energy changes Flashcards
what is the conservation of energy principle
energy is conserved in chemical reactions. The amount of energy in the universe at the end of a chemical reaction is the same as before the reaction takes place.
what is an exothermic reaction
give examples
a reaction where energy is transferred to the surroundings so that the surrounding temperature increases
.combustion
.oxidation reactions
.nuetralisation reactions.negative sign of energy change
what is an endothermic reaction
give examples
a reaction where energy is taken in from the surroundings so the surroundings temperature decreases
.thermal decomposition
.reaction of critic acid and sodium hydrogencarbonate
.positive sings of energy change
what is activation energy
minimum amount of energy that particles need to react
what is a cell
a cell is composed of two electrodes dipped in a electrolyte solution. it produces electricity from a chemical reaction
what is a reaction profile
a graph which shows the relative energies of reactants and product, as well as activation energy of reaction
what is a battery
a battery consists of two or more cells connected in a series
what determines the voltage obtained from a cell
indentifies of metals used as electrodes and the identity and concentration of an electrolyte
state the advantages and disadisadvantages of using cells and batteries
advantages-
. more or less cheap
.some are rechargeable
.source of electrical energy
disadvantages-
.harmful chemicals
describe rechargeable and non-rechargeable cells
. rechargeable- chemical reactions are reserved when an external current is supplied
.non-rechargeable- reactants are used up , cannot be recharged
what are the advanatages 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
