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Combined Science GCSE > Chemistry: Key Concepts > Flashcards

Chemistry: Key Concepts Flashcards

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1
Q

Magnesium + oxygen > ?

A

Magnesium oxide

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2
Q

2Mg + O(little2) > ?

A

2MgO

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3
Q

Balance: Fe + Cl(little2) > FeCl(little3)

A

2Fe + 3Cl(little2) > 2FeCl(little3)

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4
Q

Hydrogen and Oxygen molecules are formed in a reaction where water splits apart. State the word and symbol equation.

A

Water > hydrogen + oxygen

2H(little2)O > 2H(little2)+O(little2)

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5
Q

What’s the state symbol for solid?

A

s

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6
Q

What’s the state symbol for liquid?

A

l

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7
Q

What’s the state symbol for gas?

A

g

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8
Q

What’s the state symbol for aqueous?

A

aq

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9
Q

What does aqueous mean?

A

Dissolved in water

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10
Q

What is the chemical formula of water?

A

H(little2)O

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11
Q

What is the chemical formula of ammonia?

A

NH(little3)

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12
Q

What is the chemical formula of hydrogen?

A

H(little2)

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13
Q

What is the chemical formula of carbon dioxide?

A

CO(little2)

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14
Q

What is the chemical formula of chlorine?

A

Cl(little2)

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15
Q

What is the chemical formula of oxygen?

A

O(little2)

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16
Q

What is the formula of Ammonium?

A

NH(little4)^+

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17
Q

What is the formula of hydroxide?

A

OH^-

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18
Q

What is the formula of nitrate?

A

NO(little3)^-

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19
Q

What is the formula of carbonate?

A

CO(little3)^2-

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20
Q

What is the formula of Sulfate?

A

SO(little4)^2-

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21
Q

When do ions form?

A

When atoms or groups of atoms gain or lose electrons to form charged particles

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22
Q

What is in an ionic equation?

A

Reacting particles and the products they form

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23
Q

How do you write an ionic equation?

A

Balance the symbol equation, then take out any aqueous ions present on both sides of the equation

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24
Q

Write the ionic equation for the following reaction: CaCl(little2)(aq) + 2NaOH(aq) > Ca(OH)(little2)(S) + 2NaCl(aq)

A

1: write out equation showing all aqueous ions separately
Ca^2+ (aq) + 2Cl^-(aq) + 2Na^+(aq)+2OH^-(aq)>Ca(OH)(little2)(S)+2Na^+(aq)+2Cl^-(aq)

2: To get to ionic equation, cross out anything that’s the same on both sides of the equation
Ca^2+(aq)+2OH^-(aq)>Ca(OH)(little2)(S)

(Overall charge should be the same on both sides)

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25
Q

Ca^2+(aq)+2OH^-(aq)>Ca(OH)(little2)(S)

Work out charge on left hand side

A

(2+)+(2x1-)=0

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26
Q

Write the ionic equation for the following reaction: HNO(little3)+NaOH(aq)>NaNO(little3)(aq)+H(little2)O(l)

A

H^+(aq)+OH^-(aq)>H(little2)O(l)

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27
Q

What does the hazard symbol showing an O with a flame on mean?

A

Oxidising: provides oxygen which allows other materials to burn more fiercely

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28
Q

What does the hazard symbol showing a fish and tree mean?

A

Environmental hazard: harmful to organisms and to the environment

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29
Q

What does the hazard symbol showing skull and crossbones mean?

A

Toxic: can cause death

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30
Q

What does the hazard symbol showing an exclamation point mean?

A

Harmful: can cause irritation, reddening or blistering of the skin

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31
Q

What does the hazard symbol showing a fire mean?

A

Highly flammable: catches fire easily

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32
Q

What does the hazard symbol showing test tubes a bench and a hand mean?

A

Corrosive:destroys materials including living tissue

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33
Q

What three things do you need to consider in a risk assessment?

A

Work out how likely it is that something would go wrong, how serious it would be if it did go wrong, then how to reduce this risk

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34
Q

A student is carrying out an experiment using two chemicals. Chemical A is corrosive and chemical B is highly flammable. Suggest appropriate safety precautions the student could take to minimise the risks associated with these chemicals.

A

The student should wear goggles, gloves and a lab coat while handling chemical A, and should also use low concentrations of chemical A. When handling chemical B, student should take care to keep it away from naked flames.

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35
Q

Who described the atom structure as a solid sphere? When?

A

John Dalton, 19th century

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36
Q

Describe the solid sphere model

A

Different solid spheres made up different elements. An atom was completely solid.

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37
Q

Who and when came up with the ‘plum pudding’ atom model? How did he prove previous model wrong?

A

1897, J J Thomson concluded atoms weren’t solid spheres because his measurements or charge and mass showed atom must contain smaller, negatively charged particles (electrons)

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38
Q

Describe a plum pudding model

A

A positively charged sphere with small negatively charged electrons inside

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39
Q

Who and when came up with the nuclear atom model? How did he prove previous model wrong?

A

1909, Ernest Rutherford. Famous gold foil experiment: positively charged alpha particles fired at thin sheet of gold.

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40
Q

During the famous gold foil experiment, what did they expect to see happen?

A

Expecting particles to pass straight through sheet or be slightly deflected, because positive charge of each atom was very spread out through solid ‘pudding’ of atom

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41
Q

During the famous gold foil experiment, what actually happened?

