Energy Changes Flashcards

1
Q

What are examples of exothermic reactions?

A
  • Combustion
  • Many oxidation reactions
  • Neutralisation
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2
Q

What are examples of endothermic reactions?

A
  • Thermal decomposition
  • Citric acid + sodium hydrogen carbonate
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3
Q

What happens during an exothermic reaction?

A

Energy is transferred to the surroundings and the temperature of the surroundings increases if energy is transferred by heating.

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4
Q

What happens during an endothermic reaction?

A

Energy is transferred from the surroundings and the temperature of the surroundings decreases if energy is transferred by heating.

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5
Q

Required Practical: Exothermic and Endothermic

A
  1. Place the polystyrene cup inside the glass beaker to make it more stable. This is called a calorimeter.
  2. Measure an appropriate volume of each liquid, eg 25 cm3.
  3. Place one of the liquids in a polystyrene cup.
  4. Record the temperature of the solution.
  5. Add the second solution and record the highest or lowest temperature obtained.
  6. Change your independent variable and repeat the experiment. Your independent variable could be the concentration of one of the reactants, or the type of acid/alkali being used, or the type of metal/metal carbonate being used.
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6
Q

What do reaction profiles represent?

A

The energy changes during a chemical reaction.

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7
Q

What is activation energy?

A

The minimum amount of energy needed for a reaction to happen.

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8
Q

What has to happen for a chemical reaction to happen?

A
  • Reactant particles must collide with each other
    and
  • They must have enough energy
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9
Q

What is the reaction profile for an exothermic reaction?

A
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10
Q

What is the reaction profile for an endothermic reaction?

A
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11
Q

Where does energy get transferred to during a chemical reaction?

A
  • To the reactants in order to break bonds
  • To the surroundings when bonds form in the products.
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12
Q

What is a bond energy?

A

The amount of energy needed to break one mole of a given type of covalent bond.

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13
Q

What are the endothermic/exothermic processes that happen as a chemical reaction happens?

A
  • energy is supplied to break bonds in the reactants - endothermic
  • Energy is released when bonds form in the products - exothermic
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14
Q

If the overall energy change is positive the reaction is …

A

Endithermic

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