IGCSE Chemistry - Pearson Edexcel - GLOSSARY DEFINITIONS ONLY - COMPLETED Flashcards
FLASHCARDS MADE MYSELF WITH AID OF SOURCE BOOK: CHEMISTRY PEARSON EDEXCEL INTERNATIONAL GCSE (9-1) STUDENT BOOK BY JIM CLARK, STEVE OWEN AND RACHEL YU
1
Q
What does absorb mean?
A
Take in (a gas or a liquid).
2
Q
What is an acid?
A
A substance that acts as a source of hydrogen ions (H+) in solution (Arrhenius theory) or as a proton donor (Brønsted–Lowry theory).
3
Q
What is acid rain?
A
Rain which has a pH of less than about 5.6. It is caused when water and oxygen in the atmosphere react with sulfur dioxide to produce sulfuric acid, or with various oxides of nitrogen (NO(x)) to give nitric acid.
4
Q
What is activation energy?
A
The minimum amount of energy required for a collision to be successful, i.e. to result in a reaction.
5
Q
What is an addition reaction?
A
A chemical reaction in which one molecule adds to another without taking anything away, to form a single product. For example, when alkenes react with halogens, the halogen atoms add onto the alkene molecule.
6
Q
What is addition polymerisation?
A
Polymerisation of monomers containing a carbon-carbon double bond. A large number of monomer molecules add onto each other without anything else being formed.
7
Q
What are alcohols?
A
A homologous series of compounds which all contain an -OH functional group attached to a hydrocarbon chain.
8
Q
What are alkali metals?
A
Group 1 elements including lithium, sodium, potassium, rubidium, caesium and francium. NOTE: HYDROGEN IS NOT AN ALKALI METAL.
9
Q
What are alkanes?
A
A homologous series of similar hydrocarbons in which all the carbons are joined to each other with single covalent bonds. These are saturated compounds with the general formula CnH2n+2.
9
Q
What are alkanes?
A
A homologous series of similar hydrocarbons in which all the carbons are joined to each other with single covalent bonds. These are saturated compounds with the general formula CnH2n+2.
10
Q
What are alkenes?
A
A homologous series of hydrocarbons which contain a carbon-carbon double bond. These are unsaturated compounds with the general formula CnH2n.
11
Q
What are allotropes?
A
Different forms of the same element, for example diamond, graphite and C60 fullerene are three allotropes of carbon.
12
Q
What is an alloy?
A
A mixture of metal with, usually, other metals or carbon. For example, brass is an alloy of copper and zinc, and steel is an alloy of iron and carbon.
13
Q
What are amphoteric substances?
A
Substances that can react with both acids and bases to form salts.
14
Q
What does anaerobic mean?
A
In the absence of air.
15
Q
What does anhydrous mean?
A
Without water.
16
Q
What is an anion?
A
A negative ion, formed by atoms gaining electrons.
17
Q
What is the anode?
A
The positive electrode in electrolysis (Positive Anode Negative Is Cathode - PANIC) which attracts negative ions (anions).
18
Q
What is an anomalous result?
A
A result that does not fit in with the pattern of the others.
19
Q
What does aqueous mean?
A
Dissolved in water.
20
Q
What is an array?
A
An ordered arrangement of things.
21
Q
What is ash?
A
The soft powder that remains after something has been burned.
22
Q
What is an atom?
A
The smallest piece of an element that can still be recognised as that element.
23
Q
What is the atomic number of an atom?
A
The number of protons in an atom (also equal to the number of electrons in an atom).
24
What is Avogadro's constant?
CONTEXT: 1 mol is the amount of substance that contains the same number of particles as there are atoms in 12.0 g of carbon-12.
ANSWER: Avogadro's constant is the number of ^12C atoms in 12g of ^12C(6.02 x 10^23 mol^-1).
25
What is balancing an equation?
A process of putting coefficients in front of formulae so that the same number of atoms of each type is on both side of the equation.
26
What is the barrier method?
A method of rust prevention by coating iron with paint, oil, grease or plastic, so that oxygen/water cannot reach the iron/steel.
27
What is a base?
A substance that neutralises acids by combining with the hydrogen ions in them. They are usually metal oxides, hydroxides or ammonia. A soluble base is called an alkali, and it is a substance that acts as a source of hydroxide ions (OH-) in solution (Arrhenius theory) or as a proton acceptor (Brønsted–Lowry theory).