A

Most particles went straight through, some were deflected more than expected, small number were deflected backward

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42
Q

Describe the theory of the nuclear atom

A

Tiny tiny positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons. Most of the atoms is empty space.

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43
Q

Who came up with the Bohr model? How did he prove previous model wrong?

A

Niels Bohr. Electrons in a cloud around nucleus would be attracted to nucleus, causing atom to collapse.

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44
Q

Describe the Refined Bohr Model

A

Electrons were contained in shells, exist in fixed orbits, shells have a fixed energy.

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45
Q

How do scientists validate/propose a theory?

A

Back it up by evidence. Fit them to evidence and put research up for peer review.

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46
Q

Describe the gold foil experiment and how it disproves the plum pudding model of the atom.

A

During gold foil experiment, alpha particles were fired at a thin sheet of gold. Plum pudding model predicted alpha particles would pass through sheet/be slightly deflected. Most particles DID pass through, but a few were deflected more than expected, some bounced right back. This suggested atom was Mostly empty space, with positive nucleus in the centre.

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47
Q

Draw and label a diagram to show the Bohr model of an atom

A

Nucleus in the middle, shells with electrons on them

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48
Q

What do atoms make up?

A

All subtances

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49
Q

What are the three things an atom contains?

A

Protons neutrons and electrons

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50
Q

What is relative mass?

A

Measured mass on a scale where the mass of a proton or neutron is 1

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51
Q

What is relative mass measured in?

A

Atomic mass units

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52
Q

Relative mass of a proton?

A

1

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53
Q

Relative mass of a neutron?

A

0.0005

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54
Q

Relative charge of a proton?

A

+1

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55
Q

Relative charge of a neutron?

A

0

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56
Q

Relative charge of a electron?

A

-1

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57
Q

What are protons neutrons and electrons classified as?

A

Subatomic particles

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58
Q

Describe a proton

A

Heavy and positively charged

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59
Q

Describe a neutron

A

Heavy and neutral

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60
Q

Describe an electron

A

Has hardly any mass and is negatively charged

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61
Q

Where in the atom is the nucleus?

A

Middle of atom

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62
Q

What does nucleus of atom contain?

A

Protons and neutrons

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63
Q

What charge does a nucleus have? Why?

A

Positive due to the protons

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64
Q

Where is the mass of the atom?

A

Concentrated in the nucleus

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65
Q

How big is nucleus compared to whole atom?

A

Tiny

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66
Q

How do electrons move in the atom?

A

Around the nucleus In electron shells

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67
Q

How are electrons charged?

A

Negatively charged

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68
Q

What are the size of electrons in an atom?

A

Tiny, but shells cover lots of space

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69
Q

What determines the size of the atom?

A

The size of electron shells

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70
Q

What is the atomic radius of a atom?

A

About 10^-10m

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71
Q

What can we say about the number of protons and electrons in an atom?

A

They are the same

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72
Q

What is the overall charge of an atom? Why?

A

Neutral, because it has the same number of protons and electrons

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73
Q

What is an ion?

A

An atom or group of atoms that has gained or lost electrons

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74
Q

Why do electrons and protons cancel each other out in an atom?

A

Charge of electrons is same size as charge of protons, so they cancel each other out

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75
Q

If an ion has a 2- charge, what can we say about number of electrons in relation to number of protons?

A

Two more electrons than protons

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76
Q

What does the atomic number tell us?

A

How many protons an atom has

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77
Q

Can the proton number of an element change?

A

Nope

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78
Q

What does the mass number tell us?

A

Total number of protons + neutrons

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79
Q

Where in the nuclear symbol for an atom is the mass number?

A

On top

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80
Q

Where in the nuclear symbol for an atom is the atomic number?

A

Bottom

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81
Q

How do you work out the number of neutrons in an atom?

A

Subtract atomic number from mass number

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82
Q

A certain neutral atom of potassium has an atomic number of 19 ad a mass number of 39 give the number of electrons, protons and neutrons in the atom

A 
Electrons = 19
Protons = 19
Neutrons = 39-19=20
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83
Q

Why is an isotope

A

A different form of an element, with the same number of protons as original, but different number of neutrons (same atomic number, different mass number)

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84
Q

In a nucleus symbol on the periodic table, which number is the relative atomic mass number?

A

The larger number

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85
Q

What is relative atomic mass of an element?

A

The average mass of one atom of an element (compared to 1/12 of the mass of one atom of carbon-12)

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86
Q

If an element only has 1 isotope, it’s relative atomic mass will be the same as what?

A

It’s mass number

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87
Q

What letters are relative atomic mass represented by?

A

Ar

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88
Q

If an element only has more than one isotope, it’s relative atomic mass is what?

A

The average of the mass numbers of all the different isotopes, taking into account how much there is of each one

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89
Q

What does isotopic abundances mean?

A

Different isotopes of an element occurring in different quantities

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90
Q

How do you work out the relative atomic mass of an element?

A

Find the average mass of all its atoms

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91
Q

How do you find the average mass of all the atoms of an element?

A

Multiply each relative isotopic mass by its relative abundance, and add up the results. Divide by the sum of the isotopic abundances (if abundances are given as percentages, this will be 100)

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92
Q

Boron has two isotopes, boron-10 and boron-11. Given that the relative abundances of boron-10 and boron-11 are 4 and 16 respectively, work out the relative atomic mass of boron

A

1)Multiply each relative isotopic mass by its relative abundance, and add up the results.
(10x4)+(11x16)=216
2) Divide by the sum of the isotopic abundances
216 divided by (16+4)=10.8

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93
Q

The isotope boron-11.. what is the relative isotopic mass?

