs, at least one per pair of students. These can be found in many cheap flashlights.

- Set of two or more magnets for charge demonstration

- Chalkboard or whiteboard with moveable magnetic dots, or circular paper cut-outs + blutack for charge board demo.

- If LEDs have been taken from a flashlight/other device, show where they were taken from!

- Scissors (as many as possible, so can be passed around)

- Wire strippers (ditto)

Ideal class - 20-40 students, paired up. One main teacher, 2 or more teaching assistants to go around the class and help with experiments.

Why should students want to participate in this lesson?

They get to make electricity and do a cool experiment using materials they know about - so they can get a chance to try it themselves at home very easily.

Why should teachers want to teach it?

Get to teach science that is not usually taught, but about things that will be instantly recognizable to students.

Competition element (“salt water battery races”) is a lot of fun.

Figuring out an anode-cathode metaphor on the fly is good teaching experience! (I've taught this a few times a different metaphor worked each time)

If this lesson (and its prerequisites) were the only PEN lessons someone took, what should they be able to do?

Describe how a battery actually produces electricity.

Make a battery themselves out of an anode, a cathode and an electrolyte.

Describe a circuit as being continuous and made of moving charges.

If you had to teach this lesson tomorrow morning, what would you spend tonight working on? (assuming that materials were not an issue)

Different cathod-anode metaphors! This is a tricky one but usually you can find something that will click for a particular student (problem is, different things might work for each student…). Previous successful metaphors range from cooking yams to the plot of Mean Girls.

If you hadn’t taught this lesson before, what questions would you have for someone who had taught a very similar lesson?

How would you successfully work in a design element?

If the only materials available were broken radios, TVs, and computers, could you do all the electronics in this lesson? (assuming you had solder, soldering irons, etc.) If not, what would be missing?

YES.

If the only structural materials available were dish-cloths, cardboard, and plastic bags, could you make the mechanical bits of this lesson? (assume equipment as above) If not, what would be missing?

Not applicable.

Thanks for reading!