Heat energy changes Flashcards
two types of energy change that can happen during a reaction
exothermic and endothermic
exothermic reactions
heat energy is given out
reaction mixture or surroundings increases in temperature
endothermic reactions
heat energy is taken in
reaction mixture or surroundings decreases in temperature
Exothermic or endothermic:
a) neutralisation
b) displacement
c) precipitation
d) dissolving
a) exothermic or endothermic
b) exothermic
c) exothermic or endothermic (depending on precipitate or salt)
d) exothermic or endothermic
Describe the apparatus you can use to measure temperature change
- beaker supporting a polystyrene cup
- cup contains reaction mixture
- lid with hole
- thermometer measuring temperature of reaction mixture
(the beaker and air act as insulators to decrease energy transfer)
What happens to bonds and energy when a chemical reaction happens?
- bonds that hold the atoms together in the molecules of the reactants are broken
- atoms come together in new arrangements to form the products
Why does an exothermic reaction release heat?
more heat energy is released making bonds in the products than is needed to break the bonds in the reactants
Describe the change in the energy levels of reactants and products in an exothermic reaction
energy is released to the surroundings from the products
the reactants start with more energy than the products have as it is released
Are breaking/making bonds exo or endothermic
breaking bonds is endothermic
(energy is needed)
making bonds is exothermic
(energy is released)
Describe the change in the energy levels of reactants and products in an endothermic reaction
energy is taken into the reaction
the reactants start with less energy and the products gain more as it is taken in
Why does an endothermic reaction take in heat?
less heat energy is released making bonds in products than is needed to break bonds in the reactants
Calcium chloride is added to water and stirred.
Explain why the mixture warms up.
exothermic change happens
more heat energy is released in forming bonds in the products than is needed to break bonds in the reactants
overall heat energy is given out
For both endothermic and exothermic processes:
a) breaking or making bonds?
b) increasing or decreasing temperatue of reaction?
a) endothermic: breaking bonds
exothermic: making bonds
b) endothermic: decreasing
exothermic: increasing
