Exothermic&Endothermic reactions Flashcards
What is an exothermic reaction?
It is a reaction which transfers energy to its surroundings by heating , ie rise in temperature .
What is an endothermic reaction?
It is a reaction which TAKES IN heat/ energy from its surroundings , ie fall in temperature .
Name 3 types of an exothermic reaction .
Combustion- burning fuels
Neutralising reactions - acid & alkali
Oxidation reactions .
Name 2 types of endothermic reaction .
Reactions between citric acid and hydrogen carbonate
Thermal decomposition .
Name 2 everyday uses for exothermic reactions .
Hand warmers
Self hearing cans .
Name 2 endothermic everyday uses .
Sports injury packs
Hand coolers .
How is energy moved around in chemical reactions?
Chemicals store a certain amount of energy . If the products of a reaction store more energy than the original reactants then they must have taken in the amount of difference in energy in both reactants from the surroundings during the reaction . If the products store less energy the excess energy is transferred to the surroundings . The overall amount does not change this is because it has been conserved and cannot be created neither destroyed just move around .
REQUIRED PRACTICAL
Label 5 quick and easy steps for the exothermic or endothermic reactions .
1) Add 25cm3 of hydrochloride acid and sodium hydroxide in separate beakers .
2) place the beakers in a water bath till they reacts the temperature of 25 degrees
3) Then add the hydrochloric acid to a polystyrene cup with a lid placed on top and and thermometer inside .
4) Gradually add sodium hydroxide to the misfire only adding 5cm3 at a time . After that mix well and check the temperature every 30 seconds, to see wether it is a exothermic or endothermic reaction .
REQUIRED PRACTICAL
Name one insulator which will keep energy inside of the polystyrene cup and which won’t affect the reaction .
A lid - this is because it keeps all of the nervy in side of the cup and it will not be lost by evaporation
Cotton wool - insulating the cup with this will insure that all of the heat that is formed in the reaction will be able to stay in there there for it will not effect the result of the reaction .
REQUIRED PRACTICAL
Name control , dependent and independent variables for this reaction .
Control - hydrochloric acid
Dependent - acid
Independent - temperature
Graphs to show energy change ????
These are to show relative energies of the reactants and products in the reactants and to see how the energy changes over time .
