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Chemistry Core Knowledge C3 and C4 > C5 > Flashcards

C5 Flashcards

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1
Q

What is an exothermic reaction?

A

A reaction that gives OUT heat energy.

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2
Q

What is an endothermic reaction?

A

A reaction that TAKES in heat energy.

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3
Q

Give three examples of exothermic reactions.

A

Combustion
Respiration
Neutralisation

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4
Q

What happens to the temperature of the surroundings (as shown on a thermometer) in an exothermic reaction.

A

Temperature goes up

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5
Q

What uses are there for exothermic reactions?

A

Fuels being combusted for heat
Self-heating cans
Hand-warmers

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6
Q

State a use for endothermic reactions.

A

Sport injury packs

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7
Q

What must happen for a reaction to happen?

A

Reactant particles must collide with enough energy - (activation energy)

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8
Q

What is meant by the term activation energy.

A

The minimum energy needed for a reaction to start.

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9
Q

Is the breaking of bonds exothermic or endothermic?

A

Endothermic

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10
Q

Is the making of bonds exothermic or endothermic?

A

Exothermic

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11
Q

Why is a reaction exothermic?

A

Less heat energy is needed to break bonds than the heat energy given out.

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12
Q

Why is a reaction endothermic?

A

Less energy is released in making bonds in the products than is required in breaking bonds in the reactants.

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13
Q

How do you calculate the energy change in a reaction?

A

Energy created from bonds - energy needed to break bonds

Negative answer = exothermic
Positive answer = endothermic

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14
Q

How do cells produce electricity?

A

The chemicals in them react.

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15
Q

What is a simple cell?

A

2 different metals and an electrolyte.

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16
Q

When will 2 metals in a cell produce a bigger voltage?

A

If they have a wider gap in their reactivities.

17
Q

What is a battery?

A

2 or more cells connected in a series

18
Q

Why do non rechargeable batteries like alkaline batteries run out?

A

When one of the reactants is used up the chemical reaction stops

19
Q

Why can rechargeable batteries be recharged?

A

The chemical reaction is reversed when a current is applied to make the original reactants again.

20
Q

What do fuel cells use to produce electricity?

A

A fuel (hydrogen) and oxygen.

21
Q

What is the overall equation for the reaction in a hydrogen fuel cell?

A

2H(2) + O(2) ——-> water

22
Q

What is an advantage of a fuel cell over a rechargeable cell?

A

Fuels can be supplied constantly to generate electricity

23
Q

What is a disadvantage of a fuel cell over a rechargeable cell?

A

Hydrogen is flammable

24
Q

Give 2 examples of endothermic reactions.

A

Photosynthesis

Thermal decomposition

Chemistry Core Knowledge C3 and C4 (4 decks)

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