C7 Flashcards
What happens to energy in a chemical reaction?
Energy is moved around . It cannot be created or destroyed , it is conserved in chemical reactions. If a reaction transfers energy to the surroundings the product molecules will have less energy.
What is an exothermic reaction?
A reaction that transfers energy to the surroundings so the temperature of the surroundings increases
Types of exothermic reactions ?
Combustion
Manu oxidation reactions
Neutralisation
What are everyday uses of exothermic reactions ?
Hand warmers ( use exothermic oxidation of iron in air to release energy )and self heating cans(hot chocolate and coffee rely on exothermic reactions between chemicals in their bases
What is an endothermic reactions?
Reaction that takes in energy from the surroundings so the temperature of the surroundings decreases
Types of endothermic reactions?
- Thermal decomposition
- Reaction of citric acid and sodium hydrogencarbonate
- sports injury packs are based on endothermic reactions
Example of an oxidation reaction being exothermic ?
Adding sodium to water releases energy , so it must be exothermic. The reaction releases energy and sodium moves about on the surface of the water as it is oxidised.
What are reaction profiles?
Diagrams that show the relative energies of the reactants and products in a reaction and how energy changes over the course of a reaction
Draw an exothermic reaction profile ?
Draw 5 times
Draw an endothermic reaction profile ?
Draw 5 times
When do chemical reactions only occur?
When reacting particles collide with each other and with sufficient energy.
What is the activation energy ?
The minimum amount of energy that particles need to react.
What happens to bonds during a chemical reaction?
Old bonds are broken and ene bonds are formed.
What type of reaction happens when breaking bonds and why?
Endothermic as energy is supplied
What type of reaction takes place when forming new bonds and why?
Exothermic because energy is released