A

11

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94
Q

Bromine has an atomic number of 35 and has two stable isotopes: bromine-79 and bromine-81. Given that 51% of bromine atoms are bromine-79, and 49% are bromine-81, work out the relative atomic mass of bromine. Give your answer to the nearest whole number.

A

(79x51)+(81x49)=7998

7998/100=79.98=80

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95
Q

How did early chemists try to find out more about elements?

A

By looking at patterns in the elements properties

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96
Q

Who made the first proper periodic table? When?

A

Dmitri Mendeleev, 1869

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97
Q

How did Dmitri Mendeleev order his table?

A

Elements with similar chemical properties in columns, in order of atomic mass, with gaps left where an element was missing

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98
Q

What helped confirm the idea of Dmitri Mendeleev’s table?

A

The fact he could correctly predict the properties of undiscovered elements using the other elements in that column

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99
Q

What are the first two left columns (from left) of the periodic table called?

A

Reactive metals

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100
Q

What is the third (from left) to ninth (from left) row of the periodic table called?

A

Transition metals

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101
Q

On the periodic table, what are the elements on the right of the transition metals under the ‘staircase line’ called?

A

Transition metals

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102
Q

On the periodic table, what does the ‘staircase line’ do?

A

Separates metals from non metals

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103
Q

Why is the far right column of the periodic table called?

A

Noble gases

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104
Q

What is the section of elements above the staircase line on the right side of the periodic table (excluding last column) called?

A

Non metals

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105
Q

What can you say about elements in the same column?

A

They have similar chemical properties

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106
Q

What can we say the group number which the element belongs to corresponds to?

A

To the number of electrons it has in it’s outer shell

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107
Q

How many electrons in its outer shell will a group 1 element have?

A

1

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108
Q

How many electrons in its outer shell will a group 7 element have?

A

7

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109
Q

How many electrons in its outer shell will a group 0 element have?

A

8

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110
Q

What are the rows (horizontal) in periodic tables called?

A

Periods

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111
Q

What can we say the period number which the element belongs to corresponds to?

A

The number of shells of electrons it has

112
Q

What are electron shells sometimes known as?

A

Energy levels

113
Q

How many electrons can go in the first shell of a atom? Second shell?

A

First=2

Second + = 8

114
Q

Give the electronic configuration of aluminium. Draw a diagram.

A

Diagram= nucleus, 3 shells, 3 electrons on outer shell
2.8.3
Atomic no.=13

115
Q

When do simple ions form?

A

When atoms gain or lose electrons

116
Q

What are ions?

A

A single atom or group of atoms that are Charged particles

117
Q

Why do atoms become ions?

A

Because they’re trying to get a full outer shell

118
Q

If an atom has a full outer shell, what is this called?

A

A stable electronic structure

119
Q

What is the name for negative ions?

A

Anions

120
Q

What is the name for positive ions?

A

Actions

121
Q

What is an anion?

A

Negative ion

122
Q

What is a cation?

A

Positive ion

123
Q

When do anions form?

A

When atoms gain electrons - they have more electrons than protons

124
Q

When do cations form?

A

When atoms lose electrons -they above more protons than electrons

125
Q

How can we say the charge of an ion relates to how many electrons it loses or gains?

A

They are the same

126
Q

If an atom loses 2 electrons, what is the charge of the ion?

A

2+

127
Q

If an atom gains 3 electrons, what is the charge of the ion?

A

3-

128
Q

How many electrons does the ion F^- have?

A

F- has a single negative charge, so it must have one more electrons than protons. F has an atomic number of 9, so has 9 protons. So F- must have 9+1=10 electrons

129
Q

How many electrons does the ion Fe^2+have?

A

Has a 2+ charge, so it must have two more protons than electrons. Fe has an atomic number of 26, so has 26 protons, so Fe^2+ must have 26-2=24 electrons

130
Q

Which groups in the periodic table are most likely to form ions?

A

1 and 2 and 6 and 7

131
Q

What charge of ions will group 1 elements form?

A

1+

132
Q

What charge of ions will group 2 elements form?

A

2+

133
Q

What charge of ions will group 6 elements form?

A

2-

134
Q

What charge of ions will group 7 elements form?

A

1-

135
Q

What are ionic compounds made of?

A

A positively charged part and a negatively charged part

136
Q

What is the overall charge of any ionic compound? What does this mean?

A

Zero. All negative charges in the compound must balance all the positive charges

137
Q

What can we say about ions ending in -ate (e.g. Nitrate)

A

They’re negative ions containing oxygen and at least one other element

138
Q

What can we say about ions ending in -ide (e.g. Chloride), and what is the one exception to this rule

A

They’re negative ions containing only one element (apart from hydroxide ions which are OH-)

139
Q

Work out the chemical formula of calcium nitrate

A

1) write out the formulas of the calcium nitrate ions
Ca^2+, NO(little3)^-
2) the overall charge must be zero, so work out ratio of Ca:NO(little3) that gives an overall neutral charge
To balance 2+ charge on Ca^2+, you need two NO(little3)^- ions: (+2)+(2x-1)=0
The formula is Ca(NO(little3))(little2)

140
Q

Ca(NO(little3))(little2)

What do the brackets show you?