28
What is a batch?
A group of things that are produced or are dealt with together.
29
What is a biofuel?
A fuel that is made from biological sources, such as sugar cane or corn.
30
What is a biopolyester?
A polyester which is biodegradable.
31
What is bleach?
A chemical used to make something paler or whiter, or to sterilise something.
32
What is boiling?
The change of state from a liquid to a gas. It occurs at the boiling point.
33
What is bond energy?
The amount of energy required to break 1 mole of covalent bonds in gaseous molecules, or the amount of energy released when 1 mole of covalent bonds are formed in gaseous molecules.
34
What is a branch?
Something that grows out from the main part of an object.
35
What is bubbling?
Producing bubbles.
36
What is a bulb?
A glass object that produces light when electricity is passed through it. OR, the wider part of some plastic pipettes, which is squeezed to allow the pipette to be filled.
37
What is calorimetry?
Measuring the heat given out or taken in by a chemical reaction.
38
What are carboxylic acids?
A homologous series of compounds which all contain
a -COOH functional group attached to a hydrocarbon chain.
39
What is a catalyst?
A substance that speeds up a chemical reaction by providing an alternative pathway of lower activation energy. Catalysts are not used up and remain chemically unchanged at the end of the reaction.
40
What is a catalytic converter?
A device used in cars to convert oxides of nitrogen and carbon monoxide into harmless nitrogen gas and carbon dioxide. It uses platinum, palladium and rhodium as catalysts.
41
What is the cathode?
The negative electrode (Positive Anode Negative Is Cathode - PANIC) in electrolysis, which attracts positive ions (cations).
42
What is a cation?
A positive ion, formed by atoms losing electrons.
43
What are 'chemical means'?
Methods which involve chemical reactions.
44
What is a chromatogram?
The absorbent paper from paper chromatography showing the separation of different coloured substances.
45
What is a clump?
A small group or cluster.
46
What is the coefficient?
The number written in front of formulae in a balanced chemical equation.
47
What is a coil?
A continuous series of circular rings into which something such as a wire or rope has been wound or twisted.
48
What is collision theory?
Collision theory states that for a reaction to occur, the reactant particles must collide with each other and the collision needs to have sufficient energy and the correct orientation.
49
What is combustion?
A chemical reaction in which a substance reacts with oxygen (burns) to form products and heat.
50
What is a competition reaction?
A displacement reaction between a more reactive metal and the oxide of a less reactive metal.
51
What is complete combustion?
Complete combustion occurs when a hydrocarbon burns in sufficient oxygen (burns) and forms carbon dioxide and water as products.
52
What is a compound?
A substance that forms when two or more elements chemically combine. The elements cannot be separated by physical means.
53
What is condensation?
The change of state from a gas to a liquid. It occurs at the condensation point.
54
What is condensation polymerisation?
Polymerisation of monomers in which each time two monomers combine, a small molecule such as water or hydrogen chloride is removed.
55
What is a corrosive substance?
A substance which can damage living tissue.
56
What is covalent bonding?
Strong electrostatic forces of attraction between the nuclei of the atoms making up the bond and the shared pair of electrons.
57
What is cracking?
A process in which long-chain alkanes are converted to alkenes and shorter-chain alkanes. It is carried out using silica or alumina as catalyst at a temperature of 600 - 700°C.
58
What is crude oil?
Formed from the remains of living organisms when their soft tissue was gradually changed by high pressure and high temperatures into a thick, black oil. Crude oil is a mixture of hydrocarbons.
59
What is crystallisation?
A process in which a solute (soluble solid) is obtained from its solvent.
60
What does damp mean?
Slightly wet.
61
What is a decomposition reaction?
A chemical reaction in which a compound is broken down into its elements or simpler compounds.
62
What does dehydration mean?
Removal of water.
63
What are delocalised electrons?
Electrons that are no longer attached to particular atoms or pairs of atoms, but are free to move throughout the whole structure.
64
What is a denatured enzyme?
An enzyme which has lost its function due to structural changes, usually caused by changes in temperature pH.
65
What is the dependant variable?
What you measure in an experiment.
66
What is deposition?
The change of state directly from a gas to solid.
67
What is a diatomic molecule?
A molecule that contains two atoms.
68
What is a condensation reaction?
