Chemistry Topic 5 Flashcards
What does reactants and products mean?
Reactants- bonds are broken
Products- bonds are made
What is an endothermic reaction?
Reactions where reactants take energy in from the surroundings (and the temperatures of the surroundings decrease)
What is an exothermic reaction?
When reactants release energy out to the surroundings during the reaction (and the temperature of the surroundings increase)
Give examples of exothermic reactions:
-combustion
-neutralisation
Give examples of exothermic reactions:
-thermal decomposition
-photosynthesis
How do you know when the reaction profile is exothermic?
The products have less energy than the reactants as energy was transferred to the surroundings during the reaction
How do you know when the reaction profile is endothermic?
The products have more energy than the reactants as the energy was transferred to the reactants from the surroundings during the reaction
Bond breaking =
Endothermic
Bond making=
Exothermic
What are chemical cells?
The use of chemical reactions to transfer energy by electricity
What are the two types of chemical cells?
Rechargeable and non-rechargeable
What are rechargeable cells?
Can be recharged by reversing the external current
What are non-rechargeable cells?
Cannot be recharged as the reaction stops when one of the reactants is used up; the reaction is then irreversible
What are fuel cells?
Produces a voltage continuously when supplied with a fuel and oxygen; fuel is oxidised electrochemically, rather than it being burnt
What is an electrode?
A solid conductor that carries an electric current into non-metallic substances
What is an electrolyte?
An ionic compound that is molten or dissolved in water that conducts electricity and is decomposed by it
What happens to voltage when there is a higher difference in the reactivity of the 2 electrodes?
Voltage is greater (•produced by the chemical cell)
What happens to the voltage when there is a lower difference between the 2 electrodes?
The voltage is lower (•produced by the chemical cell)
What happens to negative electrodes (cathode)?
Reduction reaction happens. - positively charged ions gain electrons
What happens to positively charged electrodes (anodes)?
Positively charged ions move towards the cathode. - oxidation happens (loss of electrons)
