AQA C2 CHEMISTRY

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  • Created by: bbyjujux
  • Created on: 19-04-17 00:11
what does an compound contain?
A compound contains two or more elements which are chemically combined
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what is covalent bonding
covalent bonding is sharing electrons - non-metals only
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what is ionic bonding
Ionic bonding is – transferring electrons - metal and non-metal
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what is chemical bonding
Chemical bonding: involves either transferring or sharing electrons in the highest occupied energy level (outer shell) of atoms to achieve the electronic structure of a noble gas (full outer shell)
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what do metals consist of?
Metals consist of giant structures of atoms arranged in a regular pattern.
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what are The electrons in the highest occupied energy levels ( outer shell)of metal atoms free to do?
they are delocalised and so they are free to move through the whole structure
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what does this create?
This creates a structure of positive ions with electrons between the ions holding them together by strong electrostatic attractions.
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polymers and nano materials-are there different types of polymers?
there are different types of polymers with different uses
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What do nano-materials have?
Nanomaterials have new properties because of their very small size.
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compounds are substances in which.......
atoms of two or more elements are chemically combined.
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what does chemical bonding involve?
Chemical bonding involves either transferring (IONIC BONDING) or sharing electrons (COVALENT BONDING)
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in the highest occupied energy levels (shells) of atoms in order to ...
achieve the electronic structure of a noble gas.
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atoms do what?
ATOMS GAIN, LOSE OR SHARE ELECTRONS TO HAVE A FULL OUTER SHELL LIKE THE NOBLE GASES.
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what do atoms form chemical bonds by transferring electrons
they form ions.
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what happens to atoms when they lose electrons
they become positively charged
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what are in group 1 of the periodic table?
the alkali metals
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alkali metals react with....
non-metal elements to form ionic compounds in which the metal ion has a single positive charge.
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what does alkali metals react with to form ionic compounds
non metal elments
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what are the elements in group 7 of the periodic table called
the halogens
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what do halogens react with to form ionic compounds
alkali metals
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the halogens react with the alkali metals to form....
ionic compounds in which the halide ions have a single negative charge.
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what is an ionic compound?
its a giant structure of ions
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what are ionic compounds held together by?
Ionic compounds are held together by strong ‘electrostatic forces of attraction’ between oppositely charged ions
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in what direction do these forces act?
These forces act in all directions in the lattice and this is called IONIC BONDING.
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what do Some covalently bonded substances consist of?
simple molecules such as H2, Cl2, O2, HCl, H2O, NH3 and CH4.
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what are other giant covalent structures
(macromolecules), such as diamond and silicon dioxide.
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what do simple molecules consist of
they consist of gases, liquids or solids that have relatively low melting points and boiling points
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do simple molecules conduct electricity
no they do not conduct electricity because the molecules do not have an overall electric charge
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what is intermolecular forces
Substances that consist of simple molecules have only weak forces between the molecules areintermolecular forces called
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why do ionic bonds have high boiling points
because of the large amounts of energy needed to break the many strong bonds.
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what can ionic bonds do when melted or dissolved in water
When melted or dissolved in water, ionic compounds conduct electricity because the ions are free to move and carry the current.
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atoms that share electrons can form what?
form giant structures or macromolecules.
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what are diamond and graphite an example of?
of giant covalent structures (lattices) of atoms.
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All the atoms in these structures......
are linked to other atoms by strong covalent bonds and so they have very high melting points..
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what is in graphite
In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.
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why does graphite have these properties
Graphite has these properties because of the weak intermolecular forces between the layers.
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why is diamond really hard
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.
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what is one electron in each carbon atom in graphite
its delocolised
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what does this allow the electrons to do
These delocalised electrons allow graphite to conduct heat and electricity.
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what is graphite similar to?
graphite is similar to metals in that it has delocalised electrons.
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what can carbon also form?
fullerness with different numbers of carbon atoms
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what can fullerness be used for?
drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials, e.g. in tennis rackets.
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what is the structure of fullerneses based on
hexagonal rings of carbon atoms
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what can metals conduct?
heat and electricity
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why can they conduct heat and electricity?
because of the delocalized electrons in their structures
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what are the layers of atoms in metalsable to do
they are able to slide over each other and so metals can be bent and shaped.
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what are alloys made of?
Alloys are usually made from two or more different metals.
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what is difficult for alloys to do and why?
it is difficult for alloys to slide of each other because the different sized atoms of the metals distort the layers in the structure
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so what makes alloys harder than
pure metals
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what can shape memory alloys do?
Shape memory alloys can return to their original shape after being deformed
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what does the properties of polymers depend on?
