Chemistry - EOY Flashcards
(100 cards)
1
Q
What is an atom?
A
The smallest part of an element that can exist
2
Q
What is an element?
A
A substance made up of only one type of atom
3
Q
Name the three subatomic particles
A
Protons, neutrons and electrons
4
Q
State the relative masses and charges of the subatomic particles
A
Mass: Proton: 1 Neutrons: 1 Electrons: negligible
Charge: Proton: +1 Neutrons: 0 Electrons: -1
5
Q
What is the plum pudding model?
A
A ball of positive charge with negative electrons studded into it
6
Q
What did the gold foil experiment (alpha particle scattering) prove?
A
That atoms have dense nuclei with a positive charge
7
Q
What did Chadwick discover?
A
The neutron
8
Q
What did Bohr’s experiment show?
A
That electrons are in specific shells
9
Q
What is the atomic number of an atom?
A
The number of protons in an atom
10
Q
What is the mass number of an atom?
A
The number of protons + the number of neutrons
11
Q
In the electron shell model, how are the subatomic particles arranged in an atom?
A
Protons and neutrons in the nucleus, electrons orbiting in shells
12
Q
Why is the number of electrons in atom equal to the number of protons?
A
As their charges cancel out
13
Q
How many electrons can go in the first shell?
A
2
14
Q
How many electrons can go in the second and third shells?
A
8
15
Q
What are the groups in the periodic table?
A
The columns numbered (1, 2, 3, 4, 5, 6, 7, 0)
16
Q
What can the group tell you about the electrons in an atom?
A
How many electrons are in the outer shell. E.g. carbon is in group 4 so has 4 electrons in the outer shell
17
Q
What are periods in the periodic table?
A
then rows
18
Q
What can the period tell you about the electron in an atom?
A
How many shells an atom has. E.g. Carbon is in the second period so has two shells
19
Q
Why do atoms have no overall charge?
A
The number of protons and neutrons are equal
20
Q
What are isotopes?
A
Atoms of the same element with a different number of neutrons
21
Q
What is abundance
A
The % of atoms in a sample with a particular mass
22
Q
What is the relative atomic mass of an element?
A
An average value for the mass that takes account of the abundance of the isotopes of the element
23
Q
What is relative formula mass?
A
The sum of the relative masses of each atom in a compound
24
Q
What symbol do we use for relative formula mass?
A
Mr
25
In the modern periodic table, how are the atoms rearranged?
By their atomic number and in groups according to their chemical properties
26
Why did Mendeleev leave gaps in his periodic table?
For elements that had not been discovered yet?
27
Why do elements in the same group have similar properties?
Because they have the same number of electrons in their outer shell
28
Before the discovery of protons, neutrons and electrons, how did scientists organise the elements?
By atomic weight
29
Which discovery meant that their organising elements by atomic weight was not always correct?
isotopes
30
Where are the metals on the periodic table found?
To the left and bottom of the periodic table
31
What name is given to elements in group 0?
Noble gases
32
Why are the group 0 elements so unreactive?
They have full outer shells so do not need to lose or gain electrons
33
How does the boiling points of group 0 change down the group?
Increases down the group
34
Explain why the group 1 elements are called alkali metals
They are metals that form alkalis when react with water
35
What are the products of the alkali metals in a reaction with: oxygen, water, halogens?
Oxygen: Metal oxide
Water: Metal hydroxide + hydrogen
Halogen: Metal halide
36
Explain why group 1 metals get more reactive down the group
More electrons, more shielding, weaker electrostatic from the nucleus to the outer shell, easier to lose an electron
37
What name is given to elements in group 7?
Halogens
38
How does the boiling point of group 7 elements change down the group?
Increases down the group
39
Explain why the group 7 elements get less reactive down the group
More electrons, more shielding, weaker electrostatic attraction from the nucleus to the outer shell, harder to gain ain electron
40
What is a displacement reaction?
Where a more reactive element displaces a less reactive one from a compound
41
Where are the transition metals found in the periodic table?
In the middle
42
Compare the melting point, density, strength, hardness and reactivity of transition metals with group 1 metals
Higher for all but reactivity
43
What is distinctive about the ions formed by transition metals?
Can form ions with different charges (e.g. Fe2+ and Fe3+)
44
What is distinctive about the compounds formed from transition metals?
They are coloured
45
What can transition metals be used for?
Catalysts
46
What happens to the electrons in an ionic bond?
They are transferred from the metal to the non-metal
47
If an atom has gained electrons, what charge will it have as an ion?
Negative
48
If an atom has lost electrons, what charge will it have as an ion?
Positive
49
What type of elements will form ionic bonds?
Metal + non-metal
50
What is the charge on elements in group one and in group two?
Group 1: 1+
Group 2: 2+
51
What is the charge on elements in group six and in group seven?
