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Chemistry > GCSE - Topic 1 and 2 - Ideas About Atoms & Hydrocarbons and Atmosphere - Year 10 > Flashcards

GCSE - Topic 1 and 2 - Ideas About Atoms & Hydrocarbons and Atmosphere - Year 10 Flashcards

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1
Q

What happens to energy in a chemical reaction?

A

It moves around.

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2
Q

What do chemicals store? How does it change depending on the chemical?

A

Chemicals store a certain amount of energy - and different chemicals store different amounts.

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3
Q

If the products of a reaction store more energy than the original reactants, then what must have happened?

A

Then they must have taken in the difference in energy between the products and reactants from the surroundings during the reaction.

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4
Q

If the products of a reaction store less energy than the original reactants, then what must have happened?

A

If they store less, then the excess energy was transferred to the surroundings during the reaction.

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5
Q

How does the overall amount of energy change in a reaction?

A

It doesn’t change. Energy is conserved in reactions (can’t be created or destroyed).

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6
Q

Exothermic Reaction

A

A reaction that transfers energy to the surroundings, usually by heating. This is shown in a rise in temperature.

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7
Q

Give an example of an exothermic reaction.

A

Burning fuels (a.k.a combustion), neutralisation reactions (acid + alkali), many oxidation reactions.

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8
Q

How can you tell that adding sodium to water is an exothermic reaction?

A

Sodium moves on the surface as it is oxidised.

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9
Q

Endothermic Reaction

A

A reaction that takes in energy from the surroundings. This is shown by a fall in temperature.

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10
Q

Give an example of an endothermic reaction.

A

Thermal decomposition and, the reaction between citric acid and sodium hydrogencarbonate.

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11
Q

What are the steps for the measuring energy transfer practical?

A
  1. Put 25^3 of 0.25 mol/dm^3 of hydrochloric acid and sodium hydroxide in separate beakers.
  2. Place the beakers in a water bath set to 25C until they are both at the same temperature (25C).
  3. Add the HCl followed by the NaOH to a polystyrene cup with a lid.
  4. Take the temperature of the mixture every 30 seconds, and record the highest temperature.
  5. Repeat steps 1-4 using 0.5 mol/dm^3 and then 1 mol/dm^3 of hydrochloric acid.
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12
Q

How can you measure the amount of energy released by a chemical reaction (in solution)?

A

Take the temperature of the reagents, mix them in a polystyrene cup and measure the temperature of the solution at the end of the reaction.

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13
Q

What’s the biggest problem with energy measurements?

A

Energy lost to the surroundings.

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14
Q

Whilst measuring the amount of energy released by a chemical reaction, how can you reduce the energy lost to the surroundings?

A

You can reduce it a bit by putting the polystyrene cup into a beaker of cotton wool to give more insulation, and putting a lid on the cup to reduce energy lost by evaporation.

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15
Q

What types of reactions does the measuring energy released in a chemical reaction practical work for?

A

Neutralisation reactions, or reactions between metals and acids, or carbonates and acids.

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16
Q

What are reaction profiles?

A

Diagrams that show the relative energies of the reactants and products in a reaction, and how the energy changes over the course of the reaction.

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17
Q

In a reaction profile, what does a decrease in height represent?

A

The overall energy change in the reaction (the energy given out) per mole.

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18
Q

In a reaction profile, what does an exothermic reaction look like?

A

When the products are at a lower energy than the reactants.

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19
Q

In a reaction profile, when it displays an exothermic reaction, what does the initial rise in energy represent?

A

The activation energy.

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20
Q

What is the activation energy?

A

The minimum amount of energy the reactants need to collide with each other and react.

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21
Q

What can reaction profiles also be called?

A

Energy level diagrams.

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22
Q

How could the activation energy be supplied in an exothermic reaction?

A

By heating the reaction mixture.

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23
Q

In a reaction profile, what does an endothermic reaction look like?

A

When the products are at a highers energy than the reactants.

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24
Q

In a reaction profile, what does an increase in height represents?

A

The difference in height represents the overall energy change in the reaction (the energy taken in) per mole.

