AQA GCSE Combined Science Chemistry - Paper 1
Terms in this set (283)
C1 Atomic Structure
Atoms are the particles that make up everything
What are atoms?
An element is a substance in which all the atoms are the same
What is an element?
Elements are shown in the Periodic table
Where are elements shown?
There are around 118 elements
How many elements are there?
A compound is a substance that contain two or more elements chemically combined
What is a compound?
The properties of compounds are usually different to the elements that they are made from
Describe the properties of compounds
A mixture is a substance with different elements or compounds not chemically combined
What is a mixture?
An example of a mixture is sand and water as they are not chemically combined and can be separated by physical means
Give an example of a mixture
A molecule is a substance that has any elements chemically joined
What is a molecule?
A chemical formula tells the elements in a molecule and the number of atoms of each element
What does a chemical formula tell you about a molecule?
Each element symbol starts with a capital letter, if there is a second letter it is in lower case
How is a chemical formula presented?
Give an example of a chemical formula
State symbols show the physical state of the substance solid (s), liquid (l), gas (g), or dissolved in water (aq)
What are state symbols?
-Good conductors of heat and electricity
-High melting and boiling points
Name three properties of Metals
-Bad conductors of heat and electricity
-Low melting and boiling points
Name three properties of Non-Metals
Four different ways of separating mixtures are filtration, crystallisation, distillation or chromatography
State the four different ways of separating mixtures
Pour your mixture onto the filter paper, the liquid simply passes through the filter paper into the flask. The insoluble solid cannot pass through and so it stays on the paper
Describe the process of filtration
Use the method of filtration to filter off any excess soluble solid. Evaporate the mixture then transfer the hot mixture onto a dish. Crystals are formed when the mixture has cooled
Describe the process of crystallisation
First we evaporate the mixture by heating it, the dissolved solid then vaporises. These vapours condense in the condenser, the dissolved solid then flows into the beaker and liquid stays in the flask
Describe the process of simple distillation
Take a strip of filter paper and draw a line on the bottom of the paper. Put a small drop of ink on the line, take a jar full of water up to the line and put the filter paper in. As the water moves up we see different colours on the paper these are the dyes in the ink
Describe the process of chromatography
Early ideas of the structure of atoms stated that they are tiny spheres that cannot be divided
What were the early ideas of the structure of atoms?
The plum pudding model is what scientists suggested is the structure of atoms is after the discovery of the electron
What is the plum pudding model?
The plum pudding model suggested that an atom is a ball of positive charge with negative electrons in embedded in it
Describe the plum pudding model
Rutherford took a piece of gold foil, he then fired tiny positive alpha particles at the gold foil
Describe how Rutherford carried out the gold foil experiment
Rutherford observed that most of the particles when straight through the gold foil and sometimes the alpha particles bounce back of the gold foil
What did Rutherford observe in the experiment?
Rutherford discovered that atoms are mainly empty space as most of the alpha particles went straight through the gold atoms and that the nucleus of the atom is very small as only a small number of alpha particles bounce back
What did Rutherford discover from these observations?
The nuclear model states that most of an atom is empty space, in the centre is the nucleus which contains protons and neutrons around the edge we find electrons
Describe the structure of the nuclear model
What is the Relative mass and the relative charge of protons, neutrons and electrons?
Because atoms have have no overall charge
Why do atoms have the same number of protons as electrons?
An ion is a charged particle, it is possible to get positive or negative ions
What is an Ion?
Atoms of the same element with different numbers of neutrons are called isotopes
What is an Isotope?
The mass number is the number on the top of an element it is the number of proton and neutrons combined
What is the mass number of an element?
The atomic number is the number on the bottom it is number of protons in an atom, which is the same as the number of electrons
What is the atomic number of an element?
Shell 1 : 2 electrons
Shell 2 : 8 electrons
Shell 3 : 8 electrons
How many electrons can you fit in the first, second and third shells?
A set of number to show the arrangement of electrons in their shells, eg. [2,6]
What is an Electronic structure?
