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C5 End of Topic - Coggle Diagram
C5 End of Topic
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Fuel Cells
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Hydrogen fuel cells produce a potential difference via the oxidation of hydrogen (hydrogen loses electrons).
Required Practical 4
The purpose of this practical is to observe the variables that affect temperature changes in chemical reactions
The reaction that will take place within this practical is an exothermic, neutralisation reaction between hydrochloric acid and sodium hydroxide.
Independant variable: Volume of sodium hydroxide solution.
Dependant variable: Maximum temperature reached.
Control variable: Volume of hydrochloric acid and concentrations of solutions used.
First, the hydrochloric acid must be transferred into a polystyrene cup, this make sure that minimum amount of heat is lost.
The cup will then be placed into a breaker to ensure the acid does not spill.
The temperature of the acid must then be recorded using a thermometer in order to measure temperature change later.
A small amount of sodium hydroxide solution will then be transferred from a measuring cylinder to the cup and a lid will be placed on the cup.
The thermometer will then be used to gently stir the solution.
When the highest reached temperature of the solution is reached, record the temperature.
The polystyrene cup will then be emptied and rinsed out, the experiment will then be repeated with a larger volume of sodium hydroxide.
A positive temperature increase should be observed, this means that the system has lost energy due to an exothermic reaction.
Cells and Batteries
Within chemical cells, two metals with a larger difference in reactivity will produce a greater voltage
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Alkaline batteries are not rechargeable because the reaction that takes place within them is irreversible
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Exothermic Reactions
Within exothermic reactions, energy is transferred from the system to the surroundings, increasing the temperature of the surroundings
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Combustion, oxidation and neutralisation are all examples of exothermic reactions
Endothermic Reactions
Thermal decomposition and the reaction between citric acid and baking soda are both endothermic reactions
Within endothermic reactions, energy is transferred from the surroundings to the system, decreasing the temperature of the surroundings
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