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25
Q

Is breaking a bond exothermic or endothermic?

A

Endothermic.

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26
Q

Is forming a bond endothermic or endothermic?

A

Exothermic.

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27
Q

What happens to bonds during a chemical reaction?

A

Old bonds are broken and new bonds are formed.

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28
Q

What needs to be supplied to break existing bonds?

A

Energy.

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29
Q

What is released when new bonds are formed?

A

Energy.

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30
Q

In exothermic reactions, is the energy released by forming bonds greater or less than the energy used to break them?

A

Greater than.

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31
Q

In endothermic reactions, is the energy used to break bonds greater than or less than the energy released by forming them?

A

Greater than.

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32
Q

Every chemical bond has a particular ___ energy associated with it.

A

bond

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33
Q

Bond energies vary slightly, depending on what?

A

The compound the bond occurs in.

34
Q

What can you use known bond energies to calculate?

A

The overall energy change for a reaction.

35
Q

In bonds, how do you work out the overall energy change?

A

The sum of the energies needed to break bonds in the reactants minus the energy released when the new bonds are formed in the products

36
Q

In reversible reactions, if the reaction is endothermic in one direction, will it be exothermic or endothermic in the other.

A

It will be exothermic in the other.

37
Q

What type of reactions can be both endothermic and exothermic?

A

Reversible reactions.

38
Q

How can reversible reactions be endothermic and exothermic?

A

The energy transferred from the surroundings by the endothermic reaction is equal to the energy transferred to the surroundings during the endothermic reaction.

39
Q

What’s an indicator?

A

A dye that changes colour depending on whether it’s above or below a certain pH.

40
Q

What’s an acid?

A

A substance that forms aqueous solutions with a pH of less than 7.

41
Q

What’s a base?

A

A substance with a pH greater than 7.

42
Q

What’s an alkali?

A

A base that dissolves in water to form a solution with a pH greater than 7.

43
Q

What do alkalis form in water?

A

OH^- ions.

44
Q

Neutralisation Reaction

A

acid + base -> salt + water

H^+ (aq) + OH^- (aq) -> H20 (l)

45
Q

What can the neutralisation of strong acids and alkalis be used to calculate?

A

The concentration of an acid or alkali by titration.

46
Q

What happens to acid in an aqueous solution?

A

They ionise, they produce hydrogen ions, H^+.

47
Q

What is a H^+ ion?

A

A proton.

48
Q

Do strong acids ionise completely in water?

A

Yes. All acid particles dissociate to release H^+ ions.

49
Q

Do weak acids ionise completely in solution?

A

No, they don’t fully ionise. Only a small proportion of acid particles dissociate to release H^+ ions.

50
Q

The ionisation of a weak acid is a ____ reaction, which sets up an ____ between the _____ acid and _____ acid.

A

The ionisation of a weak acid is a reversible reaction, which sets up an equilibrium between the undissociated and dissociated acid.

51
Q

The rate of reaction will be faster if the concentration of H^+ ions is ____.

A

higher

52
Q

Will stronger acids or weaker acids of the same concentration be more reactive?

A

Stronger acids because the concentration of H^+ ions is higher.

53
Q

What is pH the measure of?

A

The concentration of hydrogen ions in the solution.

54
Q

What is acid strength?

A

The proportion of the acid molecules that ionise in water.

55
Q

What is the concentration of acid?

A

Concentration measure how much acid there is in a certain volume of water. Basically, it’s how watered down your acid is.

56
Q

The larger the amount of acid there is in a certain volume of liquid, the ___ concentrated the acid is.

A

more

57
Q

Acid + Metal Oxide ->

A

Salt + Water

58
Q

Acid + Metal Hydroxide ->

A

Salt + Water

59
Q

Hydrochloric acid + Copper oxide ->

Sulfuric acid + Potassium hydroxide ->

Nitric acid -> Sodium hydroxide ->

A

Copper Chloride + Water

Potassium Sulfate + Water

Sodium Nitrate + Water

60
Q

Do metal oxides and metal hydroxides dissolve in water?

