Chemistry PPE revision Flashcards
1
Q
what is an atom?
A
smallest part of an element that can exist
2
Q
What is the radius of an atom?
A
1x10 to the power of -10 m
3
Q
What is the radius of the nucleus of an atom?
A
1x10 to the power of -14 m
4
Q
What is an element?
A
Substances made up of only one type of atom
5
Q
what is a compound?
A
.A substance containing two or more different elements, chemically combined
6
Q
What is the only way compounds can be separated into elements?
A
By chemical reactions
7
Q
What is a chemical reaction?
A
Always involves the formation of one or more new substances and often involve an energy change
8
Q
What is the charge of a proton and where are they found?
A
Positively charged and found in the nucleus
9
Q
What is the charge of a neutron and where are they found?
A
No charge (neutral) and found in the nucleus
10
Q
What is the charge of an electron and where are they found?
A
Negatively charged and found in shells around the nucleus
11
Q
What is the relative charge and relative mass of a proton?
A
Relative charge: +1
Relative mass: 1
12
Q
What is the relative charge and relative mass of a neutron?
A
Relative charge: 0
Relative mass: 1
13
Q
What is the relative charge and relative mass of an electron?
A
Relative charge: -1
Relative mass: 1/2000 (very small)
14
Q
Where is almost all of the mass of an atom found?
A
In the nucleus
15
Q
What is an isotope?
A
Atoms of the same element that have the same number of protons but a different number of neutrons
16
Q
What is an ion?
A
A charged particle that forms when an atom or molecule gains or loses electrons
17
Q
Where are electrons found?
A
In shells (sometimes referred to as energy levels)
18
Q
How many electrons can fit in the first shell of an electron?
A
Up to 2
19
Q
How many electrons can fit in the second shell of an electron?
A
Up to 8
20
Q
How many electrons can fit in the third shell of an electron?
A
Up to 8
21
Q
What is the mass number?
A
The number of protons + neutrons
22
Q
What is the atomic number?
A
The number of protons
23
Q
Why do atoms have no overall charge?
A
There is the same number of positive protons and negative electrons that cancel each other out
24
Q
What must negatively charged ions have?
A
One more electron than proton
25
What is relative atomic mass?
The average mass of all the atoms of an element
26
What is the equation to calculate relative atomic mass?
Relative atomic mass = (mass of isotope 1 x percent abundance of isotope 1) + (mass number of isotope 2 x percent abundance of isotope 2) / 100
27
What is a mixture?
A mixture consists of two or more elements or compounds not chemically combined
28
What are the different ways mixtures can be separated?
.filtration
.crystallisation
.simple distillation
.fractional distillation
.chromatography
29
What is filtration used for?
To separate mixtures of insoluble solids (eg sand) and liquids (eg water)
30
what happens during filtration?
.pour a mixture of insoluble solid and liquid through some filter paper
.the insoluble solid will then stay in the filter paper because its particles are to large to pass through
.and the liquid passes through the filter paper and will gather in the flask
31
When is simple distillation used?
To separate a solvent from a solution when we want to keep the liquid
Eg. producing water from salt solution
32
What happens during simple distillation?
.the solution is heated using a Bunsen burner
.the liquid part evaporates and becomes a vapour, rising up
.the vapour passes through the condenser where it is cooled
.when the vapour is cools it will condense back down to a liquid
.this then separates the liquid from the dissolved solid
33
When is fractional distillation used?
To separate two or more liquids with different boiling points
34
What happens during fractional distillation?
.The mixture is heated to the temperature of the liquid with the lowest boiling point
.the liquid with the lowest boiling point will evaporate first
.it will pass up through the fractionating column and through condenser where it cool and condenses
.when all of this substance has evaporated and condensed we have the two liquids
35
When is crystallised used?
to separate a dissolved solid from a solution
36
What happens during crystallisation?
.gently heat the mixture in a evaporating basin
.some of the solvent (eg water) will evaporate making the solution more concentrated
.remove from heat when crystals begin to form
.leave to cool and filter to remove excess liquid
.leave the crystal to dry
37
When is chromatography used?
To separate mixtures of coloured compounds
38
What happens during chromatography?
.A spot of the mixture is placed on a pencil line near the bottom of a piece of chromatography paper
.paper is placed vertically upright in a solvent (eg water)
.the solvent is soaked up by the paper, carrying the different components with it
.different components move at different rates. This separates them
.if we had a mixture, we would see the spot move up the chromatography paper, and separate and give us two different spots or more
39
Why is pencil used in chromatography?
It is insoluble in water so it doesn’t move
40
What was Daltons model of the atom like?
