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edexcel igcse chemistry > unit one: principles of chemistry > Flashcards

unit one: principles of chemistry Flashcards

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1
Q

what are the three states of matter

A

solid, liquid and gas

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2
Q

describe the structure and arrangement of molecules in a solid

A

the molecules are tightly packed
held in fixed positions by strong forces
the molecules can vibrate around their fixed positions
as the solid gets hotter the vibrations get bigger.

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3
Q

describe the structure and arrangement of molecules in a liquid

A 
the molecules are closely packed
do not have a regular structure
the forces between the molecules are strong 
molecules move randomly
molecules are close together
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4
Q

describe the structure and arrangement of molecules in a gas

A

molecules are widely spaced
in a continuous state of random motion.
the forces between molecules are small except during collisions

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5
Q

solid to liquid is

A

melting

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6
Q

liquid to gas is

A

boiling

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7
Q

gas to liquid is

A

condensing

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8
Q

liquid to solid is

A

freezing

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9
Q

solid to gas is

A

subliming

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10
Q

the substance that dissolves is called the

A

solute

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11
Q

the liquid a solute dissolves in is called the

A

solvent

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12
Q

a solute and a solvent forms a

A

solution

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13
Q

solubility is

A

the mass of solute which must dissolve in 100g of solvent at that temperature

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14
Q

what is a saturated solution

A

a solution that contains as much dissolved solid as possible at a paticular temperature

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15
Q

what do you plot against what to get a solubility curve

A

solubility against temperature

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16
Q

what are atoms made up of

A

sub atomic particles : neutrons, protons and electrons

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17
Q

what are molecules made up of

A

usually, two or more atoms covalently bonded together. however the noble gases exist as atoms at room temperature and pressure, and are called monatomic molecules

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18
Q

describe the melting and boiling point of a pure substance

A

they will be fixed temperatures (it will not melt and boil over a range)

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19
Q

describe the melting and boiling point of a mixture

A

mixtures usually melt or boil over a range of temperatures.

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20
Q

the narrower a range a substance melts and boils over…

A

the purer the subtance is

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21
Q

filtration

A

to separate an (undissolved) solid from a mixture of the solid and a liquid/solution

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22
Q

evaporation

A

to separate a dissolved solid from a solution, when the solid has similar solubilities in both cold and hot solvent

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23
Q

crystallisation

A

to separate a solute from a solution

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24
Q

simple distillation

A

to separate a liquid from a solution

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25
Q

fractional distillation

A

to separate two or more liquids that are miscible with one another (separate a mixture of liquids)

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26
Q

paper chromatograpy

A

to separate substances that have different solubilities in a given solvent.

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27
Q

Rf =

A

distance travelled by solute / distance travelled by solvent

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28
Q

what is thermal decomposition

A

when the elements in a compound that are chemically joined together are heated, and the compound decomposes into the elements.

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29
Q

where are the protons and neutrons in an atom

A

the nucleus

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30
Q

what is the relative charge of a neutron

A

0

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31
Q

what is the relative charge of a proton

A

+1

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32
Q

what is the realtive charge of a electron

A

-1

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33
Q

what is the relative mass of a proton

A

1

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34
Q

what is the relative mass of a neutron

A

1

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35
Q

what is the relative mass of an electron

A

virtually nothing 1/1836

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36
Q

what is the atomic number

A

number of protons in the nucleus of an atom of an element

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37
Q

what is the mass number

A

number of protons + number of neutrons in the nucleus of an atom of an element

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38
Q

what are isotopes

A

atoms (of the same element) which have the same atomic number but different mass numbers. they have the same number of protons but different numbers of neutrons

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39
Q

what is the relative atomic mass calculated from

A

from the masses and relative abundances of all the isotopes of a paticular element.

