Definitions Flashcards
(158 cards)
1
Q
What is metallic bonding?
A
Metallic bonding is the electrostatic force of attraction between positively charged ions and negatively charged delocalised electrons.
2
Q
What are covalent bonds?
A
a shared pair of electrons electrostatically attracted to the positively charged nuclei of two non-metal elements.
3
Q
What is covalent radius?
A
the measure of how large and individual atom is.
4
Q
What is the first ionisation energy?
A
the energy involved in removing one mole of electrons from one mole of atoms in the gaseous state.
5
Q
What is the screening effect?
A
The inner energy levels screen the nuclear charge from the outer electrons.
6
Q
What is electronegativity?
A
Electronegativity is a measure of the attraction an atom involved in a bond has for the electrons of that bond.
7
Q
What are intermolecular bonds?
A
Bonds between molecules.
8
Q
What are intramolecular bonds?
A
Bonds inside/within molecules.
9
Q
What is a pure covalent bond?
A
The two atoms have the same electronegativity and have no ionic character at all. Examples include diatomic elements.
10
Q
What is a polar covalent bond?
A
When a shared pair of electrons are not shared equally. This is because one of the elements has a higher electronegativity than the other.
11
Q
What is a dipole?
A
When one side of the atom becomes slightly negatively charged and the other side becomes slightly positively charged.
12
Q
What are ionic bonds?
A
When there’s an uneven sharing of bonding electrons in covalent bonds. This is due to a large difference in electronegativity.
13
Q
What are London dispersion forces?
A
They are the weakest type of intermolecular bonds.
14
Q
How do London dispersion forces form?
A
They are caused by an uneven distribution of electrons within and atom making one side slightly negatively charged and the other slightly positively charged. This is known as an temporary dipole. The temporary dipole can move towards an atom causing an induced dipole which create London dispersion forces.
15
Q
What are permanent dipole to permanent dipole interactions?
A
They are when polar molecules display attractions between the oppositely charged ends of the molecule. This intermolecular force is stronger than London dispersion forces.
16
Q
What is Hydrogen bonding?
A
They occur when Hydrogen bonds with Oxygen, fluorine or nitrogen.
17
Q
When are polar covalent bonds polar molecules?
A
When the shape of the molecules is asymmentrical.
18
Q
When are polar covalent bonds non polar molecules?
A
When the shape of the molecule is symmetrical and the charges cancel each other out.
19
Q
What is viscosity and what affects how viscous a molecule is?
A
Viscosity is the thickness of a liquid and can be affected by the number of hydroxyl groups are present. the greater the number of hydroxyl groups present the more viscous the molecule is.
20
Q
What is solubility and what affects how soluble a molecule is?
A
Solubility is how much a substance will dissolve in a given volume of liquid. Polar molecules will dissolve in polar substances and non-polar molecules will dissolve in non-polar solvents. The number of hydroxyl groups present the more soluble the substance is. the greater the number of hydroxyl groups present, the more soluble the molecule.
21
Q
What is a reducing agent?
A
Found at the top right hand side of the data book. It loses electrons to another element (it is oxidised). Note: The strongest reducing agents are the alkali metals in group 1.
22
Q
What is an oxidising agent?
A
Found on the bottom left hand side of the data book. It gain electrons from other atoms (it is reduced).
23
Q
What is a redox reaction?
A
When both oxidation and reduction takes place.
24
Q
What are displacement reactions?
A
When metals higher in the electrochemical series displace lower metals from a solution in their ions
25
What does the collision theory state?
For a reaction occur the reactant must collide with the correct collision geometry and with enough energy to break existing bonds.
26
What is an activated complex?
An intermediate stage in which there is a high energy, unstable arrangement of atoms.
27
What are the factors affecting the rate of a reaction?
Temperature, concentration, pressure, particle size and the use of a catalyst.
28
What is activation energy?
Activation energy is the minimum energy required for the reaction to occur.
29
What happens to the activation energy when you add a catalyst?
Adding a catalyst lowers the activation energy causing the number of molecules with the minimum kinetic energy for the reaction to occur increase. This increases the number of successful collisions taking place.
30
What is enthalpy?
A measure of the chemical energy in a substance.
31
What is an exothermic reaction and what is it represented as?
When heat energy is released. The products will have less energy than the reactants because energy has been released. The enthalpy change for an exothermic reaction is always negative -
32
What is an endothermic reaction and what is it represented as?