C2 The periodic table
He arranged the elements in order of increasing atomic mass, he saw that every eighth element reacted in a similar way
What did John Newlands periodic table look like?
He arranged the elements in order of increasing atomic mass, he switched the order of some elements to the fitted in the patterns of other elements. He left gaps for undiscovered elements
What did Dmitri Mendeleev's periodic table look like?
Elements are arranged in order of atomic number, the elements are organised in groups and periods which have the similar properties
What does the modern periodic table look like?
Elements with similar chemical properties are grouped together in groups
Why are elements in the periodic table grouped the way they are?
Elements in a group have similar chemical properties because they all have the same number of electrons in their outer energy level therefore react similarly
Why do elements in a group have similar chemical properties?
Group 1: alkali metals
Group 2: alkaline earth metals
Group 7: halogens
Group 0: noble gases
What are the names of group 1, 2, 7 and 0?
Where are the metals and non-metals located on the periodic table?
When metals react they lose electrons to achieve a full outer energy level
What happens to metals when they react?
Group 1 form 1+ ions
Group 2 form 2+ ions
What ions do metals from group 1 and 2 form?
Lithium, Sodium, Potassium,
Rubidium, Cesium, Francium
Name the elements in Group 1
In the reaction one group 1 metal transfers its outer electron to the oxygen another group 1 metal does the same, now all the atoms have a full outer energy level. The metals have a 1+ charge and the oxygen has a 2- charge
Describe the reaction of a group 1 metal and oxygen in terms of electrons
In the reaction a group 1 metal transfers its outer electron to the chlorine, now both atoms have a full outer energy level. The metals have a 1+ charge and the chlorine has a 1- charge
Describe the reaction of a group 1 metal and chlorine in terms of electrons
Metal + Water →
Metal Hydroxide + Hydrogen
What is the word equation for the reaction of group 1 metals and water?
When water reacts with lithium the reaction is fast and there is fizzing. When it reacts with sodium the reaction is very fast and gas is produced. When it reacts with potassium the reaction is extremely fast and there is a small flame. In all the reactions the water turns alkaline
Describe the reaction of the first three group 1 metals and water
Group 1 metals react faster as you move down the column
Describe the correlation of the reactivity of a group 1 metal and it's location in the table
As we move down the group the outer electron is less attracted to the nucleus and easier to lose because it has a greater distance between the positive nucleus
Why are group 1 metals more reactive as we move down the group?
Group 1 metals have low melting points and a low density, they are soft metals and react very rapidly
Name some properties group 1 metals
Fluorine, Chlorine, Bromine, Iodine, Astatine
What elements are in group 7?
Group 7 elements need 1 electron to fill their outer shell so they just share an electron with another group 7 element, this is known as covalent bonding
How do group 7 elements achieve full outer shells?
Group 7 elements have a higher melting and boiling point as you move down the column
Describe the correlation of the melting and boiling point of a group 7 element and it's location in the table
Group 7 elements form covalent compounds when they react with other non-metal atoms so the electrons are shared
What is formed when group 7 elements react with non-metal atoms?
Group 7 elements form ionic compounds when they react with metals so the electrons are transferred
What is formed when group 7 elements react with metals?
When a group 7 element reacts with a metal the group 7 element gains and electron and forms a 1- ion
When a group 7 element reacts with a metal what charges does the group 7 element have?
Group 7 elements have a lower reactivity as you move down the column
Describe the correlation of the reactivity of a group 7 element and it's location in the table
An element at the top has less distance between the nucleus and the outer energy level so it gains electrons easier, an element at the bottom has a greater distance between the nucleus and the outer energy level so it is harder to gain electrons
Why is it harder for an element at the bottom of the group to gain an electron that an element at the top of the group?
A more reactive halogen can displace a less reactive halogen from an aqueous solution of its salt
Explain what happens in a displacement reaction
Sodium Bromide + Fluorine → Sodium + Bromine Fluoride
Give an example of a displacement reaction
Helium, Neon, Argon, Krypton, Xenon, Radon
What elements are in group 0?
Group 0 elements have full outer shells and so they don't need to react to fill up their shells
Why are group 0 elements unreactive?