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40
Q

what is the symbol for relative atomic mass

A

Ar

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41
Q

where are electrons in an atom

A

around the nucleus in different energy levels called electron shells

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42
Q

what is electronic configuration

A

the way electrons are arranged

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43
Q

how many electrons can the first shell take

A

maximum of 2

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44
Q

how many electrons can the second shell take

A

maximum of 8

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45
Q

how many electrons can the third shell take

A

18

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46
Q

what are periods in the periodic table

A

the horizontal rows

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47
Q

what are groups in the periodic table

A

the vertical columns

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48
Q

what is a pattern within groups

A

elements with the same number of electrons in their outermost shell are in the same group

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49
Q

when do elements have similar chemical properties

A

when theyre in the same group

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50
Q

group 1 is called

A

the alkali metals because they all react with water to form alkaline solutions

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51
Q

group 7 is called

A

the halogens ‘salt - maker’ because they from salts when they react with metals.

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52
Q

group 8 is called

A

the noble gases because they are chemically unreactive as they have a full outer shell and so none gain or lose electrons easily

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53
Q

hydrogen’s ion

A

H+

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54
Q

lithiums ion

A

Li+

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55
Q

sodiums ion

A

Na+

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56
Q

potassiums ion

A

K+

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57
Q

rubidiums ion

A

Rb+

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58
Q

Caesiums ion

A

Cs+

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59
Q

beryilliums ion

A

Be2+

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60
Q

magnesiums ion

A

Mg2+

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61
Q

calciums ion

A

Ca2+

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62
Q

strontiums ion

A

Sr2+

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63
Q

bariums ion

A

Ba2+

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64
Q

borons ion

A

B3+

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65
Q

aluminiums ion

A

Al3+

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66
Q

galliums ion

A

Ga3+

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67
Q

silvers ion

A

Ag+

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68
Q

coppers ion

A

Cu2+

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69
Q

iron II ion

A

Fe(II)2+

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70
Q

iron III ion

A

Fe(III)3+

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71
Q

leads ion

A

Pb2+

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72
Q

zincs ion

A

Zn2+

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73
Q

ammoniums ion

A

NH4

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74
Q

nitrides ion

A

N3-

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75
Q

phosphides ion

A

P3-

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76
Q

asenides ion

A

As3-

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77
Q

oxides ion

A

O 2-

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78
Q

sulfides ion

A

S 2-

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79
Q

selenides ion

A

Se2-

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80
Q

tellurides ion

A

Te2-

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81
Q

fluroides ion

A

F-

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82
Q

chlorides ion

A

Cl-

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83
Q

bromides ion

A

Br-

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84
Q

iodides ion

A

I-

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85
Q

hydroxides ion

A

OH-

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86
Q

carbonates ion

A

CO3 2-

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87
Q

nitrates ion

A

NO3 -

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88
Q

sulfates ion

A

SO4 2-

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89
Q

what are the four different state symbols

A

s - solid
l - liquid
g - gas
aq - aqueous

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90
Q

what is the symbol for relative formula mass

A

Mr

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91
Q

how do you calculate Mr

A

add up the relative atomic masses of all the atoms present in the formula

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92
Q

what is a mole

A

a measure of the amount of substance. one mole is the amount of substance that contains 6.022 x 10 to the power of 23 particles.

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93
Q

what is the mass of one mole of atoms

A

the relative atomic mass expressed in grams

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94
Q

amount in moles =

A

mass of substance in grams / Mr

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95
Q

what is the empirical formula

A

the simplest whole number ratio of atoms of each element in the compound

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96
Q

what is the molecular formula

A

the exact numbers of atoms of each element present in the formula of the compound

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97
Q

what is the molar volume of a gas

A

one mole or any gas has a volume of 24dm cubed (24,000 cm cubed) at room temperature and pressure (r.t.p.)

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98
Q

how do you calculate volume of gas from amount of gas

A

volume of gas (in dm cubed) = amount x 24

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99
Q

1dm cubed =

A

1000 cm cubed

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100
Q

how do you calculate amount of gas from volume of gas

A

amount of gas (in moles) = volume of gas / 24

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101
Q

amount of dissolved substance =

A

(volume of solution x concentration of solution mol/dm )
____________________________
1000

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102
Q

what is an ion

A

an electrically charged atom or group of atoms formed by the loss or gain of electrons

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103
Q

when is an ionic lattice formed

A

when an ionic compound forms, the positively charged ions attract the negatively charged ions and arrange themselves in to a three - dimensional structure called an ionic lattice.

