energy changes Flashcards
describe what an exothermic reaction is and give an example
they are reactions that transfer energy from the reacting molecules to the surroundings and causes the surroundings to get hotter. Examples of exothermic reactions include burning, some oxidation reactions and neutralization
describe what an exothermic reaction is and give an example
they are reactions that transfer energy from the reacting molecules to the surroundings and causes the surroundings to get hotter. Examples of exothermic reactions include burning, some oxidation reactions and neutralization
what is an energy profile diagram
it is a diagram that shows the amount of energy during a reaction as time passes. If the energy of the products is less then the reaction is exothermic and if it is more then it is endothermic
what is an endothermic reaction
it is a reaction where energy is taken in from the surroundings causing the surroundings to get colder
what is activation energy
it is the minimum amount of energy that particles need to react
what is the practical for temperature changes
measuring a set amount of hydrochloric acid in a polystyrene cup in a beaker to stop it falling over. add a small volume of sodium hydroxide and add a lid to the cup with a hole for the thermometer and stir the thermometer and record the temperature change
how do we make a cell
we make a cell when two different metals are put into an electrolyte
what is the difference between a rechargeable and a non rechargeable battery
in a non rechargeable battery the reactants run out. However a rechargeable battery uses a reversible reaction so does not lose its reactants
is the equation at the positive end of a fuel cells electrode
2H₂ –> 4H+ + 4e-
what is the equation at the negative end of a fuel cells electrode
O₂ + 4H+ 4e- –> 2H₂O
what are the advantages of hydrogen fuel cells as compared to rechargeable batteries
Hydrogen fuel cells wont run out as long as there is a constant flow of hydrogen whereas rechargeable batteries run out
hydrogen batteries do not become less efficient over time unlike chargeable batteries
Hydrogen fuel cells provide drinking water
what are the disadvantages of hydrogen fuel cells
hydrogen is an explosive gas that is hard to store and have a relatively low potential difference so multiple are needed
