March Mocks Flashcards
Definition of Element?
A substance made up of atoms that all contain the same number of protons (one type of atom) and cannot be split into anything simpler.
What is a Pure Substance?
Contains only one substance, with no other substances mixed together
Why does a Mixture’s boiling point vary?
Has a range of melting and boiling points as they consist of different substances that melt or boil at different temperatures
On a Chromotography Paper, would a more soluble dye be higher up or lower down on the paper?
Higher Up
Rf equation?
Rf value = distance moved by compound ÷ distance moved by solvent
Definition of an Atom?
The smallest particle of an element that consists of electrons surrounding a nucleus that contains protons and neutrons.
Definition of a Molecule?
A cluster of non metal atoms that are chemically bonded together
RAM?
Weighted average mass of one atom of an element, taking into account the abundances of all the isotopes of that element.
Ar equation
(% of Isotope 1 x mass of Isotope 1) + (% of isotope 2 x mass of isotope 2)/100
Definition of Simple Molecular Structure?
Consists of molecules in which the atoms are joined by strong covalent bonds.
Melting and Boiling Point of Simple compounds in relation to Molecular Mass:
As the relative molecular mass of a substance increases, the melting and boiling point will increase as well (positive correlation).
An increase in the relative molecular mass of a substance means that there are more covalent bonds in the structure, so there are more intermolecular forces of attraction that need to be broken down.
So larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
Melting and Boiling Point of Simple compounds in relation to Molecular Mass:
The relative molecular mass of a substance and the melting and boiling point are directly Proportional
An increase in the relative molecular mass of a substance means that there are more covalent bonds in the structure, so there are more intermolecular forces of attraction that need to be broken down.
So larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
Giant Covalent Structure
Non-metal atoms
joined to adjacent atoms by covalent bonds
forms a giant lattice structure.
Allotropes
Different atomic, molecular arrangements of the same element in the same physical state.
Properties of Carbon?
Hard
Each carbon atom is joined to four other carbon atoms, forming a giant covalent structure.
Strong covalent bonds are difficult to break.
High Melting and Boiling Point
Giant Covalent Structure so there are many strong covalent bonds that needs to be broken down.
Large amounts of heat energy is needed to overcome forces and break down bonds.
Does not Conduct Electricity
All four valence (outer-shell) electrons are used in covalent bonds so there are no delocalised electrons that are mobile to conduct electricity
Uses:
Cutting Tools
Jewellery
Properties of Graphite
Properties:
Soft and Slippery
Graphite is made up of two-dimensional layers of carbon atoms, which are held by weak van der Waal’s forces, lie on top of each other.
Forces of attraction between the layers are weak so the layers easily slide over one another and can easily be separated.
High Melting and Boiling Point
Within each layer, each carbon atom forms strong covalent bonds with three other carbon atoms in a giant covalent structure so there are many strong covalent bonds that needs to be broken down
Large amounts of heat energy is needed to overcome forces and break down bonds.
Conducts Electricity
Only three valence electrons are used in forming covalent bonds
Fourth electron is delocalised between the layers and free to move parallel to the layers to conduct an electric charge.
Uses:
Lubricant
Electrodes for Electrolysis
Properties of Fullerene?
Soft
Each carbon atom is joined to only three other carbon atoms so there are weak intermolecular forces of attraction between molecules.
Intermolecular bonds can be broken down easily making it soft.
Low Melting and Boiling Point
Each carbon atom is joined to only three other carbon atoms.
This means that there are weak intermolecular forces of attraction between molecules.
So small amounts of heat energy is needed to overcome forces and break down bonds.
Conducts Electricity
Only three valence electrons are used in forming covalent bonds.
Fourth electron is delocalised and is free to move to conduct an electric charge.
Uses:
Drug Delivery System in the Body (Nanotubes)
Lubricant
Catalyst
Explain the bonding of metallics?
Metal atoms are held strongly to each other by metallic bonding.
In the metal lattice, the atoms lose their valence electrons and become positively charged.
The valence electrons no longer belong to any metal atom and are said to be delocalised.
They move freely between the metal ions like a sea of electrons.
Electrolyte?
A liquid that conducts electricity.
How to conduct an experiment of electrolysis of lead bromide?
Add Lead (II) Bromide into a beaker and heat so it will turn molten, allowing ions to be free to move to conduct an electric charge.
Add two graphite rods as the electrodes and connect this to a power pack or battery.