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104
Q

what is an ionic bond

A

the electrostatic force of attraction between the oppositely charged ions within an ionic lattice.

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105
Q

why do ionic compounds have high melting and boiling points

A

the electrostatic forces are strong and there are many of them to break apart, so it requires a large amount of energy to overcome the forces.

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106
Q

when a non - metal and a metal combine what do they form

A

an ionic bond

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107
Q

when a non - metal and a non - metal combine what do they form

A

a covalent bond

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108
Q

when a covalent bond is formed why is the new substance described as a simple molecular compound

A

because it consists of indiviual molecules

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109
Q

what does diatomic mean

A

the molecule contains two atoms

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110
Q

what is a displayed formula

A

use an unbroken line to represent a shared pair of electrons / single covalent bond instead of dots and crosses

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111
Q

do simple molecular substances have low or high melting and boiling points?

A

low because the forces of attraction between the molecules are typically weak compared to the eletrostatic forces of attraction between oppositely charged ions and very little energy is needed to overcome them.

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112
Q

what is a giant covalent structure

A

millions of atoms covalently bonded together like diamond, graphite and silicon dioxide

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113
Q

what are properties of diamond

A

very high melting point as many strong covalent bonds have to be broken, hard and abrasive and does not conduct electricity.

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114
Q

properties of graphite

A

very high melting point, soft and slippery and conducts electricty.

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115
Q

forces in diamond

A

strong covalent bonds

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116
Q

forces in graphite

A

strong covalent bonds and weak forces of attraction

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117
Q

how is diamond bonded

A

each carbon atom forms four single covalent bonds and a 3D structure is formed.

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118
Q

how is graphite bonded

A

each carbon atom forms three single bonds to other carbon atoms and a layered structure is formed.

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119
Q

uses for diamond

A

cutting tools

jewellery

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120
Q

uses for graphite

A

lubricant

electrodes for electrolysis

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121
Q

what is C60 fullerene

A

an allotrope of carbon

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122
Q

what is an allotrope

A

different forms of the same element

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123
Q

does C60 have low or high melting and boiling points

A

only the weaker intermolecular forces of attraction need to be broken so low.

124
Q

does C60 conduct electricity

A

no as each carbon atom only forms 3 bonds there are delocalised electrons in C60 but these electrons are only free to move within molecules and not between them

125
Q

how are metals arranged

A

in a giant, three - dimensional lattice structure in which postive ions are arranged in a regular pattern in a ‘sea of electrons’.

126
Q

what is the metallic bond in metals

A

the attraction between the delocalised electrons (detached from their atoms) and the positive ions.

127
Q

why do metals have high melting and boiling points

A

metallic bonds are strong and there are many of them in a giant structure, hence a lot of heat energy is required.

128
Q

why are metals good conductors of electricity

A

the delocalised electrons are free to move when voltage is applied across the metalk

129
Q

why are metals malleable and ductile

A

the layers of positive ions can easily slide over one another and take up different positions. the delocalised electrons move with them so the metallic bonds are not broken.

130
Q

do ionic compounds conduct electricity as a solid

A

no because the ions are not free to move.

131
Q

do ionic compounds conduct electricity when molten or when dissolved

A

yes because electrolysis takes place.

132
Q

what is electrolysis

A

the decomposition (chemical breakdown) of an ionic substance by passing an electric current through it.

133
Q

the substance being electrolysed is called the

A

electrolyte

134
Q

the electical connections between the electrolyte and the external electrical circuit are called

A

electrodes.

135
Q

the positive electrode is called an…

A

anode

136
Q

the negative electrode is called a…

A

cathode

137
Q

when electrolysing a molten binary compound, where is the metal formed?