Group 0 elements have a lower melting and boiling point as you move down the column
Describe the correlation of the melting and boiling point of a group 0 element and it's location in the table
Transition metals are located in the centre of the periodic table
Where are transition metals located?
Transition metals are hard and strong and have a high density and melting point, they are good conductors of heat and electricity. They for coloured compounds and can be used as catalysts
Name some properties of transition elements
C3 Structure and bonding
The three states of matter are solids, liquids and gases
What are the three states of matter?
The particle theory describes the movement and arrangement of particles
What is the particle theory?
The particles in a solid are packed closely together in a fixed arrangement, they vibrate constantly
Describe the particles in a solid
The particles in a liquid are close together in a changing, random arrangement, they can move around
Describe the particles in a liquid
The particles in a gas are much further apart in a random arrangement, they move very quickly
Describe the particles in a gas
A solid turns into a liquid when it reaches it's melting point. As the temperature increases the particles vibrate faster until the forces between them breaks and a liquid is formed
When does a solid become a liquid?
A liquid turns into a gas when it reaches it's boiling point. As the temperature increases the particles move around faster, at the boiling point bubbles of gas form and rise to the surface and a gas is formed
When does a liquid become a gas?
Substances with higher and melting and boiling points have stronger forces between the particles
How are the forces between particles affected by melting and boiling points?
Elements form compounds by gaining or losing electrons or by sharing electrons
How do elements form compounds?
In ionic bonding a metal reacts with a non-metal
In ionic bonding what two types of element react?
Electrons from the metal is transferred to the non-metals to give both elements full outer shells
How are full outer energy levels achieved in ionic bonding?
Ionic compounds transfer electrons to achieve full outer shells
How do ionic compounds achieve full outer shells?
Group 1/ 1+
Group 2/ 2+
Group 3/ 3+
Group 5/ 3-
Group 6/ 2-
Group 7/ 1-
What ions do Group 1, 2, 3, 5, 6 and 7 elements form?
Ionic compounds form a giant ionic lattice where every positive ion is surrounded by a negative ions
Describe the structure of an ionic compound
Ionic compounds are held together by strong electrostatic forces
What are ionic compounds held together by?
The properties of ionic compounds are that they can transfer electrons when they react, they have high melting and boiling points and can conduct electricity when they are not solids
What are the properties of ionic compounds
Tonic compounds have high melting and boiling points because the strong electrostatic forces require a lot of heat energy to break
Why do ionic compounds have high melting and boiling points?
Ionic compounds can't conduct electricity when they are solids because the ions cannot move, they are locked in place by strong electrostatic forces
Why can't ionic compounds conduct electricity when they are solids?
Ionic compounds can conduct electricity when they are liquids or dissolved in water because the ions can now move and carry the charge
Why can ionic compounds conduct electricity when they are liquids or dissolved in water?
In covalent bonding happens between two non-metals
In covalent bonding what two types of element react?
In covalent bonding full outer energy levels are achieved by two non-metals sharing electrons
How are full outer energy levels achieved in covalent bonding?
The properties covalent molecules are that they share electrons when they react, they have a low melting and boiling points and cannot conduct electricity
What are the properties of covalent molecules
Covalent Molecules have a low melting and boiling point because the bond between the molecules is weak and so it doesn't need a lot of energy to break the intermolecular forces
Why do Covalent Molecules have a low melting and boiling point?
Covalent Molecules can't conduct electricity because they don't have an overall electric charge
Why can't Covalent Molecules conduct electricity ?
Giant covalent molecules are solids at room tempreature
What state are giant covalent molecules at room temperature?
Giant covalent molecules have high melting and boiling points because they have millions of strong covalent bonds
Do giant covalent molecules have high or low melting and boiling points?
Three giant covalent molecules are diamond, silicon dioxide and graphite
Name three giant covalent molecules
Diamond is formed from the element carbon
What element is diamond formed from?
Carbon forms 4 bonds
How many bonds does Carbon form?