A

You need two of the whole nitrate ion

141
Q

In chemistry, what are the three types of bonding?

A

Ionic, covenant and metallic

142
Q

What is ionic bonding?

A

When a metal an non metal react together, the metal atom loses electrons to form a cation, and non metal gains these electrons to form an anion. These oppositely charged ions are strongly attracted to each other by electrostatic forces, this attraction is called an ionic bond

143
Q

What is the phrase that describes ionic bonding

A

Transfer of electrons

144
Q

What are dot and cross diagrams used for?

A

To show how ionic compounds are formed

145
Q

What is a dot and cross diagram? What does it do?

A

They show the arrangement of electrons in an atom or ion. Each electron is represented by a dot or cross, so they can show which atom the electrons in an ion originally came from

146
Q

Draw a dot and cross diagram for sodium chloride (NaCl)

A

(Check page 84 for answer)
The sodium atom gives up its outer electron, becoming an Na^+ ion. The chlorine atom picks up the electron, becoming a Cl^- (chloride) ion

147
Q

Draw a dot and cross diagram for Magnesium Oxide (MgO)

A

(Check page 84 for answer)
The magnesium atom gives up its two outer electrons, becoming an Mg^2+ ion. The oxygen atom picks up the electrons, becoming an O^2- (Oxide) ion

148
Q

Draw a dot and cross diagram for magnesium chloride (MgCl(little2))

A

The magnesium atom gives up its two outer electrons, becoming an Mg^2+ ion. The two chlorine atoms pick up one electron each, becoming two Cl^- (chloride) ions

149
Q

Draw a dot and cross diagram for sodium oxide (Na(little2)O)

A

Two sodium atoms each give up there single outer electron, becoming two Na^+ ions. The oxygen atom picks up the two electrons, becoming an O^2- ion

150
Q

Describe, in terms of electronic transfer, how sodium (Na) and chlorine (Cl) react to form sodium chlorine (NaCl)

A

Each sodium atom loses an electron to form an Na^+ ion. Each chlorine atom gains an electron to form a Cl^- ion. The oppositely charged ions are attracted to each other by electrostatic attraction.

151
Q

How can we describe the structure of an ionic compound?

A

They have a regular lattice structure

152
Q

Describe the structure of ionic compounds, in detail

A

Ionic compounds have giant ionic lattice structures. Ions form closely packed regular lattice. There are strong electrostatic forces of attraction between oppositely charged ions in all directions

153
Q

What can we say about the properties of ionic compounds?

A

They all have similar properties

154
Q

What is the melting/boiling point of ionic compounds?

A

High

155
Q

Why do ionic compounds have a high melting and boiling point?

A

Due to strong attractions between ions. It takes a large amount of energy to overcome this attraction.

156
Q

Can solid ionic compounds conduct electricity? Why?

A

No, ions are fixed in place and can’t move

157
Q

Can melted ionic compounds conduct electricity? Why?

A

Yes, ions are free to move so can carry an electric current

158
Q

Can or can’t most ionic compounds dissolve easily in water?

A

Can

159
Q

If an ionic compound is dissolved in water, can or can’t it conduct electricity? Why?

A

The ions have separated and are free to move in the solution, so they’ll carry an electric current

160
Q

What are the three types of models that show ionic structure?

A

2D representations, Dot and Cross diagrams, 3D models

161
Q

How does 2D representation model show ionic structure? Give two drawbacks of this model.

A

Displayed formulas of molecules show what atoms something contains, and how atoms are connected.

1: don’t show shape of substance
2: don’t give any idea about sizes of the atoms

162
Q

How does dot and cross diagrams model show ionic structure? Give two drawbacks of this model.

A

Show how compounds or molecules are formed and where electrons in the bonds or ions came from.

1: don’t usually show anything about size of the atom or ions
2: don’t show how atoms or ions are arranged

163
Q

How does 3D models show ionic structure? Give a drawbacks of this model.

A

Models of ionic sold is show arrangement of ions

1: they can only show the outer layer of a substance

164
Q

What are the three ways of creating a ball and stick model to show ionic compounds?

A

Draw them, make with plastic molecular model kits, or as computer models

165
Q

What is 2 positive and 2 negatives of ball and stick models to show ionic compounds structure?

A

Help visualise structures
More realistic than 2D drawings

Misleading- make it look like there are large gaps between atoms
Don’t show correct scales of atoms or ions

166
Q

What is a covelant bond?

A

A strong bond that forms when a pair of electrons is shared between two atoms

167
Q

What structure do substances containing covalent bonds usually have?

A

Simple molecular substances

168
Q

Draw a dot and cross diagram showing covalent bonding in hydrogen

A

Check page 86

169
Q

Draw a dot and cross diagram showing covalent bonding in hydrogen chloride

A

Page 86

170
Q

Draw a dot and cross diagram showing covalent bonding in water

A

Page 86

171
Q

Draw a dot and cross diagram showing covalent bonding in oxygen

A

Page 86

172
Q

Draw a dot and cross diagram showing covalent bonding in methane

A

Page 86

173
Q

Draw a dot and cross diagram showing covalent bonding in carbon dioxide

A

Page 86

174
Q

What is the chemical formula for hydrogen?

A

H(little2)

175
Q

What is the chemical formula for hydrogen chloride?

A

HCl

176
Q

What is the chemical formula for water?

A

H(little2)O

177
Q

What is the chemical formula for oxygen?