What heat energy is absorbed. The products have more enthalpy than the reactants. The enthalpy change for an endothermic reaction is always positive +
33
What is the enthalpy of combustion?
The heat energy given out when one mole of a substance burn completely in oxygen. Always exothermic and are therefore negative.
34
What does Hess's Law state that?
The enthalpy change for a chemical reaction is independent of the route taken meaning the enthalpy change for the overall reaction will be identical regardless of the number of steps taken
35
What is bond enthalpy?
The energy required to break one mole of bonds in a diatomic molecule.
36
What is mean bond enthalpy.
The average energy required to break one mole of bonds for a bond that occurs in a number of compounds
37
When is a reaction in dynamic equilibrium?
When rate of the forward reaction is equal to the rate of the reverse reaction.
38
What does Le Chatelier's principle state?
If a system at equilibrium is subjected to any change, the system will adjust itself to counteract the applied change.
39
What happens when you increase the temperature of a equilibrium?
It favours the endothermic reaction.
40
What happens when you decrease the temperature of a equilibrium?
It favours the exothermic reaction.
41
What happens when you increase the pressure of a equilibrium?
It favours the side with the less gas volume.
42
What happens when you decrease the pressure of a equilibrium?
It favours the side with the greater gas volume.
43
What happens when the number of moles of gas are the same for equilibrium?
Because they have the same number of moles, changing the pressure does not favour either side of the equilibrium.
44
What does adding a catalyst do to the position of the equilibrium?
It has no effect on the position of the equilibrium- it does allow the equilibrium to be reached more quickly or at a lower temperature making the reaction more profitable.
45
What is a standard solution?
A solution of accurately known concentration.
46
What is the general formula for alkanes?
CnH2n+2
47
What is the general formula for alkenes?
CnH2n
48
What is the general formula for the cycloalkanes?
CnH2n
49
What is the general formula for alcohols?
CnH2n+1OH
50
What is the general formula for the carboxylic acids?
CnH2n+1COOH
51
What is molecular formula?
When only the number of atoms each element in one molecule of the substance.
52
What is full structural formula?
When all the atoms and all the bonds within molecules and shows exactly which is joined to which.
53
What is shortened structural formula?
Shows how the atoms are joined but only shows some, if any of the bonds.
54
What are addition reactions?
When the double bond of an alkene partially breaks when the reactant molecule attacks and adds on across.
55
What can be used to test for unsaturation and what is the reaction known as?
Bromine will rapidly decolourise alkenes. The addition of bromine is called bromination.
56
What are isomers?
Compounds with the same molecular formula but different structural formula.
57
What are alcohols?
Contain the hydroxyl functional group and the names end in ol.
58
What is a primary alcohol?
When the hydroxyl functional group is attached to a carbon atom with at least two hydrogen atoms attached.
59
What is a secondary alcohol?
When the hydroxyl group is attached to a carbon with only one hydrogen atom attached to it.
60
What is a tertiary alcohol?
When the hydroxyl group is attached to a carbon with no hydrogen atoms attached to it.
61
What is the name of an alcohol with two hydroxyl groups?
Diols
62
What is the name of an alcohol with three hydroxyl groups?
Triols
63
What do primary alcohols partially oxidise into?
Aldehydes (alkanals)
64
What do secondary alcohols oxidise into?
Ketones (alkanones)
65
What functional group do aldehydes and ketone have?
Carbonyl (C=O)
66
What do tertiary alcohols oxidise into?
They cannot oxidise.
67
What do primary alcohols fully oxidise into?
Carboxylic acids
68
What does oxidation do to the oxygen to hydrogen ratio?
It increases.
69
What does reduction do to the oxygen to hydrogen ratio?
It decreases.
70
What happens when carboxylic acids react with a base/alkali?
It forms a salt (soap) and water.
71
What happens when an aldehyde oxidises with acidified potassium dichromate?
The orange solution turns into a green/blue solution.
72
What happens when an aldehyde is oxidised with Fehling's (Benedict's) solution?
The blue solution turns into a orange precipitate.
73
What happens when an aldehyde is oxidised with Tollen's reagent.
The colourless solution will turn into a silver mirror.
74
What do esters consist of?
A carboxylic acid and an alcohol.
75
How do esters form?
By the condensation reaction between a alcohol and a carboxylic acid.
76
What is a condensation reaction?
When two molecules are joined together with the elimination of a small molecul.