A chemical reaction in which two molecules combine to form a larger molecule with elimination of a small molecule such as water.
68
What is diffusion?
The random movement of particles from an area of high concentration to an area of low concentration.
69
What does dimerise mean?
Forming a dimer - two identical molecules react to form a larger molecule.
70
What does dip mean?
To put something into a liquid and lift it out again.
71
What is a discharged ion?
An ion which loses its charge by losing or gaining electrons.
72
What is a displacement reaction?
A chemical reaction in which a more reactive element replaces a less reactive one in its compound.
73
What is a displayed formula?
A formula that shows all the bonds in a molecule as individual lines. Each line represents a pair of shared electrons in a covalent bond.
74
What is a dot-and-cross diagram?
A representation of how electrons are arranged in ions or molecules.
75
What is a double bond?
A double bond is where atoms share two pairs of electrons in a covalent bond.
76
What does drive off mean?
Force something to go away.
77
What is dry ice?
Solid carbon dioxide.
78
What does it mean to say metal is ductile?
Ductile is a property of metal which allows it to be drawn out into wires.
79
What is a dynamic equilibrium?
Equilibrium means the concentrations of the reactants and the products in a reversible reaction remain constant. Dynamic means the reactions are still continuing, but the rate of forward reaction is equal to the rate of the reverse reaction.
80
What is an electrode?
A conductor through which electricity is passed into and out of an electrolyte.
81
What is electrolysis?
The chemical change caused by passing an electric current through a compound that is either molten or in solution.
82
What is electrolyte?
A liquid that undergoes electrolysis. Electrolytes are molten ionic compounds or solutions containing ions.
83
What is an electrolytic cell?
A compartment in which electrolysis occurs.
84
What is an electron?
A subatomic particle found in shells (energy levels) outside the nucleus of an atom. It has a relative mass of 1/1836 and a relative charge of 1-. For a neutral atom, the number of electrons = number of protons = the atomic number.
85
What is electronic configuration?
How electrons are arranged in the shells (energy levels) of an atom.
86
What is electrostatic attraction?
The force of attraction between something that is positive and something that is negative.
87
What is an element?
A substance that cannot be split into anything simpler by chemical means. An element contains atoms of the same atomic number.
88
What does the empirical formula of an atom give?
The empirical formula gives the simplest whole number ratio of the atoms present in a compound. It can be worked out from experimental data.
89
What is the end point of titration?
The point at which the indicator changes colour.
90
What are endothermic reactions?
Reactions in which heat energy is taken in from the surroundings.
91
What is energetics?
The study of energy change in chemical reactions.
92
What is enthalpy change?
The amount of heat energy taken in or given out in a chemical reaction. It has the symbol ΔH.
93
What are enzymes?
Biological catalysts, usually consisting of proteins.
94
What are esters?
Esters are organic compounds formed by the reaction of an alcohol with a carboxylic acid. They have the functional group -COO-.
95
What is esterification?
A chemical reaction in which an alcohol and a carboxylic acid react together to form an ester.
96
What is evaporation?
The change of state from a liquid to a vapour. It occurs at a temperature below the boiling point and only at the surface of the liquid.
97
What is excess?
Having more than enough of a reactant to react with all of something else.
98
What are exothermic reactions?
Reactions in which heat energy is given out to the surroundings.
99
What does fade mean?
To lose colour and brightness.
100
What is fermentation?
Converting sugar such as glucose into ethanol and carbon dioxide using enzymes in yeasts.
101
What is the filtrate?
The liquid that comes through the filter paper during filtration.
102
What is filtration?
A process to separate an insoluble solid from a liquid.
103
What does fizz mean?
To make many bubbles, producing a continuous sound.
104
What does flake off mean?
Come off in small pieces.
105
What does flash mean?
Shine suddenly and brightly for a short period of time.
106
What does flush out mean?
Force something out.
107
What is a formula?
A representation of a chemical showing the elements present.
108
What is a forward reaction?
A reaction from reactants to products (the left-to-right reaction).
109
What are fossil fuels?
Fossil fuels include coal, gas and fuels derived from crude oil, which all come from things that were once alive.
110
What is fractional distillation?
A process to separate two liquids of similar boiling points, for example ethanol and water or the components of crude oil.
111
What is a fractionating column?
A piece of equipment used for separating vapours in fractional distillation.
112
What is freezing?