A

O(little2)

178
Q

What is the chemical formula for carbon dioxide?

A

CO(little2)

179
Q

What is the chemical formula for methane?

A

CH(little4)

180
Q

In a stick and ball model (to show ionic compound structure)there is a space left between atoms/ions, what does this space represent?

A

The space where electron clouds interact

181
Q

What is the general size of simple molecules? What is the general size of bonds between these molecules

A

10^-10m (Small af)and 10^-10m

182
Q

What can we say about strength of covelant bonds and forces of attraction between molecules?

A

Covalent bond = strong

Forces of attraction between molecules = very weak

183
Q

What can we say about the melting/boiling point of simple molecular compounds? (High or low) Why?

A

Low boiling point, because only need to break feeble intermolecular forces, not covalent bonds. Molecules easily parted

184
Q

What can we say about most molecular substances at room temperature ?

A

They’re gases or liquids

185
Q

What can we say about molecule size, strength of intermolecular forces and melting and boiling points, in relation to each other?

A

Bigger molecules > increased strength of molecular forces > melting and boiling point Increase

186
Q

Do molecular compounds conduct electricity? Why?

A

No, they don’t contain any free electrons or ions

187
Q

What can we say about simple molecular solubility in water?

A

Some are soluble and some aren’t

188
Q

What are polymers?

A

Polymere are molecules made up of long chains of covalently bonded carbon atoms

189
Q

When are polymere formed?

A

When lots of small molecules called monomers join together

190
Q

What are the four properties most giant covalant structures have?

A

All atoms are bonded to each other by strong covalent bonds
Very high melting and boiling points as lots of energy is needed to break covalent bonds
Don’t contain charged particles, don’t conduct electricity (except graphite + graphene)
Aren’t soluble in water

191
Q

What are the three main examples of carbon based giant covalent structures?

A

Diamond, graphite and graphene

192
Q

Explain the structure of diamond

A

Diamond is mad up of a network of carbon atoms that each form four covenant bonds

193
Q

Why is diamond so hard?

A

Because the strong covalent bonds hold the atoms in a rigid lattice structure

194
Q

Does diamond conduct electricity? Why?

A

No, it has no free electrons or ions

195
Q

Describe the structure of graphite, and how this effects the material.

A

Each carbon atom only forms three covalent bonds, creating sheets of carbon atoms arranged in hexagons. No covalent bonds between layers, so they’re free to move over each other, making graphite soft and slippery

196
Q

Due to graphites nature, what is it ideal to be used as?

A

A lubricating material

197
Q

Is the melting point of graphite high or low? Why?

A

High, covalent bonds in the layers need lots of energy to break

198
Q

Can graphite conduct electricity? Why?

A

Yes, because only one out of each carbons four outer electrons are used in bonds, so each carbon atom has one electron that’s delocalised (free) and can move

199
Q

Describe the structure of Graphen es

A

Graphen is a type of fullerene, and is one layer of graphite. It’s a sheet of carbon atoms joined together hexagons. The sheet is just on atom thick, making it a 2D compound.

200
Q

What are fullerenes?

A

Fullerenes are are molecules of carbon, shaped like closed tubes or hollow balls

201
Q

Describe the general structure of fullerenes

A

Mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons (rings of five carbons) or heptagons (rings of seven carbons)

202
Q

What can fullerenes be used for? How? How could this be practically applied in the world?

A

To ‘cage’ other molecules, fullerenes structure forms around another atom in a molecule, which is trapped inside, could be used to deliver a drug directly to cells in body

203
Q

What could fullerenes be used to make and why?

A

They have a huge surface area so can be used to make industrial catalysts, as individual catalyst molecules could be attached to the fullerenes

204
Q

Give three examples of fullerenes

A

Graphene, nanotubes, buckminsterfullerene

205
Q

Describe what buckminsterfullerene is? (Molecular formula, structure, type of molecule/what it forms)

A

Fullerenes that Has the molecular formula C(little60) and forms a hollow sphere made of 20 hexagons and 12 pentagons. It’s a stable molecule that forms soft brownish-black crystals

206
Q

Describe what nanotubes are? (Structure, electricity conduct?, what can be used for and why, practical application)

A

Fullerenes that are like tiny cylinders of graphene. They conduct electricity. High tensile strength (don’t break when stretched) so can strengthen materials without adding weight. Could strengthen sports equipment that needs to be strong while being lightweight.

207
Q

What does metallic bonding involve?

A

Delocalised electrons

208
Q

What structure do metals consist of?

A

Giant structure

209
Q

Describe the structure of a metal atom

A

Giant structure, electrons in outer shell are delocalised

210
Q

What is metallic bonding?

A

strong forces of electrostatic attraction between the positive metal ions and shared (between ions) negative electrons. These forces of attraction hold atoms together in a regular structure.

211
Q

How strong is metallic bonding?

A

Very strong

212
Q

What compounds are held together by metallic bonding?

A

Metallic elements and alloys

213
Q

What in a metallic bond produces all the properties of metals?

A

The delocalised electrons

214
Q

What is the melting boiling point of metals? Why? What does this mean for the properties of the compound in room temperature?

A

High melting boiling point, because electrostatic forces between the metal ions and the delocalised sea of electrons are very strong so need lots of energy to be broken . They’re generally shiny solids at room temperature

215
Q

Are metals soluble in water?

A

Nope

216
Q

What can we say about the general density of metals compared to non metals, and why is this?

