C11 Energy Changes Flashcards

1
Q

What is an exothermic energy transfer?

A

transfer to surrounding
(gets hotter)

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2
Q

Example of exothermic energy transfers

A

Oxidation
Combustion
Neutralisation

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3
Q

What is an endothermic energy transfer?

A

Transfer from the surroundings to the object
(gets colder)

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4
Q

Example of endothermic energy transfers

A

Thermal decomposition
Sports injury packs

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5
Q

What is a reaction profile?

A

Diagram showing how the energy changes in a reaction

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6
Q

What is the activation energy?

A

Minimum amount of energy required before a collision will result in a reaction

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7
Q

What can be used to lower the activation energy?

A

Catalysts

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8
Q

What is bond energy?

A

Energy required to break a bond

OR

The energy released when a bond is formed

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9
Q

In terms of bonds what is an exothermic reaction?

A

LESS energy is required to break the bonds than is released when making the bonds

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10
Q

In terms of bonds what is an endothermic reaction?

A

MORE energy is required to break the bonds than is released when making the bonds

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11
Q

How are chemical cells made?

A

Connect two different metals (electrodes) in a solution (electrolytes)

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12
Q

What is a battery?

A

Two or more chemical cells connected in series

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13
Q

How does the p.d of a cell depend on metals that the electrodes are made of?

A

Bigger the difference in reactivity, the greater the p.d

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14
Q

How can some cells be recharged?

A

By applying an external current

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15
Q

Why can some cells not be recharged?

A

The reaction cannot be reversed

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16
Q

What is a fuel cell?

A

Cell that uses a fuel and oxygen to generate electricity

17
Q

In a hydrogen fuel cell, what is the overall reaction?

A

2H2 + O2 —> 2H2O

18
Q

Advantage of a hydrogen fuel cell

A

only product is water

does not need to be electrically recharged

19
Q

Disadvantages of hydrogen fuel cells

A

-Hydrogen is flammable
-Difficult to store
-Produced from non-
renewable sources