Diamond has a giant molecular structure. Each carbon atom is covalently bonded to four other carbon atoms, diamonds contains many strong covalent bonds
Describe the structure of a diamond
Diamond cannot conduct electricity
Can diamond conduct electricity?
Diamond cannot conduct electricity because there are no free electrons to carry the electrical charge
Why can't diamond conduct electricity?
Diamond has a high melting and boiling point
Does diamond have a high or low melting and boiling point?
Diamond has a high melting and boiling point because it is made up of strong covalent bonds
Why does diamond have a high melting and boiling point?
Silicon dioxide has a giant covalent structure it is made up of silicon and oxygen atoms, each silicon atom is covalently bonded to four oxygen atoms, each oxygen atom is covalently bonded to two silicon atoms
Describe the structure of silicon dioxide?
The melting point of diamond is 3700⁰C
What is the melting point of Diamond?
Silicon dioxide has a high melting and boiling point
Does silicon dioxide have a high or low melting and boiling point?
Silicon dioxide has a high melting and boiling point because it is made up of strong covalent bonds and a lot of heat energy is required to break its bonds
Why does silicon dioxide have a high melting and boiling point?
Graphite is formed from carbon
What element is Graphite made of?
In Graphite each carbon atom forms three covalent bonds
In Graphite how many bonds does carbon form?
Graphite has a giant covalent molecular structure it contains many layers of carbon atoms each carbon atom covalently bonded to three other carbon atoms, the layers are held by weak forces between them
Describe the structure of Graphite
Graphite has a high melting and boiling point
Does graphite have a high or low melting and boiling point?
Graphite has a high melting and boiling point because it is made up of strong covalent bonds and a lot of heat energy is required to break its bonds
Why does graphite have a high melting and boiling point?
Graphite is a good conductor heat and electricity
Is graphite a good or bad conductor of heat and electricity?
Graphite is a good conductor heat and electricity because when the carbon atoms bond together each carbon atom has an electron that is not in a covalent bond, these delocalised electrons can move and they can conduct heat and electricity
Why is graphite a good conductor of heat and electricity?
Delocalised electrons are electrons that can move meaning they can conduct heat and electricity
What are delocalised electrons?
Graphite is soft and slippery
Describe the texture of graphite
Graphite is soft and slippery because graphite is made up of hexagonal rings in on top of each other and there are no covalent bonds between the layers so the layers can slide making graphite soft and slippery
Why is graphite soft and slippery?
Graphene is a single layer of graphite and it is one atom thick
Describe the structure of graphene
Graphene is a good conductor of electricity
Is graphene a good or bad conductor of electricity?
Graphene is a good conductor of electricity because it has delocalised electrons
Why is graphene a good conductor of electricity?
Graphene is very strong
Is graphene strong or weak?
Fullerenes are molecules of carbon atoms with hollow shapes they have hexagonal rings of carbon atoms, however they can also have rings with five or seven carbon atoms
Describe the structure of fullerenes
An example of a fullerene is Buckminsterfullerene
Name an example of a fullerene
Fullerenes can be used for pharmaceutical delivery, lubricants and as catalysts
What can fullerenes be used for?
Carbon nanotubes are a group of fullerenes that are shaped into long cylinders, they are made of rings formed from six carbon atoms
What are carbon nanotubes?
Carbon nano tubes have high tensile strength, they are good conductors of heat and electricity
What are the properties of carbon nanotubes?
Carbon nanotubes are used to reinforce materials such as tennis rackets
What can carbon nanotubes be used for?
Metals consist of a giant structure of atoms arranged in regular layers, the electrons in the outer energy level of each atom are delocalised
Describe the structure of a metal
There are strong electrostatic forces of attraction between the negative delocalised electrons and the positive ions
What are the forces of attraction between the negative delocalised electrons and the positive ions?
The electrostatic attractions in metals are called metallic bonds
What are the electrostatic attractions in metals called?
Metals have a high melting and boiling point
Do metals have a low or high melting and boiling point?
Metals have a high melting and boiling point because a lot of heat energy is needed to break the strong metallic bonds
Why do metals have a high melting and boiling point?