A

Metals are denser than non metals as the ions in metallic structure are packed close together

217
Q

Why are pure metals malleable? What does malleable mean?

A

The layers of atoms in a pure metal can slide over each other, making metals malleable - this means they can be hammered or rolled into flat sheets

218
Q

Can metals conduct electricity /heat? Why?

A

Yes’m be shed delocalised electrons carry electrical current and thermal energy through the material

219
Q

Do all metals have metallic bonding?

A

Yep

220
Q

Why do metals and non metals have different properties?

A

Metals = metallic bonding

non metals = no metallic no metallic bonding

221
Q

What can we say about metals and non metals in terms of gaining and loosing electrons

A

Non metals = gain electrons

Metals = loose electrons

222
Q

Where do metals and non metals tend to be on the periodic table?

A

Non Metals = top (H) and right hand side

Metals = bottom (transition metals) and left hand side

223
Q

What can we say about conservation of mass in a chemical reaction?

A

Mass is always conserved

224
Q

What is conservation of mass? What does this mean?

A

When no atoms are destroyed and no atoms are created, meaning there are same number and types of atoms on both sides of reaction equation

225
Q

Give an example and explain an experiment used to show conservation of mass in a closed system

A

Precipitation reaction: two solutions react and an insoluble solid, called a precipitate, forms in the solution

226
Q

A mass appears to increase in a chemical reaction, in an unsealed reaction vessel. Why?

A

At least one reactant is a gas found in air, and products are solids, liquids or aqueous. Gas becomes part of product, total mass of stuff inside the reaction vessel increases.

227
Q

Give an example of mass seeming to increase in a chemical reaction, in an unsealed reaction vessel

A

Metal in an unsealed container reacts with oxygen from air, so mass inside container increases. Mass of metal oxide produced equals total mass of the metal and the oxygen that reacted from air,

Metal (S) + oxygen (g) > metal oxide (s)

228
Q

A mass appears to decrease in a chemical reaction, in an unsealed reaction vessel. Why?

A

Some or all of reactants are solids, liquids or aqueous and at least one product is gas. Before reaction, solid liquid or aqueous are in vessel. As it turns to gas, gas escapes.

229
Q

Give an example of mass seeming to decrease in a chemical reaction, in an unsealed reaction vessel

A

Metal carbonate thermally decomposes in an unsealed container to form a metal oxide and carbon dioxide ga, the mass of the container will appear to decrease as carbon dioxide escapes. In reality, mass of the metal oxide and carbon dioxide produced will equal mass of metal carbonate that reacted

Metal carbonate (S) > metal oxide (s) + carbon dioxide (g)

230
Q

What is relative formula mass represented by?

A

Mr

231
Q

What is relative formula mass?

A

The relative atomic masses of all the atoms in its formula added together

232
Q

Find relative formula mass of magnesium chloride MgCl(little 2)

A

Use periodic table to find relative atomic masses of magnesium and chlorine. Add up relative atomic masses of all atoms in the formula to beg the relative formula mass

Ar(Mg) = 24
Ar(Cl) = 35.5
Mr(MgCl(little2)) = 24+(2x35.5)
= 24+71=95
Mr of MgCl(little2) = 95
233
Q

Find the relative formula mass of calcium hydroxide. Ca(OH)(little2)

A 
Ar(Ca)=40
Ar(O)=16
Ar(H)=1
Mr(Ca(OH)(little2)) = 40 + [(16+1)x2]
=40+34=74
Mr of Ca(OH(little2)) = 74
234
Q

What can we say the Mr of a compound is equal to?

A

To the mass in grams of 1 mole of the compound

235
Q

Wat does the empirical formula of a compound tell you?

A

The smallest whole number ratio of atoms in the compound

236
Q

Find the empirical formula of glucose, C(little6) H(little12) O(little6)

A

Numbers in the molecular formula of glucose are 6,12 and 6
To simplify ratio, divide them by the largest number that goes into 6,12 and 6: 6
C: 6/6=1
H:12/6=2
O:6/6=1
Empirical formula of glucose is CH(little2)O

237
Q

What can you use empirical formula of a compound with Relative formula mass to find?

A

It’s molecular formula

238
Q

Compound X has the empirical formula C(little2)H(little6)N. the Mr of compound X is 88. Find the molecular formula of compound X

A

Start by finding the Mr of the empirical formula. The Ar of carbon is 12, the Ar of Hydrogen is 1 and the Ar of nitrogen is 14.
Divide the Mr of the compound by the Mr of the empirical formula.
To get molecular formula, multiply everything in the empirical formula by the result (here, 2)

Mr(C(little2)H(little6)N) = (2xAr(C))+(6xAr(H))+Ar(N)
=(2x12)+(6x1)+14
=24+6+14=44

88/44=2

C: 2x2=4
H:6x2=12
N:1x2=2
Molecular formula of impound X is C(little4)H(little12)N(little2)

239
Q

What is the Mole? What is it equal to?

A

An amount of particles, equal to a number called Avogadro’s constant. It’s 6.02x10^23

240
Q

What can we say about Avogadro’s constant in predation to weight?

A

When you get that number (6.02x10^23) of atoms or molecules, of any element or compound, they weigh exactly the same number of grams as re relative atomic mass Ar (or relative formula mass Mr) of the element or compound

241
Q

One mole of atoms or molecules of any substance will have a mass in grams equal to what?

