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GCSE Chemistry > Elements, Compounds And Mixtures > Flashcards

Elements, Compounds And Mixtures Flashcards

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1
Q

Element

A

A pure substance made of only one type of atom.

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2
Q

Compound

A

A substance made of two or more different types of atoms chemically bonded together.

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3
Q

Mixture

A

Two or more different types of atoms mixed together, NOT chemically bonded

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4
Q

Mg 2+ + Br- =

A

MgBr2

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5
Q

Mr

A

Relative formula mass

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6
Q

Ar

A

Relative atomic mass

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7
Q

Percentage composition

A

Ar of an element
————————. X 100
Mr of a compound

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8
Q

What processes can be used to separate mixtures (4)

A
  • distillation
  • chromatography
  • filtration
  • evaporation
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9
Q

Rf value

A

Distance travelled by substance
————- ———————- - ——-
Total distance travelled by solvent

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10
Q

What does chromatography separate and how

A

Separates soluble liquids. They have different solubilities so they travel different distances up the paper.

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11
Q

Molecule

A

Group of atoms chemically bonded together

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12
Q

Signs of a chemical reaction (5)

A
  • colour change
  • effervescence, fizzing or bubbling
  • change in mass
  • change in temperature
  • formation of a precipitate
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13
Q

How does the total relative mass of reactants compare to the products

A

They are equal

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14
Q

Percentage yield formula

A

Actual mass
— ——————- X 100
Theoretical mass

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15
Q

Steps for finding reacting mass

A
  1. Find the Mr of the element/compound reactant and product
  2. Add units (g) to this number
  3. Make the reactant mass into 1g by dividing both numbers by the reactant mass
  4. Multiply the numbers by the mass of the reactant in the question
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16
Q

Avagrado’s constant

A

6.02 x 10 to the power of 23

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17
Q

Mole

A

An amount of substance that contains the same number of atoms present in 12 g of carbon 12

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18
Q

Number of moles =

A

Mass
— ——
Molar mass

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19
Q

Units for mole

A

g/mol

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20
Q

charge of a proton

A

+1

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21
Q

charge of a neutron

A

0

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22
Q

charge of an electron

A

-1

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23
Q

charge of an atom

A

neutral

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24
Q

mass number

A

number of protons and neutrons in the nucleus

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25
Q

atomic number

A

number of protons in the nucleus (and electrons in electron shells)

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26
Q

characteristics of group 1 metals (6)

A
  • conductors
  • soft
  • low - melting point
  • low density
  • stored in oil
  • shiny when freshly cut
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27
Q

characteristics of group 7 halogens (5)

A
  • toxic
  • non conductive
  • low melting/boiling point
  • brittle if solid
  • become darker in colour as you descend the group
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28
Q

what do alkali metals react with water to form

A

react vigorously with water to form metal hydroxide + hydrogen

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29
Q

what do alkali metals react with air to form

A

metal oxide

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30
Q

what do halogens react with metal to form

A

metal halides

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31
Q

how is reactivity affected as you move down group 1

A

it increases

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32
Q

how is reactivity affected as you move down group 7

A

it decreases

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33
Q

how are melting/boiling points affected as you descend group 1

A

they decrease

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34
Q

how are melting/boiling points affected as you descend group 7

A

they increase ( at room temp chlorine is a gas, bromine is a liquid and iodine is a solid)

35
Q

Which are more reactive group 1 or 2 elements and why

A

Group 1 as losing 1 electron is easier than losing 2

36
Q

Which are more reactive group 6 or 7 elements and why

A

Group 7 elements as gaining 1 more electron is easier than gaining 2

37
Q

Explain the reactivity of elements as you descend group 1

A

As you descend group 1, reactivity increases. All of the elements have 1 electron in their outer shell and therefore need to lose one electron to have a full outer shell. As you move down the group distance between the nucleus and outer shell increases, decreasing force of attraction. This makes it easier to lose an electron. Lithium finds it difficult to lose an electron while potassium finds it easier.

38
Q

Explain the reactivity of elements as you descend group 7

A

As you descend group 7, reactivity decreases. All of the elements have 7 electrons in their outer shell and therefore need to gain an electron to have a full outer shell. As you descend the group distance between the nucleus and outer shell increases, decreasing the force of attraction. Therefore, it becomes more difficult to gain an electron as you descend the group. Fluorine gains electrons easily while bromine finds it more difficult to gain electrons.