A

at the negative electrode (cathode)

138
Q

when electrolysing a molten binary compound, where is the non-metal formed?

A

at the postive electrode (anode)

139
Q

explain the reaction at the cathode

A

positive metal atoms are attracted to the negative electrode. when they get to the electrode, they gain electrons and are reconverted back into their atoms.

140
Q

explain the reaction at the anode

A

negative non-metal ions are attracted to the positive electrode. when they get to the electrode, they lose electrons to form atoms. the atoms then then pair up to form molecules.

141
Q

in electrolysis of aquous solutions, the product at the negative electrode is either…

A

hydrogen or a metal

142
Q

in electrolysis of aqueous solutions, the product at the positive electode is either…

A

oxygen or another non-metal

143
Q

in electrolysis of aqueous solutions, what happens if the metal in the salt is above hydrogen in the reactivity series?

A

hydrogen is evolved at the cathode.

144
Q

in electrolysis of aqueous solutions, what happens if the metal in the salt is below hydrogen in the reactivity series

A

the metal is deposited on the cathode

145
Q

describe C60 fullerene’s structure

A

it is a molecular covalent structure with weak intermolecular forces between each sphere.

146
Q

what is an electrolyte

A

liquid or solution that undergoes electrolysis

147
Q

what substances are often used as electrodes

A

carbon (inert), platinum, and other metals

148
Q

give an example of a molten substance that can be used an electrolyte

A

lead bromide

149
Q

if something loses electron(s) then it has been…

A

oxidised

150
Q

if something gains electron(s) then it has been…

A

reduced

151
Q

how would you show diffusion

A

fill the lower gas jar with bromine gas, and the top one with air. remove the gas lids, and the brown colour of the bromine will diffuse upwards, whilst the air diffuses downwards until it is all a uniform brown .

152
Q

how would you show that particles of different gases travel at different speeds

A

soak a piece of cotton wool in ammonia, and another piece in hydrochloric acid. place these at either end of a long glass tube with rubber bungs to stop the poisonous gas from escaping. the particles will diffuse along the tube, forming a white ring considerably closer to the end containing hydrochloric acid. this is because ammonia particles are lighter and so move faster.

153
Q

how would you show diffusion through a liquid

A

fill a gas jar with water, then add a small jar of strongly coloured solution, such as potassium manganate. this will diffuse upwards and colour the whole solution purple.

154
Q

what is solubility measured in

A

g per 100g of water

155
Q

when is a compound formed

A

when two or more elements chemically combine.

156
Q

when is a mixture formed

A

when various substances are mixed together and no chemical reation occurs

157
Q

do properties of elements change in a mixture

A

no, the elements keep the same properties

158
Q

do properties of compounds change in a mixture

A

yes

159
Q

mass number is

A

protons + neutrons

160
Q

atomic number is

A

protons = electrons

161
Q

how do you work out number of neutrons from the periodic table

A

mass number - atomic number

162
Q

what is relative atomic mass

A

average mass of an atom, taking into account the amount of each isotope present in a naturally occuring sample of the element.

163
Q

as the shells of an electron get further away, and the distance increases, what happens to the energy

A

it increases

164
Q

elements in the same group contain

A

elements with similar properties.

165
Q

do metals or non-metals conduct electricity

A

metals

166
Q

what do metals generally form

A

basic oxides

167
Q

what is a basic oxide

A

one which reacts with acids to form salts

168
Q

what do non-metals generally form

A

acidic oxides

169
Q

what is an acidic oxide

A

acidic oxides react with bases/alkalis to form salts.