A

the relative particle mass (Ar or Mr) for that substance

242
Q

How much will one mole of carbon weigh?

A

Carbon has Ar of 12 so one mole weighs exactly 12g

243
Q

How much will one mole of nitrogen gas weigh?

A 
Nitrogen gas (N(little2)) has an Mr of 28 (2x14)
One mole of nitrogen gas weighs exactly 28g
244
Q

How much will one mole of hexane (C(little6)H(little14)) weigh?

A

Mr of 86 ((6x12)+(14x1))

So one mole of hexane weighs exactly 86g

245
Q

One mole of carbon weighs 12g
One mole of nitrogen gas weighs 28g
One mole of hexane weighs 86g

What can you say about how many particles they contain?

A

All contain the same number of particles, one mole, 6.02x10^23 particles

246
Q

How many atoms are there in five moles of oxygen gas?

A

Multiply Avogadro’s constant by the number of moles you have to find the number of particles
There a few two atoms in the ach molecule of oxygen gas, so Multilpy your answer by 2

  1. 02x10^23 z5=3.01x10^24
  2. 01x10^24x2=6.02x10^24
247
Q

What is the equation for number of moles?

A

Number of moles = mass in g (of element or compound) / Mr (of compound) or Ar (of Element)

248
Q

How many Magnesium atoms are there in 60g of magnesium? Ar of Mg= 24

A

Convert mass into moles using the equation
Moles = mass / Ar
= 60/24=2.5 moles

Multiply the number of moles by Avogadro’s constant to find the number of atoms
6.02x10^23x2.5
=1.505 x 10^24

249
Q

You need to get from a number of particles to a number of moles. What do you do to do this?

A

Divide by 6.02x10^23

250
Q

How many moles are th re in 66g of carbon dioxide?

A

Mr of carbon dioxide is (CO(little2)) = 12 + (16x2) = 44

Moles = mass / Mr = 66/44 = 1.5 moles

251
Q

What mass of carbon is there in 4 moles of carbon dioxide?

A

Mass = moles x Ar(C)

= 4 x 12 = 48g

252
Q

What is concentration?

A

A measure of how crowded things are

253
Q

What can we say about how he amount of solute dissolved into a given volume in relation to concentration of the solution

A

More solute = more concentrated

254
Q

What is concentration measured in?

A

g dm ^-3

Grams per dm^3

255
Q

1 gram of stuff dissolved into 1 dm^3 of solution has a concentration of ?

A

1 g dm^-3

256
Q

1 dm^3 = ? Litre/s = ? Cm^3

A

1 litre, 1000cm ^3

257
Q

What’s the equation for finding concentration from the mass of a solute?

A

Concentration = mass of solute / volume of solution

258
Q

What is volume of a solution measured in?

A

dm^3

259
Q

What is mason solute measured in?

A

Grams

260
Q

25g of copper sulphate is dissolved in 500cm^3 of water. What’s the concentration in g dm^-3?

A

Make sure values are right units. Volume needs to be converted to dm^3”
1000cm^3 = 1dm^3, 500cm^3 = (500/1000)dm^3=0.5dm^3

Now substitute values into the formula
Concentration = 25/0.5=50g dm^-3

261
Q

What mass of sodium chloride is in 300cm^3 of solution with a concentration of 12g dm^-3

A 
Rearrange formula so mass is by itself
Mass = concentration x volume
Put the volume into the right units
300cm^3 = (300 / 1000) dm^3 = 0.30 dm^3
Substitute the values into the rearranged formula
Mass = 12 x 0.30 = 3.6g
262
Q

What can we use to work out empirical formulas of a compound?

A

The masses of the element it contains

263
Q

A sample of hydrocarbon contains 36g of carbon and 6g of hydrogen . Work out the empirical formula of the hydrocarbon.

A

Remember: moles = mass/Mr
Work out how many moles of each element you have
Work out the smallest whole number ratio between the moles of C ajd H atoms to get the empirical formula

Ar(C)= 12
Moles of C = 36/12=3moles
Ar(H)=1
Moles of H = 6/1 = 6 moles
Ratio C:H = 3:6 
Divide both by /smallest/ 3
Ratio C:H = 1:2
Empirical formula is CH(little 2)
264
Q

6 steps of an experiment that can be used to calculate empirical formula of a metal oxide

A

1) heat crucible until red hot. (Cleans it)
2) leave crucible to cool. Then weigh (along with lid)
3) add clean magnesium ribbon to crucible. Reweigh, with lid + ribbon
New reading - initial reading = mass of magnesium
4) heat crucible with magnesium. Put on lid, leave small gap so oxygen can enter.
5) heat strongly for around 10 mins, or until magnesium ribbon turns white
6) allow to cool. Reweigh crucible with lid + contents.
Mass of magnesium oxide = new reading - initial reading

265
Q

A student heats 1.08g of magnesium ribbon in a crucible so it completely reacts to form magnesium oxide. The total mass of magnesium oxide formed was 1.80g. Calculate empirical formula of magnesium oxide.

A

1) extra mass in magnesium oxide came from oxygen, work out mass of oxygen
Mass of O= 1.80-1.08=0.72g
2) work out the number of moles of magnesium and oxygen atoms involved in the reaction
Moles of Mg = 1.08 / 24 = 0.045 moles
Moles of O = 0.72 / 16 = 0.045moles
3) work out lowest whole number ratio between Mg and O by dividing moles of both by the smallest number
Mg = 0.045 / 0.045 = 1
O = 0.045 / 0.045 = 1
Ratio = 1:1
Empirical formula of magnesium oxide is MgO

266
Q

When do reactions stop? What do we call the other reactants?