The change of state from a liquid to a solid. It occurs at the freezing point.
113
What is the freezing point?
The temperature at which a substance changes its state from a liquid to a solid.
114
What is a fuel?
A substance that when burned in oxygen releases heat energy.
115
What is a fume?
A strong-smelling gas or smoke that is unpleasant to breathe in.
116
What is a functional group?
An atom or group of atoms that determine the chemical properties of a compound.
117
What is galvanisation?
A method of preventing rusting by coating iron with a layer of zinc.
118
What is a general formula?
A formula applicable to all members of a homologous series, for example CnH2n+2 for alkanes and CnH2n for alkenes.
119
What is a giant?
A structure in which there are no individual molecules and the bonding extends in all directions. There is no limit to the number of particles present.
120
What is a giant ionic lattice?
The arrangement of ions in an ionic compound in its solid state.
121
What is a girder?
A strong beam, made of iron or steel, that supports a floor, roof or bridge.
122
What is global warming?
Greenhouse gases, including carbon dioxide, trap the heat radiated from the Earth's surface (originally from the Sun) and lead to an increase in the temperature of the Earth and its atmosphere.
123
What does glow mean?
To produce a steady light.
124
What are greenhouse gases?
Gases such as carbon dioxide which can trap heat radiated from the Earth's surface (originally from the Sun).
125
What is a group?
A vertical column in the Periodic Table. All elements in the same group have the same number of outer shell electrons.
126
What is a half-equation?
A balanced symbol equation to describe either oxidation or reduction.
127
What is a halogen?
A group 7 element - includes fluorine, chlorine, bromine, iodine and astatine.
128
What does hammered mean?
Been hit with a hammer to be forced into a particular shape.
129
What is a homologous series?
A series of compounds with similar chemical properties because they have the same functional group. Each member differs from the next by -CH2-. The members show a gradation in physical properties.
130
What does hydrated mean?
Containing water.
131
What is hydration?
The adding of water molecules to an unsaturated molecule, for example converting ethene to ethanol.
132
What are hydrocarbons?
Molecules containing carbon and hydrogen only.
133
What is a hydrogen bond?
A special type of intermolecular force found between water molecules and in some other substances.
134
What is a hydrogen halide?
A compound formed between hydrogen and a halogen, with the formula HX where X stands for a halogen atom.
135
What is hydrogenation?
The addition of hydrogen molecules to an unsaturated molecule, for example converting ethene to ethane.
136
What is a hydroxium ion?
An ion formed when water accepts a proton from an acid. It has the formula H30+.
137
What is incomplete combustion?
Combustion which occurs when a hydrocarbon burns in insufficient oxygen. Water is still formed as a product, but carbon monoxide or carbon are formed instead of carbon dioxide.
138
What is the independent variable?
What you change/vary in an experiment.
139
What is an indicator?
A substance that has different colours depending on the pH.
140
What does inert mean?
Unreactive
141
What are intermolecular forces?
Forces of attraction between covalent molecules - they are much weaker than the covalent bonds within the molecules.
142
What is an ion?
A charged particle formed when an atom (or group of atoms) loses or gains electrons.
143
What is ionic bonding?
Strong electrostatic force of attraction between oppositely charged ions, formed by the transfer of electrons from one atom to another.
144
What does ionise mean?
To become an ion. Usually refers to losing electrons to become a positive ion.
145
What are iron filings?
Small pieces of iron that are used in some chemical experiments.
146
What does isoelectronic mean?
Having the same number of electrons.
147
What are isotopes?
Different atoms of the same element, with the same number of protons but a different number of neutrons. Isotopes have the same chemical properties.
148
What is kinetic energy?
A form of energy a substance possesses due to motion.
149
What is a lattice?
A regular array of particles.
150
What is a Liebig condenser?
A piece of equipment used to condense gas to liquid in distillation.
151
What is a litre?
A unit for volume. One litre = one dm^3.
152
What does malleable mean?
Malleability is a property of metal which allows it to be hammered into different shapes.
153
What is the mass number?
The total number of protons and neutrons in the nucleus of an atom.
154
What is melting?
The change of state from a solid to a liquid. It occurs at the melting point.
155
What is the melting point?
The temperature at which a substance changes its state from solid to liquid. A pure substance has a fixed melting point but a mixture may melt over a range of temperatures.
156
What is metallic bonding?