170
Q

properties of metals:

A 
high melting and boiling points
shiny
malleable
ductile
good conductors
form ionic compounds
form positive ions in their compounds (give away their electrons)
171
Q

properties of non-metals

A

tend to have low melting and boiling points
brittle when solid
not as shiny
not conductors (except carbon in the form of graphite for electricity, and diamond for heat)
form both ionic and covalent compounds
tend to form negative ions in ionic compounds

172
Q

what does the state symbol (s) mean

A

solid

173
Q

what does the state symbol (l) mean

A

liquid

174
Q

what does the state symbol (aq) mean

A

an aqueous solution

175
Q

what does the state symbol (g)

A

gas

176
Q

what is Ar

A

the atomic mass of an element

177
Q

what is the relative atomic mass of an element

A

the weighted average mass of the isotopes of an element. it is measured on a scale on which a carbon-12 atom has a mass of exactly 12.

178
Q

what is Mr

A

relative formula mass

179
Q

what is relative formula mass sometimes called

A

relative molecular mass

180
Q

how do you find Mr

A

add up all the Ar’s of the formula.

181
Q

how do you find Ar

A

it’s the mass number

182
Q

how do you find percentage by mass of a Ar of a compound

A

calculate the Ar’s, then divide the Ar you want to find the percentage mass of, by the total Mr of the compound. then multiply this by 100.

183
Q

how would you find the formula of magnesium oxide by combustion in a practical

A

weigh a crucible with a lid.
place a piece of magnesium ribbon about 10cm long in the crucible.
reweigh it and its contents.
set up the apparatus with the crucible above a bunsen burner on a tripod held in place by a pipeclay triangle.
heat strongly, lifting the lid every few seconds.
when the reaction is finished, allow everything to cool.
weigh everything again.

184
Q

why does the mass of magnesium increase when you heat it strongly

A

it combines with the oxygen in the air. the mass of magnesium oxide is greater than the mass of just magnesium.

185
Q

how would you find the formula of a metal oxide by reduction in a practical

A

weigh a ceramic dish.
put about 3g of copper oxide in the dish and reweigh.
place in a tube.
pass hydrogen gas over the copper oxide.
ignite the excess hydrogen, which comes out of the small hole in the boiling tube.
heat the copper oxide strongly until the reaction is finished. the copper will turn pink-brown.

186
Q

why does the mass of the copper oxide decrease when you heat it strongly

A

the oxygen leaves the copper and combines with the hydrogen to form water.

187
Q

how would you find the formula of water in a practical

A

use the practical to find the formula of metal oxide by combustion but put a U tube in beaker filled with ice and water connecting a pump and the release of hydrogen gas. this means the water vapour produced will condense.

188
Q

how do you calculate empirical formula

A

work out the number of moles in each element in the compound, then divide by the smallest result.

189
Q

how do you calculate percentage yield

A

actual yield
————————— x 100
theoretical yield

190
Q

what do you need to do when calculating the substance inexcess

A

use the molar ratio

191
Q

what is avogadros law

A

equal volumes of gases at the same temperature an pressure contain equal numbers of molecules

192
Q

what happens when an ionic compound is formed

A

electron(s) are transferreed from a metal atom to a non-metal atom to form positive and negative ions

193
Q

what is ionic bonding (def)

A

the strong electrostatic attraction between positive and negative ions

194
Q

when an atom loses an electron it becomes…

A

positively charged

195
Q

when an atom gains an electron it becomes..

A

positively charged

196
Q

what is a positive ion called

A

a cation

197
Q

what is a negative ion called

A

an anion

198
Q

what do elements in groups 1,2,6 and 7 always form

A

ions that are isoelectronic with the nearest noble gas atom

199
Q

how do you work out the charge on an ion

A

look at what group its in

200
Q

what do all metals form

A

positive ions

201
Q

what do names like lead(II) chloride mean

A

that it contains a Pb 2+ ion

202
Q

ion for zinc

A

Zn 2+

203
Q

ion for silver

A

Ag +

204
Q

ion for hydrogen

A

H +

205
Q

ion for ammonium

A

NH4 +

206
Q

ion for nitrate

A

NO 3-

207
Q

ion for hydroxide

A

OH -

208
Q

ion for carbonate

A

CO 3 2-

209
Q

what happens if you have an ‘ate’ ending not an ‘ide’ ending

A

it means the compound contains oxygen and possibly other things

210
Q

what is a lattice

A

a regular array of particles

211
Q

what do all ionic compounds form crystals that consist of

A

lattices of positive and negative ion spacked together in a regular way

212
Q

what is the lattice held together by

A

strong electrostatic attractions between the positively and negatively charged ions