Group 6: 2-
Group 7: 1-
52
Describe the structure and bonding in an ionic compound
Giant ionic lattice held together by strong electrostatic force of attraction between positive and negative ions
53
State the melting point and boiling point of ionic compounds
High
54
Explain the melting and boiling point of ionic compounds
High due to strong electrostatic forces of attraction which require lots of energy to break
55
Explain why ionic compounds do not conduct electricity when solid
The ions are not free to move and carry a charge
56
Explain why ionic compounds conduct electricity when molten or in solution
The ions are free to move and carry a charge
57
What happens to the electrons in a covalent bond?
They are shared
58
What type of elements will form covalent bonds?
Non-metals
59
Explain why most covalent substances do not conduct electricity
There are no free electrons or ions that are free to move or carry a charfe
60
Describe the structure of small molecules
Strong covalent bonds between atoms, weak intermolecular forces holding the molecules together
61
Explain why the small molecules have low melting points
It is a simple molecular substance with weak intermolecular forces which are easy to break
62
Why do larger molecules have higher melting points than smaller ones?
Intermolecular force strengths with increased molecular size
63
What are the four state symbols and what do they stand for?
(s) - solid
(l) - liquid
(g) - gas
(aq) - aqueous
64
What is a mixture?
Something that contains several different substances not chemically bonded together
65
What is a compound?
A substance made up of two or more different types of atoms chemically bonded together
66
In everyday language what is a "pure" substance?
A substance that has had nothing added to it and is in its "natural" state
67
In chemistry what is a "pure" substance?
A substance made of a single element or compound
68
How can pure substances be distinguished from impure ones?
By their melting/boiling points
69
What are the melting and boiling points of pure substances?
One very specific temperature
70
What are the melting and boiling points of impure substances?
They change state at a range of temperatures
71
What is a formulation?
A mixture made to a specific recipe and designed for a specific purpose
72
Give examples of formulations
Paint, Detergents, Medicines, Cosmetics
73
What type of mixture can be separated by filtration?
A liquid and an insoluble solid
74
What is crystallisation / evaporation?
A process to separate a soluble solid from a solvent. The solution is heated to evaporate some of the solvent. It is the left to cool and form crystals
75
What is distillation?
A process that separates a liquid from a solution ( or mixture of liquids) by evaporating and then condensing the liquid
76
What is fractional distillation?
A process that separates a mixture of liquids that have similar boiling points
77
What is chromatography?
A process to separate the constituents of a mixture
78
How can chromatography show the difference between pure and impure substances?
Pure ones will not seperate into a number of spots
79
In chromatography, why must the substances be placed on a pencil line?
Pencil will not dissolve in the solvent (it is insoluble)
80
In chromatography why must the solvent height be lower than the pencil line?
So that the substances do not dissolve into the solvent of the paper
81
What is the conservation of mass?
That atoms cannot be created or destroyed
82
When a metal forms a metal oxide, why does the mass increase?
Because oxygen atoms from the air have been added
83
When an acid reacts with a metal, why does the mass decrease?
Because a gas is produced and escapes
84
What is the formula for a mean rate of reaction in terms or reactants?
Quantity of reactant used / Time taken
85
What is the formula for a mean rate of reaction in terms of product?
Quantity of product formed / Time taken
86
How can you measure the quantity of a reactant or product?
In grams or in cm3
87
What are the two possible units for a rate of reaction?
g/s or cm3 / s (where s is seconds)
88
What is "collision theory"?
The theory that chemical reactions only occur when particles collide with sufficient energy
89
What five factors can affect the rate of reaction?
Temperature, surface area or a solid, concentration of reactants in solution, pressure of gases, catalysts
90
State the effect of increasing the surface on the rate of a reaction
Increases the rate
91
Explain why increasing the surface area increases the rate of a reaction
More particles are available to collide, there are more frequent collisions between particles
92
State the effect of increasing the concentration on the rate of a reaction
Increases the rate
93
Explain why increasing the concentration increases the rate of a reaction
Higher concentration means there are more particles in the same volume, there are more frequent collisions between particles
94
State the effect of increasing the pressure on the rate of a reaction
Increases the rate
95
Explain why increasing the pressure increases the rate of reaction
Higher pressure means there are more particles in the same volume, there are more frequent collisions between particles
96
State the effect of increasing the temperature on the rate of reaction
Increases
97
What is activation energy?
The minimum amount of energy a particle needs before it will be able to react when it collides with other particles
98
Explain why increasing the temperature increases the rate of reaction
Increases the speed at which particles move therefore more frequent collisions. Increases the number of particles that have the activation energy therefore there are more successful collisions (more collisions result ina reaction)
99
What is a catalyst?
Something which speeds up the rate of reaction but is not used up in that reaction
100
How do catalysts speed up the rate of reaction?
They provide an alternative route for the reaction to take which has a lower activation energy