The properties of polymers depend on what they are made from and the conditions under which they are made.
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what do thermosoftening polymers consist of
Thermosoftening polymers consist of individual, tangled polymer chains.
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what do thermosetting polymers consist of
Thermosetting polymers consist of polymer chains with cross-links between them so that they do not melt when they are heated
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what does thermosofeting polymers have
Thermosoftening polymers in terms of have weak intermolecular forces of attraction between the polymer chains so are soft and can me melted easily
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nanosciene- what does nanoscience refer to?
Nanoscience refers to structures that are 1–100nm in size, of the order of a few hundred atoms. (VERY SMALL)
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what do nanoparticels show
Nanoparticles show different properties to the same materials in bulk and have a high surface area to volume ratio
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what does this may lead to the development of
new computers, new catalysts, new coatings, highly selective sensors, stronger and lighter construction materials, and new cosmetics such as sun tan creams and deodorants.
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what is The relative formula mass (Mr) of a compound
its the sum of the relative atomic masses of the atoms in the numbers shown in the formula.  
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what is The relative formula mass of a substance, in grams, known as
its is known as one mole of that substance
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analyzing substances- how can elements and compounds be detected?
Elements and compounds can be detected and identified using Instrumental methods.
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what are instrumental methods
Instrumental methods are accurate, sensitive and rapid and are particularly useful when the amount of a sample is very small.
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what can Chemical analysis can be used for
it can be used to identify additives in foods.
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what can artificial colors be detected and identified by
paper chromatography
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what is Gas chromatography linked to mass spectroscopy (GC-MS an example of
an instrumental method
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what does Gas chromatography allow?
its allows the separation of a mixture of compounds
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The time taken for a substance to travel through the column can be used to...
help identify the substance
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what can The output from the gas chromatography column link to?
it can be linked to a mass spectrometer, which can be used to identify the substances leaving the end of the column
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what can The mass spectrometer can also give?
the relative molecular mass of each of the substances separated in the column.
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how does gc-ms work
different substances, carried by a gas, travel through a column packed with a solid material at different speeds, so that they become separated
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what does ■ the number of peaks on the output of a gas chromatograph show?
it shows the number of compounds present
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what is the moclecular mas given by?
The molecular mass is given by the molecular ion peak.
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what does the position of the peaks on the output indicate?
the position of the peaks on the output indicates the retention time
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what can a mass spectrometer dentify
a mass spectrometer can identify substances very quickly and accurately and can detect very small quantities.
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how can the percentage of an element in a compound be calculated?
it can be calculated from the relative mass of the element in the formula and the relative formula mass of the compound.
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how can the empirical formula of a compound can be calculated
it can be calculated from the masses or percentages of the elements in a compound.
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how can the The masses of reactants and products be calculated
from balanced symbol equations.
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what is the yield knows as
The amount of a product obtained
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what is a percentage yield
When compared with the maximum theoretical amount as a percentage, it is called the percentage yield.
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why is the % yield never 100%
Even though no atoms are gained or lost in a chemical reaction, it is not always possible to obtain the calculated amount of a product
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why
the reaction may not go to completion because it is reversible ■ some of the product may be lost when it is separated from the reaction mixture ■ some of the reactants may react in ways different from the expected reaction.
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what can some chemical reactions, the products of the reaction can react to produce
the original reactants. such reaction are called reversible reactions and are represented as A+B C+D
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rates of reaction- what can the rate of a chemical reaction be found by?
can be found by measuring the amount of a reactant used or the amount of product formed over time:
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what are the 2 definitions of the rate of reaction
Rate of reaction = amount of reactant used time Rate of reaction = amount of product formed time
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when can Chemical reactions only occur
it can only occur when reacting particles collide with each other and with sufficient energy.
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what is an activation energy
The minimum amount of energy particles must have to react is called the activation energy.
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what can does the temperature do to the rate of reaction to particles
it increases the speed of the reacting particles so that they collide more frequently and more energetically. This increases the rate of reaction.
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what does increasing the pressure do to the rate of the reaction of gases?
Increasing the pressure of reacting gases increases the frequency of collisions and so increases the rate of reaction.
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what does increasing the rate of concretion do to reactants in solutions?
it increases the frequency of collisions and so increases the rate of reaction
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what does Increasing the surface area do to solid reactants
it increases the frequency of collisions and so increases the rate of reaction
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what are catalysts not used up for?
catalyts are not used up during the reaction.Different reactions need different catalysts.
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what are catalyts important for?
Catalysts are important in increasing the rates of chemical reactions used in industrial processes to reduce costs.
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what happens when chemical reactions occur
energy is transferred to or from the surroundings.