.an atom is a solid sphere that cannot be created, destroyed or divided into smaller parts
.different types of spheres make up different elements
.the sphere does not contain protons, neutrons or electrons
41
Who made the plum pudding model?
J.J Thomson
42
Who made the plum pudding model?
J.J Thomson
43
What did J.J Thomson discover about the atom?
.The atom is not a solid sphere
.A cloud of positive charge with negative electrons embedded within it
44
Who made the nuclear model?
Rutherford
45
What is rutherfords alpha scattering experiment?
.He fired alpha particles at a thin sheet of gold foil
.If the plum pudding model was true, the alpha particles would bounce back
.however, most passed straight through
.some were deflected and very few bounced straight back
46
What were the results of the alpha scattering experiment?
.The mass of an atom is concentrated in a central nucleus
.the nucleus had to be positively charged to repel the positive alpha particles
.most of the atom was empty space as most passed straight through
47
Who made the electron shell model?
Bohr
48
Who made the electron shell model?
Bohr
49
What did Bohr discover about atoms?
.electrons orbit the nucleus at specific distances in shells/energy levels
50
Who discovered the neutron?
James Chadwick carried out experiments that provided evidence to show the existence of neutrons in the nucleus
51
Why is it called the periodic table?
Similar properties occur at regular intervals
52
What are the columns called on the periodic table?
Groups
53
What are the rows called on the periodic table?
Periods
54
What are groups within the periodic table?
Elements with similar properties are arranged in columns known as as groups
55
What do elements in the same group have?
The same number of electrons in their outer shell
56
What does the group number tell us about an element?
How many electrons are in the outer shell of
57
What do elements in the same period have?
The same number of electron shells
58
How did scientists arrange elements before the discovery of protons, neutrons and electrons? And what was the fault of this?
.In order of atomic weight
.some elements were placed into incorrect groups as their chemical properties were ignored
59
Why did Mendeleev leave gaps in his periodic table?
To leave room for undiscovered elements
60
What are elements that react to form positive ions?
Metals
61
What are elements that react to form negative ions?
Non-metals
62
Where are metals found on the periodic table?
To the left hand side of the periodic table
63
Where are non metals found on the periodic table?
To the right hand side of the periodic table
64
What are the properties of group 0 elements?
.full outer shell of electrons
.unreactive
.do not form molecules. They exist as Ne, He, etc
65
Why are group 0 elements unreactive?
Because they have a full outer shell of electrons
66
How does the boiling point of the group 0 elements change down the group?
The boiling point increases
67
What are the properties of group 1 elements?
.1 electron in their outer shell
.react with oxygen, chlorine and water
68
What are the properties of group 1 elements?
.1 electron in their outer shell
.react with oxygen, chlorine and water
69
How does the reactivity of the group 1 elements change down the group? And why does this happen?
.Reactivity increases
.the atoms increase in size
.there are more shells, so the outer shell is further away from the nucleus
.the electrostatic attraction between the nucleus and the electron is weaker
.so it is easier to lose the one outer electron
70
What is the equation for reactions with water in group 1?
Metal + water -> metal hydroxide + hydrogen
71
why do group 1 elements get given the name “alkali metals”?
When they react with water, they form an alkali
72
What is given off during reactions with water?
Heat
73
What is observed when alkali metals react with water?
.fizzing due to the formation of hydrogen gas
.the solid metal disappears because the metal gets used up
74
What is the equation for reactions with oxygen in group 1?
Metal + oxygen -> metal oxide
75
What is the equation for reactions with chlorine in group 1?
Metal + chlorine -> metal chloride
76
What are the properties of group 7 elements?
.have 7 electrons in their outer shell
.they are non metals
.consists of pairs of atoms
77
How does the reactivity of group 7 elements change down the group?
Reactivity decreases
78
Why does the reactivity of the group 7 elements decrease down the group?
.the atoms increase in size
.more shells so the outer shell is further away from the nucleus
.the electrostatic attraction between the nucleus and the outer shell is weaker
.its harder to gain an electron to fill the outer shell
79
Why does the melting and boiling point of the group 7 elements increase down the group?
.the molecules increase ib size
.the intermolecular forces become stronger
.more energy required to overcome the forces of attraction
80
What is the state of fluorine, chlorine, bromine and iodine at room temperature?
Fluorine- Gas
Chlorine- Gas
Bromine- Liquid
Iodine- Solid
81
How does the relative molecular mass change down group 7 elements?
Increases down the group
82
What is the appearance of group 7 elements at room temperature?
Fluorine- yellow
Chlorine- yellow-green
Bromine-red-brown
Iodine- grey
83
What is the colour in solution of group 7 elements?
Chlorine- pale green
Bromine- orange
Iodine- dark brown
84
What happens with group 7 reactions with metals?
