Energy changes

Created by

Emily Hurt-Reyes

Cards (66)

What is a chemical cell?
Using chemical reactions to transfer energy by electricity
Why are some cells non-rechargeable?
The reaction will stop when one of the reactants is used up
What is a rechargeable cell? 
When an electrical current is supplied, and the reaction will reverse
How can you provide a higher voltage? 
The greater the difference in reactivity between metal electrodes, the greater the potential difference/voltage that's produced
Which electrode will oxidise?
The least reactive one.
What happens during oxidation?
What is oxidation?
The gain of oxygen, The loss of electrons
What happens after anode is oxidised?
Reduction occurs
Where does reduction occur? 
At the cathode
What is reduction?
The loss of oxygen, The gain of electrons
What happens to the ions produced at the anode?
They are transferred into the electrolyte solution
What happens to the mass at the anode?
It decreases
What is a redox reaction?
Where reduction and oxidation occur
What happens after the two redox reactions?
A potential difference is created, produces voltage
What is an electrolyte?
The solution of water or other solvents
What happens to the mass at the cathode?
It increases
Why does the mass increase at cathode?
The gain of electrons
Advantages of chemical cells
Advantages of non-rechargeable cells  
Cheap
Reliable
Advantages of rechargeable cells
Reusable
Long term cost effective
Measure of power usage
Uses less resources
Disadvantages of non-rechargeable cells
Non-reusable
Waste packaging
Chemicals are toxic
No measurement of power used
Environmental impacts
Disadvantages of rechargeable cells
Expensive manufacture
Chemicals are toxic when disposing
Constant recharging
What are some uses of rechargeable cells?
Laptop
Phones
What are uses of non-rechargeable cells?
Mechanical watches
Remote controls
What is a fuel cell?
They contain a fuel, an electrolyte and oxygen
What is the common fuel used?
Hydrogen
What are common uses of fuel cells?
Hydrogen powered cars and trains
What is the overall reaction of a hydrogen fuel cell?
$2H2 +$ $O2 → 2H2O$
What are the two types of reactions?
An acidic electrolyte
An alkaline electrolyte
What happens first?
The fuel enters (usually hydrogen)
What happens to the hydrogen?
It's oxidised in the anode, with electrolyte
Whats the 1/2 equation at anode in acidic electrolyte?
$2H → 2H +$ $2e-$
What happens to the electrons in anode?
They flow through the circuit and into the cathode
what happens to the newly formed H+ ions?
The travel through the electrolyte into the cathode
What happens at the cathode in acidic cells? 
Oxygen enters the cell and is reduced, with the H+ ions
What is the reduction equation? 
$02+$ $4H +$ $4e- → 2H20$
Why are fuel cells good?
The only product is water, which is not toxic
What happens to hydrogen at anode in alkaline electrolyte cell?
Still oxidised, but with hydroxide ions
What's the equation for oxidation of H2 in alkaline cell?
$H2 +$ $OH- → 4H20 +$ $4e-$
What happens at the cathode in alkaline cells?
Oxygen enters and is reduced with the H20 from electrolyte