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N5 Chemistry > Unit 1: Chemical Changes and Structure > Flashcards

Unit 1: Chemical Changes and Structure Flashcards

1
Q

4 signs of a chemical reaction

A

Effervescence, colour change, temperature change, precipitation

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2
Q

Reaction rate

A

How quickly a reaction progresses (how quickly the products are formed)

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3
Q

Ways to increase reaction rate

A

Increase temperature, increase concentration, decrease particle size, add a catalyst

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4
Q

Catalyst

A

A substance that speeds up a chemical reaction and can be retrieved chemically unchanged at the end of the reaction

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5
Q

On a graph, when reaction rate increases

A

The slope of the graph increases

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6
Q

On a graph, when the quantity of reactants increases

A

The height of the graph increases

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7
Q

Why is it useful to know the rate of a reaction?

A

Safety (e.g. medicines, preventing explosions), economy (how quickly a product can be made/sold)

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8
Q

Methods to measure gas produced in a reaction

A

Gas syringe, inverted measuring cylinder (if the gas is insoluble in water), mass loss over a balance

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9
Q

Average rate

A

Used to describe how quickly a reaction happens in a specific interval of time

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10
Q

Average rate formula

A

Change in quantity / change in time

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11
Q

Increasing temperature affects

A

The slope of the graph

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12
Q

Increasing concentration affects

A

The slope and the height of the graph if the reactant is not in excess

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13
Q

Decreasing particle size affects

A

The slope of the graph

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14
Q

Adding a catalyst affects

A

The slope of the graph

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15
Q

Excess

A

Excess reagents are reactants that are not used up when a reaction is finished

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16
Q

If a reactant is in excess…

A

Adding more will not affect the height of the graph (it will not produce more product)

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17
Q

Column in the periodic table

A

Group

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18
Q

Row in the periodic table

A

Period

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19
Q

Elements in the same group have

A

The same valency and similar chemical properties

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20
Q

Elements in the same period have

A

The same number of occupied electron shells

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21
Q

Group 1

A

Alkali metals

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22
Q

Group 7

A

Halogens

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23
Q

Group 8/0

A

Noble gases

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24
Q

Proton mass and charge

A

Mass of 1, charge of +1

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25
Neutron mass and charge
Mass of 1, charge of 0
26
Electron mass and charge
Mass of (almost) 0, charge of -1
27
Where are protons and neutrons found?
In the nucleus
28
Where are electrons found?
In the electron shells
29
Atoms have a neutral charge because
They have the same number of protons and electrons (+ and - charges cancel out)
30
Outermost electron shell
Valence shell
31
Electrons in the outermost shell
Valence electrons
32
Diatomic elements
Oxygen, hydrogen, nitrogen, bromine, fluorine, chlorine, iodine
33
Nuclide notation
Symbol in middle, top left = mass number, bottom left = atomic number, top right = charge
34
Why do electrons fill the smallest shell first?
The negative electrons are attracted to the positive nucleus
35
Max number of electrons in each shell
Shell 1: 2 Shell 2: 8 Shell 3: 8
36
Why are noble gases stable/unreactive?
Because they have full outer shells
37
Ion
A charged atom formed when an atom has gained or lost electrons
38
Why do atoms forms ions?
To gain a full outer shell, which makes them more stable
39
Metal and non metal atoms forming ions
Metal atoms form positive ions, non metal atoms form negative ions
40
Isotopes
Atoms with the same atomic number but different mass numbers
41
Relative atomic mass
The average mass of all isotopes of an element, taking into account their relative abundance
42
RAM formula
(Mass1 x %abunance) + (mass2 x %abundance) + ...
43
Covalent bond
The electrostatic attraction two positive nuclei have for a shared pair of electrons
44
Dot and cross diagrams
Show valence electrons in covalent bonds
45
Molecule shape of 2 atoms
Linear
46
Molecule shape of 3 atoms
Angular
47
Molecule shape of 4 atoms
Trigonal pyramidal
48
Molecule shape of 5 atoms
Tetrahedral
49
Shape of molecules containing boron
Trigonal planar (like a flat trigonal pyramidal)
50
Covalent molecular
Discrete (separate molecules), strong covalent bonds within the molecules, weak forces of attraction between molecules
51
Properties of covalent molecular substances
Low melting and boiling points, could be any state at room temperature (25 degrees celsius), some dissolve in water, the ones that don't likely dissolve in other solvents (e.g. Hexane)
52
Covalent network
Thousands of atoms bonded together
53
Properties of covalent network substances
High melting and boiling points, solid at room temp, do not dissolve, hard, durable, extremely unreactive
54
Do covalent substances conduct electricity?
No
55
Ionic lattice
Grid like arrangement held together by strong electrostatic attractions between positive and negative ions
56
Properties of ionic substances
High melting and boiling points, solid at room temp, often soluble, conduct electricity when molten or dissolved
57
Why do ionic substances conduct electricity when molten/dissolved?
Because ions can move freely
58
Best way to determine bonding type
Conductivity test
59
pH is determined by
The relative concentration of hydrogen and hydroxide ions
60
pH scale
Used to measure how acidic/alkaline a substance is
61
Acidic solutions have pH
<7
62
Neutral solutions have pH
=7
63
Alkaline solutions have pH
>7
64
Soluble non-metal oxides turn pH
Acidic
65
Soluble metal oxides turn pH
Alkaline
66
How do insoluble oxides affect pH?
They have no effect
67
Base
A substance that can neutralise an acid
68
Alkali
A soluble base
69
Neutralisation
A reaction between an acid and a base that produces a salt and a water
70
An acid produces
hydrogen ions
71
Alkalis produce
hydroxide ions
72
An acidic solution has
A higher concentration of hydrogen ions than hydroxide ions
73
An alkaline solution has
A higher concentration of hydroxide ions than hydrogen ions
74
A neutral solution has
Equal concentrations of hydrogen ions and hydroxide ions
75
Why can water conduct electricity despite being a covalent substance?
Because a small number of water molecules dissociate (break down) into ions
76
Around how many water molecules dissociate into ions?
Around 1 in 555 million
77
Dilution
Adding more of a solvent to a solution, decreases the concentration of hydrogen ions and hydroxide ions
78
For pH to change by 1...
A solution must be diluted tenfold
79
Soluble metal oxides react with water to produce
Metal hydroxides
80
Soluble non metal oxides react with water to produce
Acids
81
Do insoluble oxides react with water?
No
82
Salt
A substance that is produced when the hydrogen ions in an acid are replaced by metal ions (or NH4+)
83
Acid + metal oxide ---->
Salt + water
84
Acid + metal hydroxide ---->
Salt + water
85
Acid + metal carbonate ---->
Salt + water + carbon dioxide
86
Spectator ions
Ions that remain unchanged by a reaction
87
What is a trick used to identify the spectator ions in a reaction?
Spectator ions can usually be found in the aqueous product of a reaction
88
Acid-base titration
The unknown concentration of an acid or a base is determined by accurately measured the volumes used in a neutralisation reaction
89
What glassware must be used for titrations?
Burette and pipette (accurate glassware)
90
Why is an indicator used during titration?
To show the end point of neutralisation (which occurs at the first permanent colour change)
91
What is a common indicator used in acid-base titration?
Phenolphthalein (colourless in acidic/neutral solutions, pink in alkaline solutions)
92
Correct titration technique
Use a white tile to see end point Read measurements at eye level Read measurements at the bottom of the meniscus (curve) Do a rough titre first Repeat titres until you have concordant results (within 0.2cm3 of each other)
93
Concordant
Within 0.2cm3 of each other

N5 Chemistry (3 decks)

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