Electrostatic force of attraction between a lattice of positive ions and the sea of delocalised electrons.
157
What is microbial oxidation?
Oxidation by oxygen in the air in the presence of microorganisms such as bacteria and yeast.
158
What are minerals?
Naturally occurring, crystalline compounds in the Earth's crust.
159
What are miscible liquids (or gases)?
Liquids (or gases) which can mix with each other and form a homogenous mixture.
160
What is a mixture?
Two or more substances not chemically combined that can be separated by physical means.
161
What is molar enthalpy change?
The change in enthalpy when one mole of a particular reactant reacts.
162
What is a litre?
A unit for volume. One litre = one dm^3.
163
What is molar mass?
The mass of one mole of a substance.
164
What is a lump?
A mass of solid without a particular shape.
165
What is molar volume?
The volume occupied by one mole of a gas.
166
What is a mole?
A unit of the amount of a substance. A mole of anything contains the same number of particles as there are carbon atoms in 12g of carbon-12 (ie. 6.02 x 10^23 particles).
167
What is the molecular formula?
The molecular formula shows the actual number of each type of atom present in a molecule (covalent compound) or formula unit (ionic compound).
168
What is a molecule?
Two or more atoms covalently bonded together. Molecules contain a certain fixed number of atoms.
169
What is the molten state?
The liquid state when a solid has melted.
170
What are monomers?
Molecules which can join up to form a polymer.
171
What is mono-substitution?
A substitution reaction in which only one hydrogen atom in an alkane is replaced by a halogen atom.
172
What are native metals?
Metals which exist naturally as the uncombined element.
173
What is a neutralisation reaction?
A chemical reaction in which acids react with bases or alkalis to produce salts.
174
What is a neutron?
A subatomic particle in the nucleus of an atom. It has a relative mass of 1 and a charge of 0. The number of neutrons in an atom is equal to the mass number - the atomic number.
175
What are noble gases?
Group 0 elements, including helium, neon, argon, krypton, xenon and radon.
176
What does non-biodegradable mean?
Cannot be broken down by bacteria or fungi in the environment.
177
What is a non-continuous variable?
An independent variable which can only take certain values.
178
What is a non-renewable resource?
A finite resource that cannot be replaced, at least not for millions of years.
179
What is the nucleon number the same as?
The mass number.
180
What does the nucleus of an atom contain?
Contains protons and neutrons in an atom.
181
What is the octet rule?
The octet rule states that atoms generally lose, gain or share electrons in order to have eight electrons in their outer shell.
182
What are ores?
Rocks that contain enough of the mineral for it to be worthwhile to extract the metal.
183
What is organic chemistry?
A branch of chemistry that studies the compounds of carbon except for the very simplest (like carbon dioxide, carbon monoxide, the carbonates and the hydrogencarbonates).
184
What is oxidation?
The gain of oxygen or the loss of electrons.
185
What is an oxidising agent?
Something that oxidises something else by taking electrons away from it. An oxidising agent is reduced in a chemical reaction.
186
What is paper chromatography?
A process to separate a mixture of coloured substances using adsorbent paper.
187
What is the parent acid?
The acid from which a salt is formed, for example sulfuric acid is the parent acid for sulfates.
188
What is a particle?
A small object. In chemistry, 'particle' can be used to refer to atoms, molecules, ions or the subatomic particles, including protons, neutrons and electrons.
189
What is a period?
A horizontal row in the Periodic Table. All elements in the same period have the same number of occupied shells.
190
What is the Periodic Table?
A table in which elements are arranged in the order of increasing atomic number and in terms of chemical and physical properties.
191
What is the pH scale?
A scale to measure how acidic or how alkaline a solution is.
192
What are physical means?
Methods which involve changing temperature, dissolving etc., for separating components of a mixture (for example distillation, filtration, use of a magnet, chromatography or crystallisation).
193
What is plotting a graph?
Drawing a graph to represent information.
194
What is a plunger?
A part of a syringe that moves in and out.
195
What is a polar covalent bond?
A polar covalent bond is one in which electrons are not equally distributed between the two atoms.
196
What is a polymer?
A large molecule made when many small molecules (monomers) join together. It consists of many repeating units.
197
What is polymerisation?
The joining up of lots of small molecules (monomers) to make one big molecule (polymer).
198
What is a pop?
A sudden short sound, often loud.
