Energy Changes Flashcards

1
Q

State the law of conservation of energy.

A

Energy cannot be created or destroyed, it can only transferred from one place to another.

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2
Q

How does the law of conservation of energy apply to chemistry?

A

In all chemical reactions, energy is either transferred to the surroundings or from the surroundings.

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3
Q

What is an exothermic reaction?

A

A reaction where energy is transferred to the surroundings.

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4
Q

Give two examples of exothermic reactions.

A

Combustion, respiration

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5
Q

What happens to the temperature of the surroundings during an exothermic reaction?

A

They increase. The thermometer is included in “the surroundings” so shows the temperature increasing.

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6
Q

What is an endothermic reaction?

A

A reaction where energy is transferred from the surroundings.

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7
Q

Give two examples of endothermic reactions.

A

Thermal decomposition reactions, citric acid and sodium hydrogencarbonate.

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8
Q

What happens to the temperature of the surroundings during an endothermic reaction?

A

They decrease. The thermometer is included in “the surroundings” so shows the temperature decreasing.

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9
Q

State two uses of exothermic reactions

A

Self-heating cans, hand warmers

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10
Q

State two uses of endothermic reactions

A

Some cooling sports injury packs

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11
Q

What are reactants?

A

The substances involved in a chemical reaction

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12
Q

What are products?

A

The substances formed when reactants have a chemical reaction

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13
Q

What is a reaction profile?

A

A diagram which shows whether the reactants have more or less energy than the products.

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14
Q

If the reactants have more energy than the products, what kind of a reaction must have taken place?

A

An exothermic one. The missing energy has been transferred to the surroundings.

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15
Q

If the reactants have less energy than the products, what kind of a reaction must have taken place?

A

An endothermic one. The extra energy has been take in by the surroundings.

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16
Q

Is breaking bonds endothermic or exothermic?

A

Endothermic. Chemical bonds are strong so require energy to break (like when you have to put energy in to separate magnets from each other)

17
Q

Is making bonds endothermic or exothermic?

A

Exothermic. Energy is released when chemical bonds are formed (like how two magnets move together when close and generate kinetic energy)

18
Q

How do we work out the overall energy change of a reaction?

A

Work out the difference between the energy needed to break all the bonds in the reactants and the energy released to form all the bonds in the products.