Chemistry Energy Changes Sept 2018 Flashcards
What is an exothermic reaction?
A reaction in which thermal energy is transferred from the chemicals to the surroundings and so the temperature increases
What is an endothermic reaction?
A reaction in which thermal energy is transferred from the surroundings to the chemicals and so the temperature decreases
What is an application of an exothermic reaction?
Hand warmers and instant heat packs use exothermic reactions to heat up quickly
What is an application of an endothermic reaction?
Instant cold packs use endothermic reactions to cool down quickly
What is activation energy?
The minimum amount of energy that particles need to react.
In exothermic reactions is the energy of the product higher or lower than the reactants? (Remember the graphs)
Lower
In endothermic reactions is the energy of the product higher or lower than the reactants? (Remember the graphs)
Higher
What is required to break bonds?
Energy
What two things occur in a chemical reaction? (In terms of bonds)
- energy must be supplied to break bonds between
reactants. - energy will be released when bonds are made
between the products.
What is the overall energy change?
The difference between energy to break the bonds in the reactants & the energy made when bonds are made between products
What is the equation for energy change?
energy needed to break bonds in the reactants - energy released when bonds are made by the products
What is a cell?
Two electrodes in an electrolyte used to generate electricity
What is a battery?
Two or more cells connected in series
What is an electrolyte?
A liquid that contains electricity
What two factors affect the voltage of cells?
The metals: The identity matters. The greater the difference in reactivity, the greater the voltage.
The electrolyte: Changing the electrolyte and/or the concentration can affect the voltage