39
Q

Observations of reactions of alkali metals with oxygen

A

Tarnishing of freshly cut surface. They tarnish quicker if they are more reactive.

40
Q

What pH are metal hydroxides

A

Alkaline

41
Q

What colour does lithium burn in combustion reaction with oxygen

A

Burns with crimson/red flame

42
Q

What colour does sodium burn in a combustion reaction with oxygen

A

Yellow/orange flame

43
Q

What colour does potassium burn in a combustion reaction with oxygen

A

Lilac flame

44
Q

Word equation for reaction of alkali metal with oxygen

A

Alkaline metal + oxygen —-> metal oxide

45
Q

Symbol equation for reaction of lithium with oxygen

A

4Li + 02 —> 2Li2O

46
Q

Observations of lithium reaction with water

A

moves slowly around the surface of the water, fizzes (effervescence)

47
Q

Observations of sodium reaction with water

A

fizzes and forms a molten ball that moves quicker on the waters surface

48
Q

Observations of potassium reaction with water

A

lilac flame and moves very quickly on the waters surface, forms a molten ball

49
Q

Symbol equation for reaction of lithium with water

A

2Li + 2H2O —-> 2LiOH + H2

50
Q

Word equation for reaction of alkali metal and halogen

A

Alkali metal + halogen —-> Alkali metal halide

51
Q

Word equation for potassium reaction with chlorine

A

Potassium + chlorine —> potassium chloride

52
Q

Symbol equation for reaction of lithium with bromine

A

2Li + Br2 —> 2LiBr

53
Q

What do all alkali metal halides look like

A

White solids

54
Q

Test used to identify hydrogen gas

A

Gather gas into test tube. Hold a little splint in the test tube. If hydrogen gas is present a squeaky pop is observed

55
Q

Colour of bromine at room temp

A

Brown/red

56
Q

Colour of iodine at room temp

A

Blue/black

57
Q

Colour of chlorine at room temp

A

Pale, yellow/green

58
Q

Word equation for reaction of halogen with iron

A

Iron + halogen —-> iron(III) halide (salt)

59
Q

Iron + chlorine

A

2Fe + 3Cl2 —> 2FeCl3

60
Q

Why are displacement reactions of halogens better evidence than reactions with iron for reactivity

A

The halogens different states at room temp make it difficult to compare reactivities based on observation

61
Q

What colour are halide solutions

A

Colourless

62
Q

What colour does the solution turn if chlorine displaces bromine

A

Orange/brown

63
Q

Word equation for sodium bromide + chlorine

A

Sodium bromide + chlorine —> sodium chloride + bromine (s)

64
Q

What colour does does the solution turn when bromine displaces iodine

A

Red-brown

65
Q

Symbol equation for sodium iodide + bromine

A

2NaI + Br2 —> 2NaBr + I2

66
Q

Properties of chlorine/iodine

A

Toxic/poisonous, kill bacteria

67
Q

A Use of chlorine

A

Treatment of water supplies

68
Q

Use of iodine

A

Used as antiseptic following hospital procedures

69
Q

What colour is a calcium flame

A

Brick red

70
Q

What colour is barium flame

A

Apple green

71
Q

What colour does sodium chloride turn with silver nitrate

A

White

72
Q

What colour does sodium bromide turn with silver nitrate

A

Cream

73
Q

What colour does sodium iodide turn with silver nitrate

A

Yellow

74
Q

Word equation for sodium chloride + silver nitrate

A

Sodium chloride + silver nitrate —> sodium nitrate + silver chloride

75
Q

Symbol equations for silver nitrate + sodium bromide

A

AgNO3(aq) + NaBr(aq) —> NaNO3(aq) + AgBr(s)

76
Q

Ionic equation for silver nitrate + sodium iodide

A

Ag+(aq) + I-(aq) —> AgI(s)

77
Q

Properties of helium

A

Very low density, unreactive

78
Q

Properties of neon

A

Emits light when electric current is passed through it

79
Q

Argon

A

Unreactive

80
Q

Use of helium

A

Used in airships

81
Q

Use of neon

A

Used in advertising signs

82
Q

Use of argon

A

An an inert atmosphere for welding or in light bulbs

83
Q

what can be observed in the reaction between iron wool and chlorine gas

A

it glows brightly

GCSE Chemistry (6 decks)

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