What is activation energy?
The minimum amount of energy needed for a reaction to take place
What is bond energy?
The energy required to break a specific chemical bond
What is an endothermic reaction?
A reaction that takes IN energy from the surroundings
What is an exothermic reaction?
A reaction that transfers energy TO the surroundings
What is a reaction profile?
The relative difference in the energy of reactants and products
What are 3 examples of extothermic reactions?
Combustion (burning)
Oxidation
Neutralisation
What is an example of endothermic reaction?
Thermal decomposition
Draw an energy diagram for an endothermic reaction and exothermic reaction.
:)
What are we investigating in the temperature change required practical?
Investigate the temperature change in an exothermic reaction, which is the neutralisation reaction between hydrochloric acid and alkali sodium hydroxide.
What is the independent variable in the temperature change required practical?
The volume of sodium hydroxide solution
What is the dependent variable in the temperature change required practical?
Is the maximum temperature reached
What are the control variables in the temperature change required practical?
Volume of hydrochloric acid
Concentrations of both HCL and Sodium hydroxide solution
What are the step by steps to carrrying out the temperature change required practical?
1) Using a measuring cylinder measure 30cm^3 of dilute hydrochloric acid
2) Transfer the acid into a polystyrene cup
3) Place the cup in a beaker to prevent the cup from falling over
4) Use a thermometer to measure the temperature of the acid and record in a table
5) Use a measuring cylinder to measure 5cm^3 of sodium hydroxide solution.
6) Transfer the sodium hydroxide solution into the polystyrene cup
7) Place a plastic life on the cup and put the thermometer through the hole in the lid
8) Gently stir the solution with thermometer
9) When the temperature of the thermometer stops changing we record the maximum temperature reaches and rinse out the polystyrene cup
10) Repeat the experiment a number of time each time increasing the volume of sodium hydroxide solution by 5cm^3, until a maximum of 40cm3 of sodium hydroxide solution is reached
11) Repat the whole investigation twice and calculate a mean for the results, then plot a graph of the results.
What will happen as the temperature change required practical takes place?
The reaction is exothermic so it releases energy into the surroundings meaning the temperature of the solution will increase.
What is the reason to using a polystyrene cup with a lid?
This is because we want to reduce any heat losses, polystyrene is a child thermal insulator, reducing heat loss through the sides and the bottom. Lid reduces heat loss to the air.
Uses of exothermic reactions?
Self heating cans
Hand warmers
Uses of endothermic reactions?
Instant ice packs
Draw energy profiles for both endo and exo
Hehe
How are exothermic reactions shown as in bond energy calculations?
Exothermic energy changes are shown as negative because energy has been transferred from the chemicals.
How are endothermic reactions shown as in bond energy calculations?
Endothermic changes are shown as positive, because energy has been gained
What happens in exothermic reactions?
In exothermic reactions, energy is transferred from chemicals to the surroundings.
What happens in endothermic reactions?
In endothermic reactions energy is gained from the surroundings.
What happens when we break chemical bonds in terms of bond energy calculations?
When we break a chemical bond, this requires energy meaning it is endothermic
What happens when we make bonds in terms of bond energy calculations?
Making bonds release energy meaning it is exothermic.