77
What is a hydrolysis reaction?
When a molecule reacts with water to break down into smaller molecules.
78
What is an esters functional group?
-COO- known as an ester link.
79
How do fats and oils form?
By the condensation of glycerol and three fatty acid chains.
80
What is glycerol also known as?
Propane-1,2,3-triol
81
What are fatty acids?
A long carboxylic acid chain ranging from C4 to C28.
82
What are fats and oils also known as?
Triglycerides.
83
What is the low melting points of oil related to?
The higher degree of saturation meaning the molecules cannot pack closely together. This causes London dispersion forces to be weaker than in fat molecules less energy is required to separate the oil molecules.
84
How do you increase the melting point of an oil?
By the addition reactions between double bonds and hydrogen. This reduces unsaturation.
85
How are soaps made?
They are the salts made from the alkaline hydrolysis of fats and oils.
86
What does soap contain?
A hydrophilic (ionic charged) part which dissolves in water and a hydrophobic (non-polar) past which dissolves in the grease or oils.
87
What is produced when an ester is hydrolysed with an acid?
The carboxylic acid and the alcohol are produced.
88
What are emulsions?
Small droplets of one liquid dispersed in another.
89
What is the role of a emulsifier?
Allows small droplets of a liquid to remain suspended in another liquid. They prevent the liquids from separating two layers.
90
How are emulsifiers made?
By reacting edible oils in glycerol.
91
What structural properties are found in emulsifiers?
They have a non-polar hydrophobic part and a polar hydrophilic part.
92
How are proteins formed?
By condensation polymerisation when amino acid molecules join together and a water molecule is removed.
93
What is the functional groups for proteins?
Amide link (-CONH-)
94
What are condensation polymers?
Made from monomers with two functional groups per molecule. An example includes polyesters and polyamides.
95
What is a property of polyamides?
They are strong but lightweight. This is due to the hydrogen bonding which occurs between the polyamide chain.
96
What are essential fatty acids and amino acids?
They are fatty acids and amino acids that cannot be produced by the body and must be obtained from the diet.
97
What happens when fats and oils in food come into contact with oxygen/air?
They fats and oils in the food undergo oxidation reactions causing them to turn rancid.
98
What are essential oils?
Are compounds that can be extracted from plants and are used in perfume, cleaning products, cosmetic and flavouring in foods.
99
What do essential oils mainly consist of?
Terpenes which are made up of isoprene units.
100
What is the general formula for isoprene?
C5H8
101
What is produced during condensation polymerisation?
The product and water.
102
What happens to proteins during digestion?
The enzyme hydrolysis of the protein which produces amino acids.
103
What is sunblock?
It contains compounds such as titanium dioxide that reflects UV so it does not reach the skin at all.
104
What is sunscreen?
It contains compounds that filter the UV light so that less UV reaches the skin.
105
What are free radicals?
They are highly reactive atoms that have one unpaired electron and are formed when a covalent bond in an atom is broken by UV.
106
What is the initiation step?
When the UV breaks some CL-CL bonds and for two chlorine free radical.
107
What is the propagation step?
The highly reactive chlorine free radical react with hydrogen molecules. This produces hydrogen free radicals that can react with chlorine atoms.
108
What is the termination step?
When two free radicals react together to form a stable molecule.
109
What are free radical scavengers?
They are chemicals that react with and destroy free radicals. This prevents the chain reaction from occurring.
110
What is the other name for isoprene?
2-methylbuta-1,3-diene
111
What is hard water?
Water containing high levels of dissolved metal ions.
112
What does hard water form when mixed with soap?
Scum (insoluble precipitate)
113
What is hydrogen peroxide H2O2?
An oxidising agent
114
What is dichromate and permanganate ions?
Strong oxidising agents in acidic solution
115
What is carbon monoxide CO?
A reducing agent
116
What happens with hydrogen bonding in ice?
The density of ice become less than water at lower temperatures.
117
What does a metal oxide reacting with a carboxylic acid form?
A salt and water
118
What does a metal hydroxide reacting with a carboxylic acid form?
A salt and water
119
What does a metal carbonate reacting with a carboxylic acid form?
A salt, water and carbon dioxide
120
What are antioxidants?
Molecules that prevent unwanted oxidation reactions and can easily be oxidised.
121
What is a filtration reaction used for?
To separate solid residue from a liquid or solution.
122
What is distillation used for?
