Chemistry Paper 1 Flashcards
What is an atom?
The smallest part of an element that can exist
What is an element?
A substance made of only one type of atom
What is a compound?
A substance made of two or more different atoms chemically bonded together
How are compounds formed?
From chemical reactions
What is involved in a chemical reaction?
The formation of one or more new substances and an energy change
What is a molecule?
A substance made of more than one atom chemically bonded together
What is a mixture?
A substance made of more than one thing not chemically bonded together
How can mixtures be separated?
Physical processes (filtration, crystallisation, simple distillation, fractional distillation and chromatography)
Name three subatomic particles
Protons, neutrons, electrons
State the relative masses and charges of the subatomic particles
Mass: Protons: 1, neutrons: 1, electrons: 0.
Charge: Protons: +1, neutrons: 0, electrons: -1
What is the plum pudding model of the atom?
A ball of positively charge with negative electrons stubbed into it
What did the gold foil experiment (alpha particle scattering) prove?
The atoms have a dense nucleus with a positive charge
What did Chadwich discover?
The neutron
What did Bohr’s experiments show?
That electrons are in specific shells
What is the atomic number of an atom?
The number of protons in an atom
What is the mass number of an atom?
The number of protons + the number of neutrons in an atom
In the electron shell model, how are the subatomic particles arranged in an atom?
Protons and neutrons in the nucleus, electron orbiting in shells
Why is the number of electrons in an atom equal to the number of protons?
As their charges cancel out
How many electrons can go in the first shell?
2
How many electrons can go in the second and third shell?
8
What are the groups in the periodic table?
The columns, numbered 1, 2, 3, 4, 5, 6, 7, 0
What can the group tell you about the electrons in an atom?
How many electrons in the outer shell. E.g. carbon is in group 4 so has 4 electrons in the outer shell
What are the periods in the periodic table?
The rows in the periodic table
What can the period tell you about the electrons in an atom?
How many shells an atom has. E.g. carbon is in the second period so has two shells
Why do atoms have no overall charge?
The number of electrons and protons are equal
Approximately how large are atoms?
Radius is about 0.1nm
How large is the nucleus compared to the whole atom?
About 1/10,000 the size
What are isotopes?
Atoms of the same element with a different number of neutrons
What is abundance?
The % of atoms in a sample with a particular mass
What is the relative atomic mass of an element?
An average value for the mass that takes account of the abundance of the isotopes of the element
In the modern periodic table, how are the atoms arranged?
By their atomic number and in groups according to chemical properties
Why do elements in the same group have similar chemical properties?
Because they have the same number of electrons in their outer shell
Before the discovery of protons, neutrons and electrons, how did scientists organise elements?
By their atomic weight
Why did Mendeleev leave gaps in his periodic table?
For elements that had not yet been discovered
Which discovery meant that organising elements by their atomic weight was not always correct?
Isotopes
Where are metals on the periodic table found?
To the left and bottom of the periodic table
What is an ion?
An atom which has lost or gained electrons
What kinds of ions do metals and non-metals form?
Metals form positive, non-metals form negative
What name is given to the group 0 elements?
Noble gases
Why are the group 0 elements unreactive?
They have full outer shells so do not need to lose or gain electrons
How does the boiling point of group 0 elements change down the group?
Increases down the group
Explain why the group 1 elements are called alkali metals?
They are metals that form alkalis when they react with water
What are the products of the alkali metals in a reaction with oxygen, water, halogen?
Oxygen: metal oxide
Water: metal hydroxide + hydrogen
Halogen: metal halide
Explain why the group 1 elements get more reactive down the group
More electrons, more shielding, weaker electrostatic attraction from the nucleus to the outer shell, easier to lose an electron
What is the name given to elements in group 7?
Halogens
How does the boiling point of group 7 elements change down the group?
Increases down the group
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 an electron
What is a displacement reaction?
Where a more reactive element displaces a less reactive one from a compound
What are the three types of bond?
Covalent, ionic and metallic
What happens to the electrons in an ionic bond?
They are transferred
If an atom has gained electrons, what charge will it have as an ion?
Negative
If an atom has lost electrons, what charge will it have has an ion?
Positive
What type of elements will form ionic bonds?
Metal + non-metal
What is the charge on elements from group one and two?