199
What is the position of equilibrium?
A reference to the proportion of the various things in an equilibrium mixture. If the position of equilibrium of a reaction lies towards to the right, the equilibrium mixture contains a higher proportion of products than reactants.
200
What is pouring?
Making something flow out of a container by holding it at an angle.
201
What is precipitate?
A fine solid that is formed by a chemical reaction involving liquids or gases.
202
What is a precipitation reaction?
A chemical reaction in which a fine solid is formed from liquids or gases.
203
What is pressure?
The force acting on something per unit area. Pressure has the SI unit of Pa (N/m^2) and is caused by molecules hitting the walls of their container.
204
What is a proton?
A subatomic particle in the nucleus of an atom. It has a relative mass of 1 and a relative charge of 1+. The number of protons in an atom is equal to the atomic number.
205
What is the proton number the same as?
The atomic number.
206
What is quicklime?
Calcium oxide
207
What does radioactive mean?
Having an unstable nucleus that will emit particles and waves to achieve a more stable nucleus.
208
What is range in chemistry?
A number of things that are all of the same general type, or the extent of a variable or series.
209
What is the rate?
The speed at which the amount of reactants decreases or the amount of products increases. It is measured as a change in the concentration (or amount) of reactants or products per unit time.
210
What is the reactivity series?
A list of elements (mainly metals) in order of decreasing reactivity.
211
What is redox?
Reduction and oxidation. A redox reaction involves both reduction and oxidation occurring together.
212
What is a reducing agent?
Something that reduces something else by giving electrons to it. A reducing agent is oxidised in a chemical reaction.
213
What is reduction?
The loss of oxygen or gain of electrons.
214
What are refinery gases?
A mixture of methane, ethane, propane and butane. This mixture is commonly used as liquefied petroleum gas (LPG) for domestic heating and cooking.
215
What is the relative atomic mass?
The weighted average mass of the isotopes of the element, relative to the mass of 1/12th of a carbon-12 atom.
216
What is the relative formula mass?
The weighted average mass of a formula unit of a compound, relative to the mass of 1/12th of a carbon-12 atom. It is sometimes called relative molecular mass, when it refers to covalent molecules.
217
What is the relative isotopic mass?
The mass of one particular isotope of the element, relative to the mass of 1/12th of a carbon-12 atom.
218
What is the repeat unit?
The basic unit which repeats itself in a chain to form a polymer.
219
What is residue?
The solid left on the filter paper during filtration.
220
What direction is a reverse reaction?
From products to reactants (the right-to-left reaction).
221
What is a reversible reaction?
A reversible reaction is one that can go both ways - in other words, reactants react to form products and products can react to form reactants.
222
What is the RF value?
The retardation factor. This is calculated as the distance moved by a spot (from the pencil line) divided by the distance moved by the solvent front (from the pencil line) on a chromatogram.
223
What is roasting?
A process in which metal ores are heated in air to convert them into metal oxides.
224
What is rust?
The corrosion of iron in the presence of water and oxygen. The rust formed has the formula Fe↓2O↓3.xH↓2O, where x is a variable number, and can be called hydrated iron (III) oxide.
225
What is sacrificial protection?
A method of preventing rusting by attaching a block of a more reactive metal to iron. The more reactive metals undergo oxidation in preference to the iron.
226
What is salt?
A compound formed when a hydrogen is replaced by a metal or ammonium in an acid.
227
What is a saturated compound?
A compound containing only carbon-carbon single bonds with no carbon-carbon double or triple bonds.
228
What is a saturated solution?
A solution that contains as much dissolved solid as possible at a particular temperature.
229
What does 'scale up' mean?
Make larger.
230
What is scrubbing?
Removing pollutant gases from the gases produced in a combustion reaction.
231
What is a set up?
The way that something is organised or arranged. This can refer particularly to chemical apparatus.
232
What are the shells in an atom?
A series of levels where electrons are found outside the nucleus. Shells are also called energy levels. Each shell can hold a certain number of electrons.
233
What does 'shielded'/'screened' mean in relevance to the electrostatic forces of attraction acting on an electron?
'Shielded'/'screened' is a term used to describe how the electrostatic force of attraction on an electron from the nucleus is offset by inner shell electrons. The inner electrons shield the outer electrons from the full attraction of the nucleus.
234
What does 'shift' mean?
To move from one place to another.