Metals are good conductors of heat and electricity
Are metals good or bad conductors of heat and electricity?
Metals are good conductors of heat and electricity because the delocalised electrons can move and can carry the electric charge and thermal energy
Why are metals good conductors of heat and electricity
Metals are malleable meaning they can be bent and shaped
Are metals malleable?
Metals can be bent and shaped because the layers of atoms are able to slide over each other
Why can metals be bent and shaped?
An alloy is a mixture of metals
What is an alloy?
Alloys are not malleable
Are alloys malleable?
Alloys aren't malleable because the different sizes of atoms distorts the layer making it hard for them to slide over each other
Why are alloys not malleable?
A nanometre is 1 x 10⁻⁹ metre
What is the size of a nanometre?
A coarse particle is between 1 x 10⁻⁵ and 1 x 10⁻⁶ meters
What is the size of a coarse particle?
A fine particle is between 1 x 10⁻⁷ and 2.5 x 10⁻⁶ meters
What is the size of a fine particle?
Nanoparticles are used in medicines, creams and catalysts
Name some uses of nanoparticles
It is possible that nanoparticles can be absorbed into they body and enter our cells, this could be harmful
What is a risk of nanoparticles?
C4 Chemical calculations
The law of conservation of mass states that the total mass of the reactants in a chemical reaction is equal to the mass of the product
What is the Law of Conservation of Mass?
The gas in the reaction will float away so it appears to break the law
Explain why reactions involving gas appear to break the law?
Relative Atomic Mass is the final mass that takes in consideration all the isotopes of an element
What is the Relative Atomic Mass (Ar)?
(% x Atomic mass)+
(% x Atomic mass) / 100
How do you calculate the Ar?
Relative Molecular Mass is the mass of a molecule that takes in consideration all the isotopes of all the elements in the molecule
What is the Relative Molecular Mass (Mr)?
Calculate the Ar of each element and then add them all up
How do you calculate the Mr?
Moles are used to measure chemical amounts
What are Moles?
One mole of a substance is
the Ar/Mr in grams
What does 1 mole of a substance equal?
Avogadro's numbers is
6.02 x 10²³
What is Avogadro's number?
What is the Magic triangle for calculating Mass, Moles and the Ar/Mr?
To balance an equation using moles we need to calculate the number of moles of all the chemicals then put the number of moles in front of the chemical the divide all the numbers with smallest number, the equation is now balanced
How do we balance equations using moles?
The reactant that get used up first in a reaction is called the limiting reactant
What is the Limiting Reactant?
The Limiting Reactant Determines the amount of product formed in a reaction
What does the Limiting Reactant Determine?
The Yield of a Chemical Reaction is how much you actually made
What is the Yield of a Chemical Reaction?
The Percentage Yield compares the amount made with the maximum amount that could be made
What does the Percentage Yield compare?
Percentage Yield =
(Mass/Max Mass) x 100
How do you calculate the Percentage Yield?
It is not possible to achieve 100% yield in a chemical reaction as some of the product may be lost and the reactants may react in differently way so we don't get the product expected, reversible reactions may not go to completion
Why is it not possible to achieve 100% yield in a chemical reaction
Atom economy is a measure of the amount of starting materials that end up as useful products
What is atom economy?
Reducing the production of unwanted products saves money and increases sustainable by not wasting resources
Why is reducing the amount of unwanted products useful?
Atom Economy =
(M/Ar of Desired product/
M/Ar of reactants) x 100
How do you calculate atom economy?
The atom economy can't be over 100% because that would mean we're creating atoms which is impossible
Why can't the atom economy be over 100%?
The concentration of a solution tells us the number of moles of a solute in a given volume of the solution
What does the concentration of a solution tell you?
The unit used to measure concentration mol / dm³
What is the unit used to measure concentration?
What is the concentration magic triangle?
1000 cm = 1 dm
How many centimeters is one decimetre?
One mole of gas occupies a volume of 24dm³
How many decimetres of volume does one mole of gas occupy?
Room temperature is 20⁰C
What is tempreature is room temperature?
