Energy Changes Flashcards
What is an Exothermic Reaction?
One which transfers energy to the surroundings, usually by heating. Shown by a rise in temperature.
Examples of Burning Fossil Fuels
> Combustion of fuels
Neutralisation Reactions
Oxidation Reactions
Daily uses-handwarmers, self heating cans
What is an Endothermic Reaction?
An endothermic is one which takes in energy from the surroundings.
Examples of an Endothermic Reaction?
> Thermal Decomposition
Reaction between citric acid + Sodium hydrogen carbonate.
Everyday Uses:
> Sports injury pack
Instant Cooler
What is the problem with energy measurements?
> A lot of energy is lost to the surroundings
How do you reduce energy dissipation?
> Put a big polystyrene cup into a beaker of cotton wool
This it to give more insulation and put a lid on the top to reduce energy loss.
Describe the practical of Temperature Changes?
1)Put 25cm of 0.25mol/dm of HCL and NaHCl in separate beakers.
2)Place the beakers in a water bath set to 25degrees until they’re both at the same temperature.
3)Add the HCl followed by the NaOH to a polystyrene cup with a lid.
4)Take the temperature of the mixture every 30 seconds.
5)Repeat steps 1-4 using different volume.
Describe the Trend?
> As we increase the volume, the maximum temperature increases.
However at a certain point volume, the maximum temperature reached starts to decrease
At this point were adding too much NAOH that there isn’t much HCl.
What is Bond Energy?
Energy required to break and make bonds.