213
Q

why do we call it a giant ionic latticw

A

to describe a structure where there are no indiviual molecules

214
Q

charactersititcs of ionic substances

A

they tend to be soluble in water

they tend to be insoluble in organic solvents

215
Q

why dont ionic compunds conduct electricity when theyre solid

A

the ions are fixed in posistion and are not free to move around.

216
Q

why do ionic compounds conduct electricity when theyre molten or dissolved in water

A

the ions become free to move aroumd.

217
Q

why do ionic compunds have high melting and boilingpoints

A

because of the strong electrostatic forces of attraction holding the lattice together. a lot of enegy has to be supplied to break the strong electrostatic forces of attraction between oppostielt charged ions in the giant lattice structure.

218
Q

what is a covalnet bond

A

a pair of electrons is shared between two atoms.

219
Q

what holds the atoms together in a covalent bond

A

the strong electrostatic attraction between the nuclei (positively charged) of the atoms that make up the bond and the shared pair of electrons (negatively charged)

220
Q

why are hydrogen molecules said to be diatomic

A

they contain two atoms

221
Q

what defines an element

A

how many protons it has

222
Q

the more bonds are formed..

A

the more energy is released and the more stable the system becomes.

223
Q

what is a double (covalent) bond

A

when two pairs of electrons are shared betweeen atoms.

224
Q

what is a triple (covalent) bond

A

when three pairs of electrons are shared between atoms

225
Q

what does intermolecular mean

A

between molecules

226
Q

describe the forces in watrer

A

strong covalent bonds between the H and O atoms,

intermolecular molecules, (between molecules) to keep it in liquid state

227
Q

when we boil water which forces are broken

A

the intermolecular ones, NOT the strong covalent bonds

228
Q

between what does ionic bonding ususally occur

A

a metal and a non metal

229
Q

between what does covalent bonding usuallly occur

A

a non metal and a non metal

230
Q

when do we say a substance has a simple molecular structure

A

when a substance consists of molecules with intermolecular forces of attraction between them

231
Q

why do substances with simple molecular structures tend to be gases or liquid with low melting and boiling points

A

not much energy is required to break the weak intemolecuakr bonds

232
Q

what do halogens all have

A

a simple molecular structure consisting of diatomic molecules with intermolecular forces between them.

233
Q

as relative molecular mass increases…

A

the intermolecular forces of attraction become stronger, so more energy must be put in to break the intermolecular forces.

234
Q

do covalent molecular compounds conduct electricity

A

no because they dont have nay overlal electrical charge

235
Q

are covalent molecular substances soluble

A

no they tend not to be in water, but often in organic solvents

236
Q

does diamond have high or low boiling points

A

very high

237
Q

why does diamond ahev very high melting and boiling points

A

because of the very strng carbon-carbon covalent bonds which extend throughout the entire crystal in three dimensions. a lot of enrgy has to be supplied to break these.

238
Q

does diamond haev intermolecular forces

A

no, it has a giant structure, there are no molecules.

239
Q

what is diamond a form of

A

pure carbon

240
Q

other characteristics of diamond

A 
very hard (los of energy to break the covalent bonds)
doesnt conduct electricity (no electrons can move around)
241
Q

difference between graphite and diamond

A

in graphite, it has a layer structure, each layer is strong, but they are easily separated from another layer.

242
Q

is graphite hard or soft

A

soft, the forces holdinga toms together in each layer are strong,but he attactions between layers are much weaker and not much energy is needed to overcome them. layers slide over eachother and can easily be flaked off.