A

Some do. These soluble compounds are alkalis

61
Q

Will bases that won’t dissolve in water still take part in the neutralisation reaction with acids?

A

Yes.

62
Q

Are metal carbonates bases or acids?

A

Bases.

63
Q

Acid + Metal Carbonate ->

A

Salt + Water + Carbon Dioxide

64
Q

Hydrochloric acid + Sodium carbonate ->

Sulfuric acid + Calcium carbonate ->

A

Sodium chloride + Water + Carbon dioxide

Calcium sulfate + Water + Carbon dioxide

65
Q

What are the steps for making a soluble salt using an insoluble base (practical)?

A
  1. Pick the right acid and insoluble base, such as an insoluble metal oxide, hydroxide or carbonate.
  2. Gently warm the dilute acid using a bunsen burner, then turn off the bunsen burner.
  3. Add the insoluble base to the acid a bit at a time, until no more reacts (the base is in excess).
  4. Then, filter out the excess solid to get the salt solution.
  5. To get pure, solid crystals of salt, gently heat the solution using a water bath or an electric heater to evaporate some of the water (to make it more concentrated) and then stop heating it and leave the solution to cool. Crystals of the salt should form, which can be filtered out of the solution and then dried. This is called crytilisation.
66
Q

How can you know when all of the acid has been neutralised in a reaction?

A

When, even after stirring, the excess solid will just sink to the bottom of the flask.

67
Q

How is reactivity determined for metals?

A

By how easily they lose electrons - forming positive ions.

68
Q

When metals react with water or acid, they ___ electrons.

A

lose

69
Q

What is the reactivity series?

A

Putting the metals in order of reactivity from most to least reactive.

70
Q

Reactivity Series (list them)

A

Potassium
Sodium
Lithium
Calcium
Magnesium
Carbon (non-metal)
Zinc
Iron
Hydrogen (non-metal)
Copper

71
Q

Acid + Metal ->

A

Salt + Hydrogen

72
Q

Metal + Water ->

A

Metal Hydroxide + Hydrogen

73
Q

How can you investigate the reactivity of metals with acids?

A
  1. Measure the temperature change of the reaction with an acid or water over a set time period. If you use the same mass and surface area of metal each time, then the more reactive the metal, the greater the temperature change should be.
  2. The speed of the reaction is indicated by the rate at which the bubbles of hydrogen are given off.
74
Q

Chlorine test and the result?

A

Chlorine bleaches damp litmus paper, turning it white. (It may turn red for a moment first though - that’s because a solution of chlorine is acidic.)

75
Q

Oxygen test and the result?

A

If you put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint.

76
Q

Carbon dioxide test and the result?

A

Bubbling carbon dioxide through (or shaking carbon dioxide with) an aqueous solution of calcium hydroxide (known as limewater) causes the solution to go from clear to cloudy.

77
Q

Hydrogen test and the result?

A

If you hold a lit splint at the open end of a test tube containing hydrogen, you’ll get a “squeaky pop”. (The noise comes from the hydrogen quickly burning with the oxygen air to form H20).

78
Q

At the start of the 19th century ___ ___ described atoms as ___ ___, and said that ___ ___ made up the ___ ___.

A

At the start of the 19th century John Dalton described atoms as solid spheres and said that different spheres made up the different elements.

79
Q

In 1897 __ ___ concluded from his experiments that atoms ___ solid spheres. His measurements of ___ and __ showed that an atom must contain __ ___, ___ ___ ___ - ___. The ‘solid sphere’ idea of atomic structure had to be ___. The new theory was known as the ‘__ ___ __’.

A

In 1897 J J Thompson concluded from his experiments that atoms weren’t solid spheres. His measurements of charge and mass showed that an atom must contain even smaller, negatively charged particles - electrons. The ‘solid sphere’ idea of atomic structure had to be changed. The new theory was known as the ‘plum pudding model’.

80
Q

What did the plum pudding model show the atom as?

A

A ball of positive charge with electrons stuck in it.

Chemistry (3 decks)

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