Volume= Number of moles x 24
How do calculate volume?
Titrations are used to find the exact volumes of acid and alkali that react with each other
What are titrations used for?
Fill up a flask with 25cm³ of sodium hydroxide solution, then add 5 drops of indicator to the solution, then place the flask on a white tile so we can see the colour change. Fill a burette with sulfuric acid. Slowly add the acid into the alkali until it nuetralsises, read the volume, record the results on the burette
How do you carry out a titration?
C5 Chemical changes
When a metal reacts with oxygen a metal oxide is formed
What is formed when a metal reacts with oxygen?
Metal + Oxygen → Metal oxide
What is the word equation for the reaction of metals and oxygen?
In an oxidation reaction oxygen is gained
What happens in an oxidation reaction?
In an reduction reaction oxygen is lost
What happens in an reduction reaction?
Metal + Water → Metal Hydroxide + Hydrogen
What is the word equation for the reaction of a group 1 metal and water?
Calcium+ Water → Calcium Hydroxide + Hydrogen
What is the word equation for the reaction of a calcium and water?
The reactivity series places metals in increasing order of reactivity
What is the Reactivity Series?
What is a mnemonic to remember the reactivity series?
Metals lose electrons when they react and so they form positive ions
What type of ion does a metal form when it reacts?
The reactivity of a metal depends on its ability to lose electrons and form a positive ion
What does the reactivity of a metal depend on?
Unreactive metals such as gold are found in the Earth
Where are unreactive metals such as gold found?
Reactive metals such as iron are found in compounds, in the case of iron it is found in a mineral of iron oxide
Where are reactive metals such as iron found?
Reduction is gain of electrons
What is reduction?
Oxidation is loss of electrons
What is oxidation?
Displacement Reactions are reactions in which a more reactive element replaces a less reactive element in one of its compounds or in a solution
What is a displacement reaction?
The element being displaced need to be less reactive than the element that is displacing it
What is needed for a displacement reaction?
Magnesium + Iron Oxide → Magnesium Oxide + Iron
Show an example of a displacement reaction
The iron atoms have been reduced because they lost electrons
Have the iron atoms been oxidised or reduced?
The magnesium atoms have been oxidised because they gained oxygen
Have the magnesium atoms been oxidised or reduced?
The carbon displaces the less reactive element
How is carbon used to extract elements?
Carbon + Iron Oxide → Carbon Dioxide + Iron
Give an example of how carbon would be used to extract iron from iron oxide
An example of an acid is hydrochloric acid, HCl
Give an example of an acid
Acids produce hydrogen ions in aqueous solution
What do acids produce in aqueous solution?
HCl → H⁺ + Cl⁻
Give an example of an acid producing hydrogen ions
Bases are chemicals which can neutralise acids and produce a salt and water
What are bases?
A example of a base is copper oxide
Give an example of a base
Bases that are soluble in water are called alkalis
What are bases that are soluble in water called?
Aqueous solutions of alkalis contain hydroxide ions
What do aqueous solutions of alkalis contain?
NaOH → Na⁺ + OH⁻
Give an example of an aqueous solution of alkalis that contains hydroxide ions
The pH scale is a scale from 1-14 that tell us the acidity or alkalinity of a solution
What is the pH scale?
Colours towards red show an acidic solution
What do colours towards red show?
Colours towards purple show an alkali solution
What do colours towards purple show?
A neutralisation reaction occurs, the hydrogen ions react with hydroxide ions to form water
What happens when you react an acid with an alkali?
All acids contain hydrogen
What element do all acids contain?
Acid + Metal → Salt + Hydrogen
What is the word equation for the reaction between an acid and a metal?
Hydrochloric acid produces salts that end in -chloride
What are the endings of salts produced from hydrochloric acid?
Sulfuric acid produces salts that end in -sulfate
What are the endings of salts produced from sulfuric acid?
Nitric acid produces salts that end in -nitrate
What are the endings of salts produced from nitric acid?
Hydrochloric Acid + Magnesium → Magnesium Chloride + Hydrogen
What is formed when hydrochloric acid reacts with magnesium?