243
Q

other characteristiics of graphite

A

high melting and boiling points because you have to break up the whole structure.
it conducts electricity because each carbon atom is joined to only three others, meaning one is free to mvo around throughout the whole of the layer. this is called a delocalised electron

244
Q

what are diamon and carbon

A

allotropes of carbon

245
Q

what strucutes do diamond and carbon have

A

giant

246
Q

what structure doe C60 have

A

simple molecular

247
Q

in solid or liquid C60, there are…

A

C60 molecules with weak intermoleular forces between them. (60 carbon atoms joined by covalent bonds)

248
Q

charicterstics of C60 or fullerene

A

lower melting and boiling points, when it’s melted, only the relatively weak intermolecular forces of attraction must be broken. this does not require as much energy as breaking all the strong covalent bond when diamond and graphite are melted
not as hard as diamond (doesnt take as much energy to break the intermolecular forces of attraction)
does not conduct electricity because the fouth electron on each carbon atom cannot jump from molecule to molecule

249
Q

describe the bonding in a giant ionic lattice structure

A

positive and negative ions in a regular arrangement. the oppositely charged ions will be attracted to eachother by electrostatic forces

250
Q

where would non-metal oxides be on the pH scael

A

4 because theyre (usually) acidic

251
Q

group of noble gases

A

0

252
Q

C60 is

A

a simple molecular substance that contains delocalised electrons

253
Q

explain how the pattern of spots produced in a paper chromatography experiment can be used to distinguish a pure substance from an impure substance

A

a pure substanace leaves a single spot, and impure substance leaves multiple spots

254
Q

why are the noble gases not very reactive

A

they don’t easily lose or gain electrons

255
Q

describe the bonding in a giant ionic lattice structure like sodium chloride

A

oppositely charged ions are attracted to eachother by electrostatic forces

256
Q

solubility def

A

maximum mass of solute that dissolves in 100g of solvent at a particular temperature.

257
Q

saturated solution def

A

a solution which contains as much dissolved solid as possible at a particular temperature. there must be some undissolved solute present.

258
Q

what can you use solubility curves for

A

to work out what mass of crystals you would get if you cooled a saturataed solution.

259
Q

what is avogadros law

A

equal volumes of gases at the same temperature and pressure contain equal numbers of molecules

260
Q

what are volumes of gases or liquids are measured in

A

cubic centimetres
cubic decimetres
litres

261
Q

link between litres, cubic decimetres and cubic centimetres

A

1 litre = 1dmcubed = 1000cmcubed

262
Q

convert 1dmcubed to 1000cmcubed

A

multiply by 1000

263
Q

convert 1000cm cubed to 1dmcubed

A

divide by 1000

264
Q

1 mole of any gas contains the

A

same number of molecules and so occupies the same volume as 1 mole of any other gas at the same temperature and pressure

265
Q

at room temp and pressure, what is the volume occupied by 1 mole of any gas?

A

24dmcubed or 24,000cmcubed

266
Q

volume of a gas =

A

number of moles x molar volume (24dmcubed)

267
Q

what are concentrations measured in

A

g/dmcubed

mol/dmcubed

268
Q

number of moles =

A

concentration (mol/dmcubed) x volume of solution (dmcubed)

269
Q

what is a titration

A

the technique to find out how uch of one solution reacts with a certain volume of another solution of known concentration.

270
Q

wahat is measured into a conical flask in a titration using what

A

a solution of an alkali using a pippette.

271
Q

where is the acid run from in a titration

A

a burette.

272
Q

as the acid in a titration is run into the conical flask of an alkali, what must you do

A

swirl it constantly.

273
Q

what happens near the end of a titration

A

the acid is run in a drop at a time until the indicaotr just changes colour.

274
Q

if you know the concentration of the acid or alkali in a titration what can you do

A

use the results of the concentration to calculate the concentration of the other solution you reacted it with.

275
Q

what is a metallic structure

A

a lattice of positive ions in a sea of delocalised electrons

276
Q

what happens when metal atoms bond together

A

they form the solid metal, meaning the outer electron on each sodium atom becomes free to move throughout the whole structure. these electrons are said to be delocalised.