They react with metals to produce salts
85
What happens with group 7 reactions with non metals?
When they react with hydrogen they form hydrogen halides
86
What is a displacement reaction?
When more reactive elements can take the place of less reactive elements in a compound
87
What happens when we react potassium chloride with bromine or iodine?
No reaction
88
What happens when we react potassium bromide with chlorine or iodine?
Chlorine- displaces bromine ions, orange colour observed
Iodine- no reaction
89
What happens when we react potassium iodide with chlorine and bromine?
Chlorine- chlorine displaces iodide ions, brown colour observed
Bromine- bromine displaces iodide ions, brown colour observed
90
what is melting?
going form a solid to a liquid
91
What is boiling?
going from a liquid to a gas
92
what is condensing?
Going from a gas to a liquid
93
What is freezing?
Going from a liquid to a solid
94
What is ionic bonding? And what does it occur between?
.the strong electrostatic attraction between oppositely charged ions
.metals and non metals
95
What happens during ionic bonding?
When a metal reacts with a non metal atom electrons from the outer shell of the metal atom are transferred. Metal atoms lose electrons and become positively charged ions, also known as cations
Non metals gain electrons and become negatively charged ions, also known as anions
after reacting both the metal and non metal ions have a full outer shell
96
What is an ionic compound?
.a giant lattice structure of ions held together by strong electrostatic forces of attraction between oppositely charged ions
97
What is an empirical formula?
The simplest whole number ratio of atoms or ions in a structure
98
What are advantages and disadvantages of a dot and cross diagram for ionic compounds?
Advantages:
Shows the transfer of electrons
Disadvantages:
.Doesn’t show hot the ions are arranged in 3D space
.doesn’t show relative sizes of the ions
99
What are advantages and disadvantages of the 3D ball and stick diagram for ionic compounds?
Advantages:
.shows the arrangement of ions in 3D space
Disadvantages:
.uses sticks for bonds which is misleading because the forces of attraction between ions act in all directions
.shows lots of free space between ions which isn’t actually there
100
What are advantages and disadvantages of a 2D diagram for ionic compounds?
Advantages:
.shows the arrangement of ions in one layer
Disadvantages:
.doesnt show the different layers of ions
.doesnt show the 3D arrangement in space
101
What are advantages and disadvantages of a 3D diagram for ionic compounds?
Advantages:
.shows the 3D arrangement in space
Disadvantages:
.not to scale
.gives no information about the forces of attraction between ions
102
What are the properties of ionic compounds
.high melting points
.high boiling points
.conducts electricity when melted or dissolved in water
.do not conduct electricity when in the solid state
103
Why do ionic compounds have high melting or boiling points?
.strong electrostatic attractions between oppositely charged ions
.large amounts of energy needed to overcome the forces of attraction
104
why do ionic compounds conduct electricity when melted or dissolved in water?
The ions are free to move and the charge can flow freely
105
What is a covalent bond?
A bond formed when electrons are shared between non metal atoms
106
What are substances with giant covalent structures?
Solids with very high melting points
107
What are examples of giant covalent structures?
.diamond- one of the hardest substances
.graphite- conducts electricity
.silicon dioxide- naturally found in sand- high melting and boiling point
108
Why do giant covalent structures have high melting points?
Because the many strong covalent bonds between atoms must be broken, this requires a lot of energy
109
Why do most giant covalent structures not conduct electricity?
Because they have no delocalised electrons or ions, they are free to move to carry charge.
110
What happens when boiling or melting substances made up of small molecules?
The weak intermolecular forces between molecules are overcome and this doesn’t require a lot of energy
111
What do bigger molecules have?
Stronger intermolecular forces, so they have higher melting and boiling points
112
Why do small molecules not conduct electricity?
They have no charge
113
What are polymers?
Very large molecules made up of many repeating units joined by covalent bonds
114
What are polymer chains held together by?
Intermolecular forces
115
Why are intermolecular forces between polymers really strong? And what does this mean?
.Because the polymer is such a long molecule
.this means polymers have higher melting points compared to smaller molecules and are solid at room temperature
116
What are polymers used for?
To make plastic
117
What are some advantages and disadvantages of using a dot and cross diagram for covalent compounds?
Advantages:
.show the transfer of electrons
.shows which atom the bonding electrons come from
Disadvantages:
.doesn’t show how the atoms are arranged in 3D space
.doesn’t show relative sizes of the atoms
118
What are some advantages and disadvantages of using a 3D ball and stick diagram for covalent compounds?
Advantages:
.shows the arrangement of atoms in 3D space
.shows shape of the molecule
Disadvantages:
.used sticks for bonds and doesn’t show that the bonds are forces
.atoms placed far apart from each other but in reality gaps are much smaller
119
What are some advantages and disadvantages of using a 2D diagram for covalent compounds?