235
What is simple distillation?
A process used to separate two liquids of different boiling points, or to separate the solvent and solid solute from a solution.
236
What is slaked lime?
Calcium hydroxide
237
What does 'soak' mean?
Make very wet.
238
What is solubility?
The mass of solute which must dissolve in 100g of solvent to form a saturated solution at a particular temperature.
239
What is the solubility curve?
A graph showing how the solubility of a solute in a particular solvent changes with temperature.
240
What is a solute?
The substance that dissolves in a solvent.
241
What is a solution?
The mixture formed when a solute dissolves in a solvent.
242
What is a solvent?
The liquid that a solute dissolves in.
243
What is soot?
A black powder consisting largely of carbon.
244
What are sparks?
Very small pieces of burning metal produced in a fire or by hitting and rubbing two hard objects together that leads to a sudden discharge of light.
245
What is specific heat capacity?
The amount of heat needed to raise the temperature of 1g of a substance by 1 °C.
246
What is specific heat capacity?
The amount of heat needed to raise the temperature of 1g of a substance by 1
247
What is a spectator ion?
An ion that is not changed in a chemical reaction. It is omitted from both the reactant and the product sides when writing ionic equations.
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What does 'spit' mean?
To send out small pieces of something, for example from a fire.
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What is stability in terms of reactions?
Stability is a term used to describe the relative energies of the reactants and the products in a chemical reaction. The more energy a chemical has, the less stable it is.
250
What is a straight chain?
A molecule with no branches in its molecular structure.
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What is the structural formula?
A formula that shows how the atoms are joined together in a molecule. It is often written in a condensed form by omitting all the carbon-carbon and carbon-hydrogen single bonds.
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What is structural isomerism?
The existence of two or more different structures with the same molecular formula.
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What are structural isomers?
Molecules with the same molecular formula, but different structural formulae.
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What is sublimation?
The change of state from a solid to a gas.
255
What is subscript?
A number or symbol written below the line.
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What is substitution?
A chemical reaction in which an atom or group of atoms in a molecule is replaced by a different atom or group of atoms. For example, when alkanes react with halogens in the presence of ultraviolent light, the hydrogen atoms in the alkanes are replaced by halogen atoms.
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What are successful collisions?
Collisions with energy greater than or equal to the activation energy. These collisions result in reactions.
258
What is a tangent?
A straight line that touches a curve, but does not cut across it.
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What does 'tarnish' mean?
To become dull and lose colour.
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What is thermal decomposition?
A decomposition reaction that requires heating to occur.
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What is titration?
A technique used to follow the course of a neutralisation reaction between an acid and an alkali. It can be used to find out how much of an acid/alkali reacts with a certain volume of an alkali/acid.
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What is a trace?
A very small quantity.
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What does 'trickle' mean?
Flow slowly in drops or in a thin stream.
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What is a triple bond?
Atoms sharing three pairs of electrons in a covalent bond.
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What is ultraviolet radiation (UV light)?
The part of the electromagnetic radiation spectrum that has wavelengths between those of visible light and X-rays. It is invisible to the human eye.
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What does 'undergo' mean?
To experience something.
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What are unsaturated compounds?
Compounds that contain one or more carbon-carbon double or triple bonds.
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What are vapours?
Gases that are produced when a liquid is heated.
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What does it mean to say something reacts 'vigorously'?
If something reacts vigorously, it does so rapidly and with energy.
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What is vinegar?
A dilute solution of ethanoic acid in water.
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What is a viscous liquid?
A liquid that is resistant to flow.
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What is a volatile substance?
A substance that evaporates easily.
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What does 'waft' mean?
Move gently through the air.
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What is water of crystallisation?
Water molecules that are part of a crystal structure in which they are chemically bound up with a salt. They are represented by .nH↓2O in the formulae of compounds, for example CuSO↓4.5H↓2O means there are five water molecules associated with each CuSO↓4 unit.
275
What is a weighted average?
An average which takes into account the percentage abundance of the components.
276
What is a wick?
The piece of thread/string in a candle, or alcohol burner, from which the flame comes when you light it.
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What is a word equation?
A representation of a chemical reaction using the names of the chemicals only.
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What is yeast?
A group of single-cell fungi that contain enzymes to convert sugar into ethanol.
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What is the yield of a reaction?
The amount of something that is produced in a chemical reaction.