277
Q

what are delocalised electrons

A

electrons that are no longer attatched to particular atoms or pairs of atoms, instead they ‘flow through the whole metal’.

278
Q

what is metallic bonding

A

the electrostatic forces of attraction between each positive ion and the delocalised electrons. this holds the structure together.

279
Q

what type of structure do metals have

A

giant structures.

280
Q

are there any indiviual molecules in metal giant structures

A

no all the positive ions in the lattice attract all the delocalised electrons

281
Q

what does the ion formed by the metal depend on (in metallic bonding)

A

then number of electrons the original atoms has in its outer shell.

282
Q

describe the melting points of metals

A

high due to the strong electrostativ forces of attraction betwen the positive ions and the delocalised electrons in a giant metallic strucutre

283
Q

describe the electrostatic forces of attraction between the positive ions and the delocalised electrons in a giant metallic structure

A

strong (leading to the metal’s high melting point)

284
Q

why do metals conduct electricity

A

the delocalised electrons are free to move throughout the structure.

285
Q

what happens when force is applied to a piece of metal

A

the layers of positive ions slide over eachother. this does not affect bonding, the positive ions are still attracted to the delocalised electrons. this means metals are malleable.

286
Q

why dont ionic compounds conduct electricity when they are solid

A

the ions are held tightly in position in the lattice and they are not free to move around.

287
Q

why do ionic compounds conduct electricity when molton or dissolved in water

A

the ions are now free to move around

288
Q

do covalent molecular compounds conduct electricity

A

no never, they consist of indiviual molecules without any overall electrical charge, so there are no charged particles to move around. the electrons are also all held tightly in the atoms or in covalent bonds and so they are not able to move from molecule to molecule.

289
Q

what is electrolysiss

A

a chemical change caused by passing an electric current through a compound which is either molten or in solution.

290
Q

what is an electrolyte

A

a liquid or solution that undergoes electrolysis. they all contain ions. the movement of the ions is responsible for both the conduction of electricity and the chemical changes that take place.

291
Q

what are electrodes

A

the way electricity is passed into and out of the electrolyte

292
Q

what material is commonly used for electrodes

A

carboin because it conducts electricity and is chemically fairly inert, so it doesnt react with things. platinum can be usedinstead.

293
Q

when you connect a power source in electrolysis, what happens

A

it pumps mobile electrons away from one electrode to the next one. as there are more electrons there, it has a negative charge (the cathode). the other electrode has had electrons removed from it so is positively charged. (the anode). then the cations are attracted to the cathode (and gain electrons to form neutral charges) and the negative ions (anions) are attracted to the anode (and lose electrons to form neutral charges)

294
Q

what does discharging an ion mean

A

that it loses its charge.

295
Q

how does discharging an ion happen

A

by giving up eletrons to the electrode or receiving electrons from it

296
Q

what is oxidation

A

when something loses electrons

297
Q

what is reduction

A

when something gains electrons

298
Q

what happens if you electrolyse a molten ionic compound only containing two elements,

A

you will get the metal at the cathode (because metals form positive ions) and the non-metal at the anode (because non-metals form negative ions

299
Q

where does reduction always occur at in electrolysis of molten substances

A

reduction always occurs at the cathode and oxidation always occurs at the anode.

300
Q

cations are attraced to

A

the cathode

301
Q

anions are attracted to

A

the anode

302
Q

why would it be easier to add an ion to a less reactive metal than a reactive on

A

the reactive one will just lose it again, so it would be better to add it to the unreactive one

303
Q

what is water called

A

a weak electrolyte.

304
Q

what does water ionise to give

A

hydrogen and hydroxide ions.

305
Q

why do ions have to be present for electrolysis to work

A

the current in the external circuit can only flow if there are ions which can move and be discharged. if you tried to electrolyse a covalent compound (either molten or in solution (there wouldn’t be a current flow because there aren’t any ions)

edexcel igcse chemistry (4 decks)

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