Chemical Energetics
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What are exothermic reactions?
Chemical reactions in which heat is given out
What is bond forming an example of?
Exothermic reaction
What are the energy changes that occur during an exothermic reaction?
Energy released is more than the energy absorbed
Bond forming __ energy
releases
What happens to heat during an exothermic reaction?
Heat is given out and transferred from the chemical to surrounding
What happens to the temperature of the mixture during an exothermic reaction?
Temperature of mixture will rise until the highest temperature is reached, then fall to room temp.
What are the energy transformations that occur during an exothermic reaction?
Transfer chemical to heat energy
What are three common examples of exothermic reactions?
Combustion of fuels Rusting iron Metal corroding Neutralisation between acid and alkali Respiration
What are endothermic reactions?
Chemical reactions in which heat is absorbed/taken in
What is bond breaking an example of?
Endothermic reaction
What are the energy changes that occur during an endothermic reaction?
Energy absorbed is more than the energy released
Bond breaking __ energy
requires
What happens to heat during an endothermic reaction?
Heat is absorbed and transferred from surroundings to reactants
What happens to the temperature of the mixture during an endothermic reaction?
Temperature of mixture falls until lowest temp is reached, then rise until room temp
What are the energy transformations that occur during an exothermic reaction?
Transfer heat to chemical energy
What are common examples of endothermic reactions? (2)
Photosynthesis Thermal decomposition
What is a fuel?
substance that can be burned to release energy
What happens when fuel is burned/ the combustion of fuel? (2)
Energy is stored inside the fuel, burning the fuel releases it Combustion reactions turns fuel and oxygen into water and carbon dioxide (and releases energy)
Why is hydrogen used as a fuel?
Its environmentally friendly
What happens in a hydrogen fuel cell?(2)
In hydrogen fuel cell, hydrogen reacts with oxygen without burning Energy released is used to generate electricity (which is used to drive an electric motor)
What are three advantages of fuel cells?
Lightweight High efficiency Only water is made – no additional pollutants
How are radioisotopes used a source of energy?
These isotopes are used to produce nuclear fuels
What are 2 common radioisotopes used as a source of energy?
Urainium235 Plutonium239
What are the products that would be released if petrol and natural gas (methane) were used in energy production?
Carbon dioxide and water