Sulfuric Acid + Iron → Iron Sulphate + Hydrogen
What is formed when sulfuric acid reacts with iron?
The metal displaces the hydrogen from the acids to form a salt and the hydrogen is released as a gas
What happens to the elements in the reaction between an acid and metal?
Acid + Base → Salt + Water
What is formed when an acid reacts with a base?
Acid + Alkali → Salt + Water
What is formed when an acid reacts with an alkali?
Salts contain a positive ion which comes from the base or alkali and a negative ion which comes from the acid
What type of ions do salts contain?
Acid + Metal Carbonate → Salt + Water + Crabon dioxide
What is formed when an acid reacts with a metal carbonate?
Add copper oxide to sulphuric acid and stir, warm gently. The solution turns blue showing that copper sulphate is being formed, excess black copper oxide can be seen. Filter the solution to remove excess copper oxide and evaporate the water so that crystals of copper sulphate start to form. Stop heating when you see the first crystals appear at the edge of the solution , leave the rest of the water to evaporate, this gives you large crystals. Any small excess of solution on the crystals can be removed by dabbing between filter papers, then leaving to dry
How do you make copper salt?
Strong acids are acids that fully ionise in aqueous solutions
What are strong acids?
We can tell if an acid is a strong acid by looking at it's equation, strong acid equations go only one way
How can we tell if an acid is a strong acid?
Weak acids are acids that partially ionise in aqueous solutions
What are weak acids?
We can tell if an acid is a weak acid by looking at it's equation, weak acid equations are reversible
How can we tell if an acid is a weak acid?
Electrolysis is the processes that uses electricity to break down ionic compounds into elements
What is electrolysis?
Solid ionic compounds cannot conduct electricity because the ions are locked in place by strong electrostatic forces and cannot move
Why can't solid ionic compounds conduct electricity?
Melted ionic compounds can conduct electricity because the electrostatic forces are broken and the ions can move
Why can melted ionic compounds conduct electricity?
Electrolytes are liquids or solutions that can conduct electricity they are the solution being broken down
What are electrolytes?
In electrolysis there are two electrodes, the negative cathode and the positive anode and there is an electrolyte solution
What is the equipment used to preform electrolysis?
Electrodes are made of inert substance that doesn't react with the products such as graphite
What are electrodes usually made of?
The aluminium oxide is mixed with cryolite to lower the melting point, the solution is used as the electrolyte, the positive aluminium ions are attracted to the cathode and the negative oxide ions are attracted to the positive anode, the aluminium is reduced and the oxide is oxidised
Describe the stages of the electrolysis of aluminium oxide
Copper sulfate solution is used as the electrolyte, the positive copper ions are attracted to the cathode and the negative sulfate ions are attracted to the positive anode, the copper is reduced and the sulfate is oxidised
Describe the stages of the electrolysis of copper sulfate
The anode must be replaced regularly because the oxygen produced at the anode reacts with the carbon in the graphite forming carbon dioxide gas
Why must the anode be replaced regularly?
C7 Energy changes
Exothermic reactions are reactions that transfer energy to their surroundings
What are exothermic reactions?
In an exothermic reaction the temperature of the surroundings gets increases
What happens to the temperature of the surroundings in an exothermic reaction?
Three examples of exothermic reactions are combustion, oxidation and neutralisation
Give three examples of exothermic reactions
Two uses of exothermic reactions are hand warmers and self-heating cans
What are two uses of exothermic reactions?
What is the energy profile diagram for a exothermic reaction
In an exothermic reaction the reactants have more energy that the products
In an exothermic reaction what has more energy the reactants or the products?
In an exothermic reaction the reactants have more energy that the products because energy is being transferred from the reaction to the surroundings
Why do the reactants have more energy that the products in an exothermic reaction?
The difference between the energy of the reactants and the energy the products tells us the energy that has been released to the surroundings
What does the difference between the energy of the reactants and the energy the products tell us?
Endothermic reactions are reactions that take in energy from their surrondings
What are endothermic reactions?