A

When one reactant is used up. The others are ‘in excess’

267
Q

What’s the reactant that’s used up in a reaction called?

A

A limiting reactant

268
Q

What can we say about the limiting reactant in terms of the amount of product formed? What does this mean for the reaction?

A

They’re directly proportional. More limiting reactant means more reactant particles to take part in reaction, meaning more product particles are made (as long as other reactants are in excess)

269
Q

What can we use the limiting reactant to calculate?

A

The amount of product

270
Q

Give the 5 steps of the calculation used to calculate the mass of a product formed from a liming reactant, using a balanced chemical equation. What else can this method be used to calculate?

A

1) write out the balanced equation
2) work out relative formula mass (Mr) of reactant and product you’re interested in
3) find out how many moles there are of the substance you know the mass of
4) use balanced equation to work out how many moles there’ll be of the other substance (how many moles of product will be made by this many moles of reactant)
5) use number of moles to calculate mass

Can also be used to find out mass of a reactant needed to produce a known mass of a product

271
Q

What can be used to calculate the mass of a product formed from a liming reactant?

A

A balanced chemical equation

272
Q

Calculate the mass of aluminium oxide, Al(little2)O(little3) formed when 135g of aluminium is burned in air

A

1) write out the balanced equation
4Al + 3O(little 2) > 2Al(little2)O(little3)
2) calculate relative formula masses of the reactants and products you’re interested in
Al:27
Al(little2)O(little3): (2x27)+(3x16)=102
3) calculate the number of moles of aluminium in 135g
Moles = mass / Mr = 135/27= 5
4)look at the ratio of moles in the equation
4 moles of Al react to produce 2 moles of Al(little2)O(little3) - half the number of moles are produced. So 5 moles of Al will react to produce 2.5moles of Al(little2)O(little3)
5) calculate mass of 2.5 moles of aluminium oxide
Mass = moles x Mr = 2.5 x 102 = 255g

273
Q

Magnesium oxide, MgO, can be made by burning magnesium in air. What mass of magnesium is needed to make 100g of magnesium oxide?

A

1) Write our the balanced equation
2Mg + O(little2) > 2MgO
2) Work out the relative formula masses of the reactants and products you’re interested in
Mg: 24
MgO: 24 + 16 = 40
3) calculate the number of moles of magnesium oxide in 100g
Moles = mass / Mr = 100/40 = 2.5
4) Look at the ratio of moles in the equation
2 moles of MgO are made from 2 moles of Mg. So 2.5 moles of MgO will be formed from 2.5 moles of Mg
5) Calculate the mass of 2.5 moles of Mg
Mass = moles x Mr = 2.5 x 24 = 60g

274
Q

What can we use to work out a balanced symbol equation?

A

The masses of the reactants and products that took part in the reaction

275
Q

Give the four steps working out a balanced symbol equation using given masses and reactants of products that took part in the reaction

A

1) divide the mass of each substance by its relative formula mass to find the number of moles
2) divide the number of moles of each substance by the smallest number of moles in the reaction
3) if needed, multiply all the numbers by the same amount to make them all whole numbers
4) write the balanced symbol equation for the reaction by putting these numbers in front of the formulas

276
Q

Paula burns a metal, X, in oxygen. There is a single product, an oxide of the metal. Given that 25.4g of X burns in 3.2g of oxygen, write a balanced equation for this reaction. Ar of X = 63.5 and Mr of X Oxide = 143.0

A

1) Work out the mass of metal oxide produced. Because it’s the only product the mass of metal oxide produced must equal the total mass of its reactants.
25.4+3.2=28.6g of X oxide
2) Divide the mass of each substance by its Mr or Ar to calculate how many moles of each substance reacted or were produced
X: 25.4/63.5=0.40 mol
O(little2): 3.2/32.0 = 0.10mol
X oxide: 28.6/143.0 = 0.20mol
3) divide by the smallest number of moles, which is 0.10:
X: 0.40/0.10=4.0
O(little2): 0.10/0.10=1.0
X oxide: 0.20/0.10=2.0
4) the numbers are all whole numbers, so you can write out the balanced symbol equation straight away.
4X + O(little2) > 2(X oxide)
5) the oxide of X must have a chemical formula containing X and O atoms. In order for the equation to balance, each molecule of X oxide must contain one O atom and two X atoms. 4X + O(little2) > 2X(little2)O

277
Q

8.1g of zinc oxide (ZnO) were put in a crucible with 0.30g of carbon and heated until they reacted. Given that the balanced chemical equation for this reaction is: 2ZnO + C > CO(little2) + 2Zn, work out the limiting reactant in this reaction

A

1) Divide the mass of each substance by its Mr or Ar to find how many moles of earful substance were reacted
ZnO: 8.1/81 = 0.10 mol
C: 0.30/12 = 0.025 mol
2) divide by the smallest number of moles, which is 0.025
ZnO: 0.10/0.025=4.0
C: 0.025/0.025=1.0
3) compare the ratios between the moles of products with the balanced chemical equation
In the balanced equation, ZnO and C react in a ratio of 2:1. Using the masses, there is a 4:1 ratio of ZnO to C. So, ZnO is in excess, and C must be the limiting reaction.

Combined Science GCSE (8 decks)

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