Group 1: 1+, group 2: 2+
What is the charge on elements from group six and seven?
Group 6: 2-, group 7:1-
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
State the melting and boiling points of ionic compounds
High
Explain the melting and boiling points of ionic compounds
High due to strong electrostatic forces of attraction which require a lot of energy to break
Explain why ionic compounds do not conduct electricity when solid
The ions are not free to move and carry charge
Explain why ionic compounds conduct electricity when molten or in solution
The ions are free to move and carry charge
What happens to the electrons in a covalent bond?
They are shared
What type of elements will form covalent bonds?
Non-metal + non-metal
What two types of substance have covalent bonds?
Giant covalent substances and small molecules
How many bonds does each carbon have in diamond?
4
Explain why diamond and silicon dioxide have high melting points
Giant structures, strong covalent bonds between the atoms, requires a lot of energy to break
Explain why most covalent substances do not conduct electricity
There are no electrons or ions that are free to move and carry charge
Making full reference to structure and bonding in graphite, explain how it conducts electricity
Each carbon has 3 bonds, 1 electron is delocalised and therefore free to carry charge through the graphite
Explain why graphite can act as a lubricant
Weak forces between layers which are free to slide over each other
What type of substance are methane and water?
Small molecules
Describe the structure of small molecules
Strong covalent bonds between atoms, weak intermolecular forces holding the molecules together
Explain why small molecules have low melting points
It is a simple molecular substance with weak forces between the molecules (which are easy to break)
What is a polymer?
Millions of small molecules joined together in a chain to form a large molecule
Why do larger molecules have higher melting points than smaller ones?
Intermolecular force strengthens with increased molecule size
What is graphene?
One layer of graphite
What is graphene used for?
Electronics and composite materials
What is fullerene?
Substance made of carbon atoms arranged in a cage
What are nanotubes?
Cylindrical fullerenes
What are nanotubes used for?
Electronics, nanotechnology and materials
What is the conservation of mass?
That atoms cannot be created or destroyed
When a metal forms a metal oxide, why does the mass increase?
Because oxygen atoms have been added
When an acid reacts with a metal, why does the mass decrease?
Because a gas is produced and escapes
What is relative formula mass?
The sum of the relative masses of each atom in a compound
What are the four state symbols and what do they stand for?
(s) solid (l) liquid (g) gas (aq) aqueous
What symbol do we use for relative formula mass?
Mr
(HT) What is a mole?
A number of particles
(HT) What is Avogadro’s number?
6.022x1023
(HT) What formula relates moles, mass and Mr?
Mass = Mr x Moles
(HT) What is a limiting reactant?
A reactant that does not have enough mass to react with all the product
What is the unit for concentration?
g/dm3
Which formula relates concentration, mass and volume?
concentration = mass/volume
What is the reactivity series?
A list of elements ordered by their reactivity
How can metals be placed in order of their reactivity?
Add the metals to water or acid and see which ones react the most vigorously
What is the name for a reaction where oxygen is removed from a compound?
Reduction
Why is gold found in the Earth’s crust as the metal itself?
It is unreactive
What process is used to extract metals less reactive than carbon?
Reduction with carbon
What process is used to extract metals more reactive than carbon?
Electrolysis
What is an ore?
A material containing enough metal in it for it to be economically worthwhile to extract the metal.
What is a displacement reaction?
A reaction in which a more reactive element takes the place of a less reactive element in one of its compounds or in solution
Define oxidation in the context of loss and gain of electrons
Oxidation is the loss of electrons
Define reduction in the context of loss and gain of electrons
Reduction is the gain of electrons
Define acid in terms of pH
A substance with a pH of less than 7
Define acids in terms of ions
A substance which releases H+ ions in solution
State the three common acids and give their formulae
Hydrochloric acid, HCl(aq), Sulphuric acid, H2SO4 (aq), Nitric acid, HNO3;
Which ions do the common acids form in solution?
HCI forms H+ and CI-, H2SO4 forms 2H+ and SO42-, HNO3, forms H+ and NO3-
What is a neutral solution?
A solution with a pH of 7. Water is an example
How do you measure pH?
With an indicator or pH probe
What is a base?
A metal oxide, hydroxide or carbonate that will react with an acid. E.g. copper oxide
What is an alkali?