In an endothermic reaction the temperature of the surroundings decreases
What happens to the temperature of the surroundings in an endothermic reaction?
An example of a endothermic reaction is thermal decompostion
Give an example of endothermic reactions
Endothermic reaction are used in cold packs and cooking
What are two uses of endothermic reactions?
What is the energy profile diagram for a endothermic reaction
In an endothermic reaction the products have more energy that the reactants
In an endothermic reaction what has more energy the reactants or the products?
In an endothermic reaction the products have more energy that the reactants because energy has been taken in from the surroundings
Why do the products have more energy that the reactants in an endothermic reaction?
The difference between the energy of the reactants and the energy the products tell us the amount of energy taken in by the reaction
What does the difference between the energy of the reactants and the energy the products tell us?
Reactions can only occur when particles collide with each other with sufficient energy
What is needed for reaction to occur?
Activation energy is the minimum amount of energy that particles need in order to react
What is the activation energy?
Where is the activation energy located on a energy profile diagram?
In an exothermic reaction energy changes are shown as negative
In an exothermic reaction energy changes are shown as positive or negative?
In an exothermic reaction energy changes are shown as negative because energy has been transferred
Why are energy changes shown as negative in exothermic reactions?
In an exothermic reaction energy changes are shown as postive
In an endothermic reaction are energy changes shown as positive or negative?
In an endothermic reaction energy changes are shown as positive because energy has been gained
Why are energy changes shown as positive in endothermic reactions?
Making bonds releases energy so it is exothermic
Is making bonds exothermic or endothermic?
Breaking bonds requires energy so it is endothermic
Is breaking bonds exothermic or endothermic?
The energy value tells us the energy required to break that bond
What is the energy value?
To calculate the energy of a reaction you need two things the structure of the molecules and the energy value of each bond, add up the energy need to break all the reactants and the energy need to make all the products, the difference between the energy needed for the reactants and the energy needed for the products is the energy change
How do you calculate the energy change of a reaction?
An electrolyte is a solution that can conduct electricty
What is an electrolyte?
An example of an electrolyte is an ionic compound
Give an example of an electrolyte
One way of producing electricity is to take two different metals and place them into an electrolyte
What is one way of producing electricity?
A battery is made up of two or more cells joined together
What is a battery made up of?
You can make a cell by joining two metals together by a wire and dipping them into a salt solution
How can you make cells?
In the cell, electrons will flow through the wire from the more reactive metal to the less reactive metal, the flow of electrons is an electric current which will flow in the circuit until one of the reactants is used up
What happens after you have dipped the two metals into a salt solution?
The greater the difference in reactivity between the two metals, the higher the voltage produced
What is the link between the reactivity between the two metals and the amount of voltage produced?
The more reactive metal has a higher tendency to give away electrons and form positive ions
What effect does the reactivity of a metal have on the tendency to give away electrons and form positive ions?
The voltage produced in a cell depends on the electrolyte
What does the voltage produced in a cell depend on?
When the reactants run out in non-rechargeable cells, the cell stops working
What happens to non-rechargeable cells when the reactants run out?
Hydrogen fuel helps to reduce global warming because the reaction doesn't produce carbon dioxide, the only product is water
How can using Hydrogen fuel reduce global warming?
- Petrol is cheaper than Hydrogen
- Petrol engines are more refined and less noisy
Give two pros for using Petrol
- When petrol burns it releases carbon dioxide which is harmful for the environment
- Petrol isn't renewable and so will eventually run out
Give two cons for using Petrol
- No vehicle emissions other than water vapour
- Hydrogen is can be made from renewable energy
Give two pros for using Hydrogen
- Hydrogen fuel cars are really expensive
- Hydrogen fuel cars needed to be charged more often than petrol cars
Give two cons for using Hydrogen
2H₂ → 4H⁺ + 4e⁻
What is the half equation for a negative electrode?
O₂ + 4H⁺ + 4e⁻ → 2H₂O
What is the half equation for a positive electrode?
2H₂ + O₂ → 2H₂O
What is the overall equation?