Used to separate mixtures of liquids or to burn off the liquid component of a mixture.
123
What is a condenser used for?
To prevent reactants and products from escaping the reaction vessel in gas form.
124
What are the steps of weighing by difference?
1. Measure the mass of the empty vessel
2. Use a spatula to measure out the solid
3. Take a note of the mass of vessel and solid and work out take away mass of vessel and mass to reactant added to calculate the total mass of solid added (accurately approximately)
4. Transfer solid to beaker but do not rinse the vessel
5. Reweigh the vessel and take away the mass of solid and vessel from the weight of the vessel at the end to find the mass of solid transferred to beaker
125
What are the steps of producing a standard solution?
1. Weigh the mass of substance required (weigh by difference).
2. Dissolve the substance in a small amount of deionised water and transfer to the volumetric flask
3. Rinse beaker and stirring rods to ensure all of the sodium carbonate is transferred into the beaker.
4. Fill the flask up to the mark with deionised water until the bottom of the meniscus reaches the line.
126
What is affected by Hydrogen bonding?
Boiling points, melting points, viscosity and solubility.
127
What can oxidising agents do with reference to bacteria?
They kill fungi, bacteria and inactivated viruses.
128
What does solubility, boiling point and volatility depend on?
- The presence of hydrogen bonds
- The arrangement of polar covalent bonds which result in a molecule having a permanent dipole
- Molecular size which could affect LDF
- The polarities of solute and solvent
129
What is the systematic name for isoprene?
2-methylbuta-1,3-diene
130
What is the general formula for terpenes?
(C5H8)n
131
What is molar volume?
The volume occupied by one mole of any gas at a certain temperature and pressure.
132
What is percentage yield?
The percentage yield is a simple way of comparing the amount of product actually obtained from a reaction with the amount expected.
133
What happens if the percentage yield is 100%?
Then all of the atoms in the reactants will be converted into products.
134
What is atom economy?
The atom economy of a chemical reaction is a measure of the percentage of reactants that become useful products
135
Why is an indicator not required in a reaction with acidified permanganate?
Purple permanganate solution turns colourless when reduced.
136
What does chromatography do?
It separates substances by using the differences in polarity or molecular size.
137
What is a titration reaction?
Used to determine accurately the volume of solution required to reach the end point of a reaction.
138
What is an indicator used for?
To show when an end point has been reached.
139
What are filter funnels/filter paper used for?
To separate solids from liquids.
140
What is an evaporating basin used for?
To heat water and evaporate it off a salt solution.
141
What is a delivery tube used for?
To deliver gas from a reaction and the gas is usually bubbled through water.
142
What is a thermometer used for?
To measure the temperature of chemicals.
143
What are droppers used for?
To transfer small volumes of liquid.
144
What is a beaker used for?
To hold liquids and have a non accurate scale on the side and shouldn't be used to measure.
145
What is a test tube for?
to carry out small scale reactions/boiling tubes are used to heat up reactions in a water bath.
146
What is a conical flask used for?
Used in titrations and filtering and have a non accurate scale on the side.
147
What is a measuring cylinder used for?
Used to measure liquid and have a scale on side.
148
What is a burette used for?
Used in titration reactions and have a very accurate scale and have a tap at the bottom to allow liquid to flow.
149
What is a pipette used for?
It only measures one set volume of liquid shown with a mark on neck. Filled using a safety filler.
150
What is a standard/volumetric flask used for?
To measure one volume of liquid and used to make standard solutions with a known concentration. Volume is shown by using a line of the neck.
151
What is a heating plate used for?
An electronic way of heating up liquids and used to heat flammable liquids.
152
What is a Bunsen burner?
Heats substances using flames and should not be used on flammable substances.
153
What is volatility?
How easy a substance will evaporate/turn into a gas.
154
What is the relationship between volatility and large molecular mass/strong intermolecular forces?
A molecule with a large molecular mass or strong intermolecular forces will be less volatile.
155
What is the relationship between volatility and small molecular mass/weak intermolecular forces?
A molecule with a small molecular mass or weak intermolecular forces will be more volatile.
156
What are homogeneous catalysts?
Catalysts in the same physical state as the reactants.
157
What are heterogeneous catalysts?
Catalysts in a different physical state from the reactants.
158
What glucose an example of and what substance does it affect?
It is a reducing sugar and reduces copper(II) ions to copper(I) ions by undergoing oxidation.
