exothermic and endothermic reactions Flashcards
what happens in endothermic reactions
energy is taken in from the surroundings so the temperature of the surroundings decrease
examples of endothermic reactions
sports injury packs, electrolysis, thermal decomposition, reaction between citric acid and sodium hydrogencarbonate
what happens in exothermic reactions
energy is released into the surroundings so the temperature of the surroundings increase
examples of exothermic reactions
hand warmers, combustion, oxidation, and neutralisation
what do you sue to measure changes in heat
thermometer
do neutralisation reactions give out or take in energy
give out
does displacement reactions give out or take in energy
can do either
do combustion reactions give out or take in energy
take in
materials used for the required practical
dilute hydrochloric acid, dilute sodium hydroxide solution, styrofoam (polystyrene), calorimeter & lid,
25 cm3 measuring cylinder
Thermometer & stirrer
method for practical (steps 1-3)
using a measuring cylinder, place 25 cm3 of the NaOH solution into the calorimeter, measure and record the temperature of the solution, add 5 cm3 of the dilute HCl and stir
method for practical (steps 4-5)
measure and record the highest temperature reached by the mixture,
repeat steps 1 – 4 increasing the amount of acid added by 5 cm3 each time
define activation energy
minimum amount of energy required for a reaction to take place between reacting particles
describe what an exothermic reaction profile would look like
the energy of the products will be lower than the energy of the reactants, so the change in energy is negative
describe what an endothermic reaction profile would look like
the energy of the products will be higher than the energy of the reactants, so the change in energy is positive
energy change equation
energy taken in (used to break bonds) - energy given out (released from forming bonds)
