Exothermic and endothermic reactions Flashcards
(28 cards)
What happens when a chemical reaction occurs
There are changes in energy
… store a … amount of …, and … chemical store different …
Chemicals store a certain amount of energy, and different chemical store different amounts
What has happened if the products of a reaction store more energy than the original reactants
They have … in the … in … between the products and … from the … during the …
They have taken in the difference in energy between the products and reactants from the surroundings during the reaction
What happens if the products store less energy than the original reactants
… must have been … to the … during the …
Energy must have been transferred to the surroundings during the reaction
What is the rule about energy
Energy cannot be created nor destroyed, only transferred
What is an Exothermic reaction
A reaction that transfers energy to the surroundings
What is an endothermic reaction
A reaction that takes in energy from the surroundings
How are Exothermic reactions shown
By a rise in temperature
Is combustion endo or exothermic
Exothermic, is requires burning fuels which gives out a lot of energy
Is a neutralisation (acid + alkali) reaction endo or exothermic
Exothermic
Are oxidation reactions endo or Exothermic
They are mainly exithermic
Examples of everyday Exothermic things
-hand warmers
-self heating cans
Is thermal decomposition endo or exothermic
Endothermic
How are endothermic reactions shown
By a fall in temperature
Examples of everyday endothermic things
-sports injury packs
-instant coolers
Is melting endo or exothermic
Endothermic
Is freezing endo or exothermic
Exothermic
Practical to find energy transferred
1.put …cm3 of a certain … of … and … hydroxide in … beakers
2.place the … in a water … set to …oc, until they are … the same …
3. Add …, then … to polystyrene … with a …
4.take the … of the … every … seconds and record the … temp
5. … steps 1-… using different … of …
1.put 25cm3 of a certain conc of HCl and sodium hydroxide in separate beakers
2.place the beakers in a water bath set to 25oc, until they are both the same temperature
3. Add HCl, the NaOH to polystyrene cup with a lid
4.take the temperature of the mixture every 30 seconds and record the highest temp
5. Repeat steps 1-4 using different conc of HCl
What do reaction profiles show
The … energies of the … and products in a … and how the … changes over the … of the …
The relative energies of the reactants and products in a reaction and how the energy changes over the course of the reaction
What type of reaction is it if the products are at a lower energy than the reactants
Exothermic
What type of reaction is it if the products are at a higher energy level than the reactants
Endothermic
What does the difference in height of a reaction profile show
The overall energy change
What does the rise from reactants to the highest point represent
The activation energy (Ea)
What goes along the x and y axis of a reaction profile
X energy
Y progress of reaction
