C5 Chemical Cells and Fuel Cells

C5 Chemical Cells and Batteries

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Learning Outcomes

- Recall the definition of an exothermic reaction and it’s uses

- Describe the difference between a battery powered electric

vehicle and a hydrogen fuel cell vehicle

- Give the advantages and disadvantages of a hydrogen fuel cell

vehicle.

What do you know already?

Multiple Choice

If a chemical reaction is EXOTHERMIC, the temperature would....

• Stay the same

• Increase

• Decrease

Multiple Choice

What type of reaction occurs in a hand warmer?

• exothermic

• endothermic

Multiple Choice

What type of reaction is this?

• Exothermic

• Endothermic

• Kinetic

• Potential

Multiple Choice

$$6\ CO_2+\ 6\ H_2O\ +\ Energy\ \rightarrow\ C_6H_{12}O_6\ +\ 6\ O_2$$

• endothermic reaction

• exothermic reaction

Multiple Choice

If they energy required to break the bonds is less than the energy given out by making new bonds the reaction is

• Exothermic

• Endothermic

• Neutralisation

Energy Changes

Recap Q.

What are the definitions for:

Endothermic reaction:

Exothermic reaction:

Transfers heat energy to surroundings, surrounding temperature increases.

Absorbs heat energy from surroundings, surrounding temperature decreases.

Supplies electrical energy.
The larger terminal (on the left) is positive (+).

Supplies electrical energy.
A battery is more than one cell joined
together.
The larger terminal (on the left) is positive (+).

CELL

BATTERY

Cells and Batteries- What is the difference?

Alkaline vs Rechargeable Batteries

In non-rechargeable batteries the chemical
reactions stop when one of the reactants
has been used up.

Alkaline batteries are non-rechargeable.

In rechargeable batteries the chemical
reactions are reversed using an external
electric current.

Chemical Cells
To make a chemical cell;
Electrode: A conductive material e.g. a
metal rod.

Electrolyte: A conductive liquid that
often decomposes over time causing
the cell to run out of charge.

To increase the voltage in a chemical
cell we increase the difference in
reactivity of the two metals

Multiple Choice

What is a battery?

• A single cell

• Two or more cells connected in series

• AA or AAA

• An alkaline substance

Multiple Choice

What type of reaction takes place in a chemical cell

• Exothermic

• Endothermic

• No reaction occurs

Multiple Choice

In non-rechargeable cells, why do the chemical reactions stop over time?

• One of the reactants becomes used up.

• The energy has depleted.

• The products are oxidised.

• The electrodes become reactive.

Multiple Choice

What are the main components of a chemical cell?

• An anode, a cathode

• An anode, a cathode and an electrolyte

• An anode and an electrolyte

• A cathode and an electrolyte

Multiple Choice

What is an electrolyte?

• An electric current

• The splitting of ionic compounds

• A solution containing ions which allows current to flow.

• The salts in drinking water.

Multiple Choice

What does the potential difference of a cell depend on?

• The anode and cathode.

• The type of electrolyte and fuel

• Whether it's alkali or not

• The type of electrode and the electrolyte.

The future of cars…

Why do you think we might need to consider the future
fuel for cars and other vehicles?

Hydrogen Fuel Cells

Fuel cells work by using the reaction
between hydrogen and oxygen to
produce an electric current:

This is an exothermic reaction.

hydrogen + oxygen → water
2H2 + O2 → 2H2O

activation
energy, Ea

energy given
out during
reaction

Energy

Progress of reaction

2H2 + O2

2H2O

Multiple Choice

What is a fuel cell?

• A cell which uses hydrogen to generate electricity.

• A cell which uses oxygen (or air) to generate electricity.

• A cell which uses a fuel to generate electricity.

• A cell which uses a fuel and oxygen (or air) to generate electricity.

Multiple Choice

Fuel cells produce

• Fossil Fuels

• Hydrogen gas

• Electricity

• Gasoline

Multiple Choice

In a hydrogen fuel cell used to power a car, where does the oxygen come from?

• The air

• A catalyst

• The fuel

Multiple Choice

What is the main reason why hydrogen is more difficult to store than diesel?

• Hydrogen is a gas at room temperature but diesel is a liquid

• Hydrogen can be liquefied by cooling it

• Hydrogen can be stored under pressure

Multiple Choice

What is produced by a hydrogen-oxygen fuel cell?

• Water and Carbon Dioxide

• Carbon Dioxide

• Water

Multiple Choice

State three disadvantages of hydrogen fuel cells

• Do not need to be recharged, no pollutants are produced, can be different sizes for different uses

• Hydrogen is highly flammable, hydrogen is sometimes produced through non-renewable means, hydrogen is difficult to store

Multiple Choice

Complete the equation which occurs at the positive electrode of a hydrogen fuel cell O₂ + 2H₂O →

• OH⁻

• 2OH⁻

• 3OH⁻

• 4OH⁻

Multiple Choice

Complete the equation which occurs at the negative electrode of a hydrogen fuel cell 2H₂ + 4OH⁻ →

• H₂O + 4e⁻

• 4H₂O + e⁻

• 4H₂O + 4e⁻

• 3H₂O + 2e⁻