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what does exothermic do
An exothermic reaction is one that transfers energy to the surroundings. (temp increases)
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what are examples of exothermic reactions include combustion,
, many oxidation reactions and neutralisation.
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exothermic reaction is an...
Everyday uses of exothermic reactions include self-heating cans (eg for coffee) and hand warmers
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what is an edothermic reaction?
An endothermic reaction is one that takes in energy from the surroundings. (temp decreases
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what does Endothermic reactions include?
thermal decompositions
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what are some sport injury packs based upon?
endothermic reactions.
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what happens if a reversible reaction is exothermic is in one direction,
it is endothermic in the opposite direction. The same amount of energy is transferred in each case.
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Making salts- what are the state symbols in equation
The state symbols in equations are (s = solid), (l= liquid), (g) and (aq = aqueous).
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Soluble salts can be made by reacting acids with...
metals – not all metals are suitable; some are too reactive and others are not reactive enough insoluble bases – the base is added to the acid until no more will react and the excess solid is filtered off alkalis – an indicator can be used to show
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how can insoluble salts be made?
These can be made by mixing appropriate solutions of ions so that a precipitate is formed.
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what can precipitation be used for
Precipitation can be used to remove unwanted ions from solutions, for example in treating water for drinking or in treating effluent
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what does the the particular salt producein any reaction between an acid and a base or alkali depend on
the acid used (2nd word of the name) (hydrochloric acid produces chlorides, nitric acid produces nitrates, sulphuric acid produces sulfates) ■ the metal in the base or alkali (1st word in the name)
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what are Metal oxides and hydroxides
bases.
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what are soluble hydroxides called
alkalis
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what does ammonia dissolve in
Ammonia dissolves in water
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to produce what
to produce an alkaline solution. It is used to produce ammonium salts.
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what are Ammonium salts
important as fertilisers
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what does Hydrogen ions, H+(aq), make
solutions acidic
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what does hydroxide ions, OH–(aq), make
solutions alkaline
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what is a ph scale
The pH scale is a measure of the acidity or alkalinity of a solution
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what does hydrogen react with in neutralisation reactions
hydrogen ions react with hydroxide ions to produce water. This reaction can be represented by the equation: H+(aq) + OH–(aq) ➞ H2O(l)
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electrolysis- what happens When an ionic substance is melted or dissolve in water
the ions are free to move about within the liquid or solution.
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what happens if you pass an electric current through ionic substances that are molten for example lead bromide or in solution
breaks them down into elements. This process is called electrolysis and the substance that is broken down is called the electrolyte.
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what happens during electrolysis
During electrolysis, positively charged ions move to the negative electrode, and negatively charged ions move to the positive electrode.
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what is electrolysis used to do
Electrolysis is used to electroplate objects. This may be for a variety of reasons and includes copper plating and silver plating
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what can reactions at electrodes be represented by?
Reactions at electrodes can be represented by half equations, for example: 2Cl– ➞ Cl2 + 2e– (OXIDATION
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what is aluminium manufactured by?
.Aluminium is manufactured by the electrolysis of a molten mixture of aluminium oxide and cryolite.
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when does Aluminium form at
Aluminium forms at the negative electrode Al3+ + 3e- Al (reduction) And oxygen at the positive electrode. 2O2- O2 + 4e- (oxidation)
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what happens to the negative electrode?
positively charged ions gain electrons (reduction)
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what happens to the positive electrode?
negatively charged ions lose electrons (oxidation).
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what is OILRIG
OXIDATION IS LOSS, REDUCTION IS GAIN
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production of aluminum using electrolysis- what is the positive electrode made of?
The positive electrode is made of carbon, which reacts with the oxygen to produce carbon dioxide.
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why is crylite used in this process
because it lowers the temp at which aluminium oxide melts
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electroylysis of sodium chloride- what does The electrolysis of sodium chloride solution produce
hydrogen and chlorine Sodium hydroxide solution is also produced.
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these are important....
reagents for the chemical industry, eg sodium hydroxide for the production of soap and chlorine for the production of bleach and plastics.
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what happens at the anode
AT THE ANODE Cl- and OH- are attracted Cl- loses 1 electron to form chlorine gas 2Cl- Cl2 + 2e- OXIDATION (OILRIG)
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what happens at the cathode
AT THE CATHODE Na + and H + attracted Hydrogen gains 1 electron to form hydrogen gas 2H+ + 2e- H2 REDUCTION (OILRIG)
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additional information
The Na+ and OH – , bond together in the electrolyte to make sodium hydroxide NaOH
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additional information
Also OH– and H+ ions in the electrolyte which have broken up from water
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what is ionic bonding

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Card 5

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