Chemistry - Chem 8: Energy changes during chemical reactions

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What do all material substances contain?
chemical potential energy
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What is the ocnsevration of energy?
energy cannot be created or destroyed, only changed from one form to another
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During chemical reactions heat is...
... given out to the surroundings or taken in from the surroundings
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What happens during an exothermic reactions?
heat is given out, the temperature of the surrounding solution rises
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What happens during an endothermic reaction?
heat is take in, the temperature of the surrounding solution falls
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What defines temperature change?
final temp - intial temp
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What is the cpe of the products in an exothermic reaction and endothermic reaction? What is the energy change?
the cpe of the products is less that that of the reactants. energy change is negative. endothermic is vice versa
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What is the unit for energy chagne?
kJ/mol
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How do you define energy change?
final energy - intial energy
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What is concentration?
the amount of a solute chemical (grams or moles) in a given volume of solution (cubic decimetre)
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What is the formula for concentration?
conc. (mol/dm3 or M) = no. of moles/ volume (dm3)
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How do you define temperature change?
final temp -initial temp
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What is the temperature change in exothermic and endothermic reactions?
temp. - up for exo, temp. down - endo
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How do you calculate energy change?
E=mas of water * specific heat capacity * corrected temperature change, convert the energy into kilojoules and calculate what one mole is. insert sign for enod or exo
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What is the density and specific heat capacity of water?
1g/cubic cm and 4.2J/g/C
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Describe fuels
substances that give out heat when they burn (combustion is exothermic)
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What are the products of burning hydrocarbons?
carbon dioxide (greenhouse gas) and water
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Name some other pollutants fuels give out
carbon monoxide - toxic, nitrogen oxides - acid rain, sulphur dioxide - acid rain, carbon particles - asthma
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What do foods contain?
energy , fatty foods - most energy, 1 kilocalorie - 4.2 kilojoules
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What does breaking bonds and making bonds do?
breaking bonds 0 takes in energy; making bonds - releases energy
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What is bond energy?
the energy needed to break one mole of a particular covalent bond
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What process is breaking bonds and making bonds?
breaking bonds - endothermic (+), making bonds - exothermic (-)
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How else may we calculate energy change?
using average bond energies - energy absorbed + energy released
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What are renewable and non-renewable sources of energy?
renewable - sources of energy that will never run out, non-renewable - will run out
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When fuels produce energy, what happens?
they are consumed
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What are renewable fuels?
fuels that will never run out
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Card 2

Front

What is the ocnsevration of energy?

Back

energy cannot be created or destroyed, only changed from one form to another

Card 3

Front

During chemical reactions heat is...

Back

Preview of the front of card 3

Card 4

Front

What happens during an exothermic reactions?

Back

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Card 5

Front

What happens during an endothermic reaction?

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