Energy changes (cognito) Flashcards
(25 cards)
What is an exothermic recation?
It is a reaction that releases eat to the surrounding, therefore the tempreture increases
how would exothemic rection profile look
the reactant would be above and the products below
name 3 examples of exothermic reaction
combustion, oxidation, neutralisation
what is an endothermic reaction
Take in energy from the surrounding, tempreture decreases
how would the energy profile look for endo
reactant low and products high
what is an activation energy
The minimum amount of enrgy particles need in order to collide with each other and react.
bond energy is
amount of energy required to break one mole of a particlar bond
breaking bond is an
endothermic reaction
making bond
is an exothermic reaction
to calculate if the reaction id exo or endo thermic you have to
energy reqired to break bond - energy releaased by forming bonds
if the answer to calculation negative then the reaction is
exothermic
How is an electrical cell made
A cell can be made by connecting two different electrodes with a wire, and placing them in contact with an electrolyte. An electrolyte is just a liquid through which charged ions can flow. There will often also be a voltmeter so that you can measure the voltage of the cell.
difference between cells and batteries
Batteries are very similar, but consist of two or more cells connected together in series to provide a greater voltage.
Factors that affect the voltage of a cell
- The metals used for the two electrodes. The greater the difference in reactivity of the two metals, the greater the voltage will be.
- The type and concentration of the electrolyte used.
- The conditions, such as temperature.
what are rechargable cells
Rechargeable cells and batteries can be recharged because the chemical reactions are reversed when an external electrical current is supplied. These are the batteries used in laptops and mobile phones.
what are non-rechargable cells
In non-rechargeable cells and batteries the chemical reactions stop when one of the reactants has been used up. These are the batteries usually used in smoke alarms and tv remotes. Alkaline batteries are non-rechargeable.
how does the ful cells work
as fuel enters the cell , it becomes oxidised and loses electrons.Thi sets a potential difference across the cell which drives the electrons around the circuit to generate the elctricity.
what are pros of hydrogen-oxygen fuel cell
it only reqiure hydrogen and oxygen which are both abundant, it does not produce any waste or CO2, it last longer than normal batteries
what are the cons of hydrogen-oxygen batteries
hydrogen is a gas so it will need more space to store than fossil fuels
hydrogen is explosive whan mixed with air
also to make the reaction happen you need energy which comes from fosil fuels
Fuel cells convert the chemical energy in a fuel and oxygen into:
Electricity
Which direction do the electrons flow in a hydrogen-oxygen fuel cell?
From the anode to the cathode
What is the overall reaction for a hydrogen oxygen fuel cell?
hydrogen + oxygen ➔ water
What is an electrolyte?
A solution through which ions can flow
how are the anode and cathode placed in fuel battery
In fuel cells the anode (which is drawn on the left) is negative, while the cathode (drawn on the right) is positive.
This is the opposite way around to the anode and cathode in electrolysis, so be careful not to mix them up.
