Energy Changes Flashcards
Cells
Cells contain 2 different electrodes in contact with an electrolyte
Electrodes are able to conduct electricity, and the electrolyte contains ions which reacts with the electrodes
How do metals react with electrolyte
Different metals react DIFFERENT with SAME ELECTROLYTE which causes a different VOLTAGE within the cell
The type of electrode used will affect the voltage of the cell, and the LARGER THE DIFFERENCE IN REACTIVITY
If the metals are the same, the voltage produced will be 0
How can a simple cell be made
Connecting two different metal electrodes with an electrolyte in contact
Batteries
Consist of 2 or more cells connected in series
Non rechargeable cells
Chemical reactions stop when one of the reactants has been used up, eg. Alkaline batteries
Rechargeable cells
Can be recharged because the reversible reaction is utilised when an electric current is supplied
How do fuel cells work
- fuel supplied (HYDROGEN) and oxygen
- hydrogen is oxidised within cell
- producing a potential difference
- releases energy
- electricity ting
- WATER IS PRODUCED
Hydrogen fuel cell advantages and disadvantages
- don’t give off harmful pollutants
- good supply of energy
- flammable
- expensive
Cells and batteries advantages and disadvantages
- cheaper
- some rechargeable
- convenient source of energy
- harmful chemicals
What is the conservation of energy?
The amount of energy at the end of s chemical reaction is the same at the beginning of the reaction
Exothermic reactiom
One that transfers energy to the surroundings so the temperature of the surroundings increases
Endothermic reaction
One that takes energy in from surroundings so the temperature of the surroundings decreases
Exothermic reaction examples
- respiration
- combustion
Endothermic reactions examples
- photosynthesis
- thermal decomposition
Activation energy
The minimum energy required for the reaction to occur
Reaction profile
Graph the energy changes in a system during a reaction
How are bonds broken
Energy is supplied to break the bonds
How is energy released in a reaction
When bonds are formed
Exothermic reaction (bonds)
Energy released from the making of bonds is greater than the energy required to break existing bonds
Endothermic reaction (bonds)
Energy required to break existing bonds is greater than the energy released when bonds are made
