Energy Changes Flashcards

1
Q

What is a exothermic reaction?

A

A reaction where energy is transferred to the surroundings so surrounding temperature increase (combustion, oxidation and reduction) - energy released from forming bonds is greater than that needed to break the bonds

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2
Q

What is an endothermic reaction?

A

Where energy is taken from the surroundings so surrounding temperature decreases (thermal decomposition) - energy needed to break bonds is greater than energy released making them

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3
Q

What is activation energy?

A

Minimum amount of energy particles need to react

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4
Q

What happens in a chemical reaction in terms of bond energies?

A

Energy is supplied to break bonds and energy is released when bonds are made.

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5
Q

How do you find the total energy of reaction?

A

Energy of reaction = sum of bonds broken – sum of bonds made

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6
Q

What is a cell?

A

A cell is composed of two electrodes dipped in an electrolyte solution. It produces electricity from a chemical reaction.

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7
Q

What is a battery?

A

A battery consists of two or more cells connected in series.

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8
Q

What is a rechargeable cell?

A

Chemical reactions are reversed when an external current is supplied

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9
Q

What is a non-rechargeable cell?

A

Reactants are used up, cannot be recharged

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10
Q

What is a fuel cell?

A

Fuel cells are supplied by fuel and oxygen to oxidise the fuel to generate electricity.

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11
Q

What are the advantages and disadvantages of hydrogen fuel cells?

A

Advantages: no pollutants, no recharging

Disadvantages: flammable, H2 difficult to store, fossil fuel production, toxic chemicals, expensive production of H2 by electrolysis

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