A soluble base. E.g. sodium hydroxide
Which ions are always present in a solution of an alkali?
OH-
What is a salt?
A compound formed when some or all of the hydrogen from an acid is replaced by a metal
What type of salts are formed by the three main acids?
Hydrochloric acid produces chlorides, sulphuric acid = sulphates, nitric acid = nitrates
What is a neutralisation reaction?
A reaction involving an acid that results in a neutral solution
Which ions always react together in a neutralization reactions between acids and alkalis?
H+ and OH-
Write the equation showing the reaction between H+ and OH- ions
Н+ + OH- -> H2O
Complete the equation:
metal + acid
-> salt + hydrogen gas
Complete the equation:
metal hydroxide + acid
-> salt + water
Complete the equation:
metal oxide + acid
-> salt + water
Complete the equation:
metal carbonate + acid
-> salt + water + carbon dioxide
How do you make a soluble salt from an acid?
React the acid with a base. E.g. to make copper sulphate react copper oxide with sulphuric acid
If a salt is in solution, how do you extract it as a solid?
Allow the water to evaporate and it will leave the salt behind as a solid (crystallisation)
What is a strong acid?
An acid which completely splits up into its ions in water. E.g. when HCl is in water all the HCI molecules split up into H* and CI-
What is a weak acid?
An acid which will have some molecules which do not split up into their ions.
E.g. in ethanoic acid only some of the molecules will have split up into the ethanoate ion and H* ions.
What is the relationship between the strength of an acid and its pH?
As an acid increases in strength the pH decreases.
What is a concentrated acid?
An acid where there are lots of acid particles in the water.
What is a dilute acid?
An acid where there are fewer acid particles in the water.
How does pH depend on the concentration of H+ in a solution?
As the concentration of H* increases by a factor of ten, the pH decreases by one
What is electrolysis?
Using electricity to produce elements from an ionic compound
What is an electrolyte?
A liquid or aqueous ionic compound
What is the name for the positive electrode?
The anode
What is the name for the negative electrode?
The cathode
Do positive ions move to the anode or the cathode?
Cathode
Do negative ions move to the anode or the cathode?
Anode
What are the two main disadvantages of using electrolysis to extract metals?
Requires a large amount of energy to melt the compounds and to produce the necessary electricity
Why is aluminium oxide mixed with cryolite when extracting aluminium?
To lower the melting point
What is produced at the anode and cathode in the electrolysis of aluminium oxide?
Aluminium at the cathode and oxygen at the anode
Why does the anode need to be replaced in the electrolysis of aluminium oxide?
The oxygen reacts with the carbon electrode to produce carbon dioxide.
For a simple ionic liquid, where is the metal produced?
Cathode
For a simple ionic liquid, where is the non-metal produced?
Anode
In the electrolysis of an ionic solution, when will hydrogen be produced?
If it is more reactive than hydrogen
In the electrolysis of an ionic solution, when will oxygen be produced?
If the non-metal is not a halogen
What can happen to water molecules in the electrolysis of solutions?
They break down into hydrogen and hydroxide ions
What is a half equation?
An equation which shows electron transfer at one of the electrodes
State the law of conservation of energy.
Energy cannot be created or destroyed, it can only transferred from one place to another.
What is an exothermic reaction?
A reaction where energy is transferred to the surroundings.
Give two examples of exothermic reactions.
Combustion, respiration
What happens to the temperature of the surroundings during an exothermic reaction?
Increases
What is an endothermic reaction?
A reaction where energy is transferred from the surroundings.
Give two examples of endothermic reactions.
Thermal decomposition reactions, citric acid and sodium hydrogencarbonate.
What happens to the temperature of the surroundings during an endothermic reaction?
Decreases
State two uses of exothermic reactions
Self-heating cans, hand warmers
State two uses of endothermic reactions
Some cooling sports injury packs
What is a reaction profile?
A diagram which shows whether the reactants have more or less energy than the products.
(HT) State which of bond breaking and bond making is endothermic and which is exothermic
Breaking: exothermic, making: endothermic
(HT) How do we work out the overall energy change of a reaction?
Work out the difference between the energy needed to break all the bonds the reactants and the energy release to form all the bonds in the products.