Advantages:
.shows what atoms are in a molecule and how they are connected
Disadvantages:
.doesn’t show the relative size of the atoms and bonds
.doesnt show the 3D arrangement in space
120
What are some advantages and disadvantages of using a 3D diagram for covalent compounds?
Advantages:
.shows the 3D arrangement in space
Disadvantages:
.not scale
.gives no information about the forces of attraction between atoms
121
Describe the structure and bonding in diamond?
.giant covalent structure
.every carbon atom forms 4 strong covalent bonds with other carbon atoms
122
Why is diamond so hard?
.giant covalent structure
.every carbon atom forms 4 string covalent bonds with other carbon atoms so it requires a lot of energy to break
123
Why does diamond not conduct electricity?
.Every carbon atom forms 4 strong covalent bonds with other carbon atoms
.so there are no delocalised electrons or ions free to move
124
Describe the bonding and structure in graphite
.made of only carbon atoms
.forms hexagonal rings arranged in layers
.each carbon atom forms strong covalent bonds with 3 other atoms , this leaves carbon with one spare electron, this is delocalised and free to move through the layers
125
What are group 1 elements know as?
Alkali metals
126
What are group 2 elements known as?
Alkali Earth metals
127
What are group 7 elements know as?
The halogens
128
What are group 0 elements know as?
Noble gasses
129
What does graphite conduct electricity?
Each carbon carbon atom has one spare electron which is delocalised and free to move around and carry electrical charge through the layers
130
Why is graphite slippery?
The layers have weak intermolecular forces between them so it doesn’t require much energy to overcome
131
What is graphene?
A single layer of graphite
132
Graphene has strong covalent bonds between carbon atoms, what does this mean?
.it is very strong
.has high melting and boiling points
This is because it will take a lot of energy to break the strong covalent bonds
133
How many carbon atoms is graphene bonded to?
3
134
Is graphene a conductor of electricity?
Yes
135
What are fullerenes?
Molecules of carbon atoms with hollow shapes
136
How can fullerenes be arranged?
As a tube or as a ball
137
What is a property of a nano tube?
A high tensile strength so are difficult to break
138
What is a property of a nano tube?
A high tensile strength so are difficult to break
139
What are nanotubes useful for?
Nanotechnology, electronics and materials
140
What is a nanotube?
Cylindrical fullerenes with very high length to diameter ratios
141
What is a buckmister fullerene?
A molecule made up of 60 carbon atoms covalently bonded into a spherical shape
142
What are properties of buckmister fullerenes?
There are weak intermolecular forces between the molecules- this means buckmister fullerene has a low melting point and is slippery
143
What are buckmister fullerenes used for?
As a lubricant and for drug delivery
144
Why do metals have high melting and boiling points?
Because metals have giant structures of atoms with strong metallic bonding which means it requires a lot of energy to overcome to strong bonds
145
What are some properties, advantages and disadvantages of pure metals
.atoms are arranged in layers
.these layers can slide over each other which means that they can be bent and shaped
.pure metals can be to soft
146
How are alloys made and why are they better than pure metals
.If we mix pure metals with other elements we can make an alloy
.atoms of different elements are different sizes.The distorts the layers
.the layers can’t slide over each other as easily- more force is required
.this makes alloys harder and stronger than pure metals
147
What are properties of metals?
.made up of giant structures of atoms arranged in a regular pattern
.the electrons in the outer shell of the metal atoms are delocalised, forming metal ions
.these delocalised electrons are free to move through the layers of metal ions
148
Why can metals conduct electricity?
The delocalised electrons are free to move between the layers
149
Why are metals good conductors of thermal energy?
The delocalised electrons transfer energy
150
What causes metallic bonding?
The sharing of delocalised electrons
151
What is the law of conservation of mass?
No atoms are lost or made during a chemical reaction. The mass of the products equals the mass of the reactants
152
What happens to mass in an in closed system?
Mass will be observed to be conserved
153
What happens to mass in a non-enclosed system?
Gasses can enter and leave the system, this will make it look like the mass has changed when it hasn’t
154
What is relative formula mass?
The sum of the relative atomic masses of the atoms in the numbers shown in its formula
155
What is the equation to calculate percentage by mass?
Total relative atomic mass of atoms of the element/relative formula mass of compound x100
156
How can we calculate uncertainty?
.using the range of a set of repeated experiments
.looking at the resolution of the measuring instrument
157
How do we calculate uncertainty?
.work out the range of the results
.the uncertainty is half of the range
158
What is resolution?
The smallest division in apparatus
