Cells and batteries

Ready to race?

• You have 1 minute to write down as many different appliances/gadgets that use batteries.• GO!!

Guess what?

• Very few of those items we just wrote down actually use batteries!

• The word ‘battery’ is used when in actuality, you’re referring to a ‘cell’.

• A cell is a device that uses chemical reactions to produce a flow of electrons

• A battery is more than one cell connected• However the words battery and cell are

interchangable

The next task….

• Let’s write down some of the devices that you identified that use batteries• I’m going to draw a square around

one type of device and a circle around another type• Can you figure out the pattern?

Don’t say it out loud! I’ll ask later…

Electric Cells are usually made by separating 2 DIFFERENT metals and putting a liquid that can

conduct electricity between them.

Ever made one of these before?

Why a lemon?• Lemons contain acid; acids

conduct electricity well

Electrons will flow from one metal to the other.

Moving electrons ARE electricity, so as electrons pass through the liquid to move from 1 metal to the other, electricity is flowing.

For instance, Au+3 ions want electrons more than Al atoms, so if you mix Au+3 and Al, electrons will move from Al to Au+3.

Al Au+3

These moving electronshave energy which we can “steal” from them and use to power our iPods, torches and electric cars.

So in every battery, you force electrons to move and you steal energy from them as they move.

Most batteries consist of two metals (the metals are called ELECTRODES) connected by a solution (called an ELECTROLYTE) that conducts electricity.

As electrons move from one metal to the other, the metal that is losing electrons breaks apart.

Eventually, all of the metal is gone. That is when your battery is dead.

Watch!

• http://www.chem.iastate.edu/group/Greenbowe/sections/projectfolder/flashfiles/electroChem/voltaicCell10.html

Electrons flow FROM the aluminum to the copper.

As they pass through the light bulb, it steals some of their energy.

As the aluminum loses electrons, it breaks apart, and gets smaller and smaller.

Eventually, there won’t be any aluminum left and the battery will be dead.

There are 2 main types of cells: dry cells and wet cells.

• A dry cell contains 2 metals but its electrolyte is a paste, rather than a liquid.

A wet cell battery also contains 2 metals, and its electrolyte is a liquid.

Usually wet cell batteries use sulfuric acid as the electrolyte.

Companies like to use sulfuric acid because it’s cheap (more profit!) and easy to buy (less work!)

But sulfuric acid is also very dangerous, so you have to be very careful when using batteries. If you spill some sulfuric acid on yourself, it will burn through your skin quickly, all the way to the bone!

• So, what’s the pattern that you see on the board??

Some batteries can be recharged and some cannot.

Our textbook calls rechargeable batteries “secondary cells” and non-rechargeable batteries “primary cells”

If you are using laptop when it is not plugged in, lithium atoms in the computer’s battery turn into lithium ions, and they release energy.

Then, as soon as the laptop is plugged in, the computer uses energy –electricity from the outlet-- to turn the lithium ions back into lithium atoms.

Disposing of Batteries

Use the internet to research how you should dispose of batteries (dispose of means “throw out”).

Fuel cells

As you know, almost every car company in the world is now making electric cars and hybrid cars (A hybrid car uses both electricity and petrol to power the car. The Toyota Prius is a hybrid car).

Electric cars and hybrid cars use fuel cells.

A fuel cell is a box where an energy-producing reaction takes place.

In wet and dry cells, the chemicals that produce the electricity are stored inside of the cell.

In a fuel cell, the chemicals that produce the electricity are stored outside of the cell.

HOMEWORK

Read page 437 to 444Answer question 2 on page 443Answer questions 2-4 on page 445