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Chemistry > C5 - Energy Changes > Flashcards

C5 - Energy Changes Flashcards

1
Q

what is an exothermic reaction

A

one that transfers energy to the surroundings so the temp increases

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2
Q

what are examples of an exothermic reaction

A

combustion
many oxidation reactions
neutralisation

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3
Q

everyday uses of exothermic reactions

A

self heating cans
hand warmers

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4
Q

what are endothermic reactions

A

one that takes in energy from the surroundings so the temp decreases

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5
Q

examples of endothermic reactions

A

thermal decompositions
citric acid and sodium hydrocarbonate

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6
Q

everyday use of exothermic reactions

A

sports injury pack

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7
Q

when do chemical reactions occur

A

when particles collide with sufficient energy

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8
Q

what is the activation energy

A

the minimum amount of energy particles must have to react

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9
Q

during chemical reactions, does breaking bonds require energy or release it

A

it requires energy

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10
Q

during chemical reactions, does making bonds require energy or release it

A

release it

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11
Q

what is the fuel for fuel cells

A

an external source such as hydrogen or oxygen in the air

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12
Q

what happens to the fuel in the fuel cell

A

its oxidised electrochemically within the fuel cell to produce a potential difference

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13
Q

what is the overall reaction in a hydrogen fuel cell

A

oxidation of hydrogen to produce water

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14
Q

what do hydrogen fuel cells provide an alternative to

A

rechargable cells and batteries

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15
Q

what do cells contain

A

chemicals which react to produce electricity

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16
Q

what is the voltage produced by the cell controlled by

A

type of electrode and electrolyte

17
Q

how can a simple cell be made

A

connecting two different metals in contact with an electrolyte

18
Q

what do batteries consist of

A

two or more cells connected together in a series to produce a greater voltage

19
Q

what is an example of non rechargeable batteries

A

alkaline batteries

20
Q

why are non rechargable batteries non rechargable

A

as the chemical reactions stop when one of the reactants has been used up

21
Q

why are rechargable batteries rechargable

A

as the chemical reactions can be reversed when an electric current is applied to them

Chemistry (5 decks)

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