C7 Flashcards
Activation energy
The minimum energy needed for a reaction to take place
Bond energy
The energy required to break a specific chemical bond
Endothermic reaction
A reaction that takes energy from the surroundings
Exothermic reaction
A reaction that transfers energy to the surroundings
Reaction profile
Diagrams that show the relative energies of the reactants and products in a reaction
Aim of investigating temperature changes required practical
To investigate the variables that affect temperature changes in reacting solutions
Equipment for required practical (investigating temperature changes)
Polystyrene cup, thermometer, 250 cm3 glass beaker, measuring cylinder, top pan balance
Method for reacting 2 solutions (acid and alkali)
Place polystryrene cuo inside glass beaker, measure 25cm3 of each liquid, place one of liquids in polystyrene cup, record temp of solution, add second solution and record highest or lowest temperature, change independant variable and repeat experiment
Possible harms of RP
may irritate skin or eyes so could wear gloves or goggles
What does a reaction profile show
The relative energy of the reactants and products and the energy changes during a reaction.
What reaction is it when the reactants have more energy than the products
Exothermic
What reaction is it when the reactants have less energy than the products
Endothermic
What percentage of reactions are exothermic and endothermic
90% exothermic and 10% endothermic
Examples of exothermic reactions
Combustion reactions, most neutralisation
Uses of exothermic reactions
Self heating cans and hand warmers
Examples of endothermic reactions
Thermal decomposition, the reaction of citric acid and sodium hydrocarbonate
Use of endothermic reaction
Instant ice packs to treat a sports injury
In a reaction profile for an exothermic reaction, what does the diagram show
The reactants of the chemical equation having more energy than the products (line goes down)
In a reaction profile for an endothermic reaction, what does the diagram show
The products to have more energy than the reactants
Diagram goes up to down
How do exothermic reacts link to animals?
All warm-blooded animals rely on exothermic reactions in respiration to keep their body temp steady
Example of thermal decomposition:
-Decomposition of calcium carbonate.
-When heated, it forms calcium oxide and carbon dioxide
-the calcium carbonate needs to absorb energy from the surroundings to be broken down
When can you feel an endothermic reaction?
When you eat a sherbet sweet you can feel the sherbet dissolving in the water in your mouth takes in energy
Bond breaking
Energy has to be supplied to break chemical bonds (endothermic)
Bond making
Energynis transferred to the surroundings (exothermic)
