Energy Changes Flashcards
What is a exothermic reaction?
A reaction where energy is transferred to the surroundings so surrounding temperature increase (combustion, oxidation and reduction) - energy released from forming bonds is greater than that needed to break the bonds
What is an endothermic reaction?
Where energy is taken from the surroundings so surrounding temperature decreases (thermal decomposition) - energy needed to break bonds is greater than energy released making them
What is activation energy?
Minimum amount of energy particles need to react
What happens in a chemical reaction in terms of bond energies?
Energy is supplied to break bonds and energy is released when bonds are made.
How do you find the total energy of reaction?
Energy of reaction = sum of bonds broken – sum of bonds made
What is a cell?
A cell is composed of two electrodes dipped in an electrolyte solution. It produces electricity from a chemical reaction.
What is a battery?
A battery consists of two or more cells connected in series.
What is a rechargeable cell?
Chemical reactions are reversed when an external current is supplied
What is a non-rechargeable cell?
Reactants are used up, cannot be recharged
What is a fuel cell?
Fuel cells are supplied by fuel and oxygen to oxidise the fuel to generate electricity.
What are the advantages and disadvantages of hydrogen fuel cells?
Advantages: no pollutants, no recharging
Disadvantages: flammable, H2 difficult to store, fossil fuel production, toxic chemicals, expensive production of H2 by electrolysis