Turn on power pack or battery and allow electrolysis to take place.
Negative bromide ions move to the positive electrode (anode) and lose two electrons to form bromine molecules. There is bubbling at the anode as brown bromine gas is given off.
Positive lead ions move to the negative electrode (cathode) and gain electrons to form a grey lead metal that deposits on the surface of the electrode.
Ionic Half equation for Oxygen?
2H2O - 4e- –> O2 + 4H+
Electrolysis of Aqueous Solutions?
Add Aqueous solution into a beaker.
Add two graphite rods as the electrodes and connect this to a power pack or battery.
Turn on power pack or battery and allow electrolysis to take place.
How to find the products of Aqueous Electrolysis
An investigation into the products formed at each electrode can be done:
If a solid forms around the electrode, the metal ions have been deposited. Colour can give away what metal.
If the gas produced at the cathode burns with a ‘pop’ when a sample is lit with a lighted splint. This shows that the gas is hydrogen.
If the gas produced at the anode relights a glowing splint dipped into a sample of the gas. This shows that the gas is oxygen.
Exothermic Reaction definition?
Reaction in which thermal energy is given out to the surroundings
Delta H = -
Examples of an Exothermic Reaction?
Burning
Neutralisation
Reaction between Water and Calcium Oxide
Endothermic Reaction definition?
Reaction in which thermal energy is taken from the surroundings
Examples of Endothermic Reactions?
Electrolysis
Thermal Decomposition of Copper Carbonate
Reaction between Ethanoic acid and Sodium Carbonate
How do we know something is endothermic
If more energy is absorbed than it releases, this reaction is endothermic
More energy is required to break the bonds than make the bonds
Energy Change equation?
LHS - RHS
Calorimetry experiment for neutralisation, dissolving and neutralisation?
Using a measuring cylinder, place 25 cm3 of solution 1 into a polystyrene cup
Measure and record the temperature of solution 1
Add a measured amount of reactant (solid for dissolving, solution 2 for displacement and neutralisation) into the polystyrene cup and stir the mixture
Measure and record the highest temperature reached by the mixture
Calorimetry experiment for Combustion?
Using a measuring cylinder, put 100 cm3 of water into a copper can
Measure and record the initial temperature of the water
Fill the spirit burner with test substance and measure and record its mass
Place the burner under the copper can and light the wick
Stir the water constantly with the thermometer and continue heating until the spirit burner burns out
Measure and record the highest temperature of the water
What happens when acids react in water?
they produce hydrogen ions (H+).
These H+ ions make the aqueous solution acidic.
Dissociation of HCL
HCl (aq) → H+ (aq) + Cl– (aq)
What are acids usually produced from?
Metal Oxides
What happens with Weak acids?
ionizes partially/incompletely in water. In this case they form an equilibrium between the acid and the ions in solution.
Acid + Metal Carbonate
Acid + Metal Carbonate → Salt + Carbon Dioxide + Water
Metal Oxide + Acid?
Salt + Water
Metal Hydroxide + Acid?
Salt + Water
Ammonia + Salt
Ammonium Salt + Water
Are Metal Oxides, Ammonia and Metal Hydroxides Insoluble or Soluble in Water?
Yes
Describe an experiment to prepare a pure, dry sample of a soluble salt, starting from an insoluble reactant
Add dilute acid into a beaker and heat using a bunsen burner flame
Add the insoluble base, a little at a time, to the warm dilute acid and stir until the base is in excess
Filter the mixture into an evaporating basin to remove the excess base
Heat the solution to evaporate water and to make the solution saturated.
Check the solution is saturated by dipping a cold, glass rod to the solution and seeing if crystals form on the end.
Leave the filtrate in a warm place to dry and crystallise
Decant excess solution
Blot crystals dry
How to make an Insoluble Salt from Soluble Reactants?
Dissolve soluble salts in water and mix together using a stirring rod in a beaker
Filter to remove precipitate from mixture
Wash filtrate with water to remove traces of other solutions
Leave in an oven to dry
How to make Copper Sulfate?
Add dilute sulfuric acid into a beaker and heat using a bunsen burner flame
Add copper (II) oxide (insoluble base), a little at a time to the warm dilute sulfuric acid and stir until the copper (II) oxide is in excess (stops disappearing)
Filter the mixture into an evaporating basin to remove the excess copper (II) oxide
Leave the filtrate in a warm place to dry and crystallize
Decant excess solution
Blot crystals dry
How to make Lead Sulfate
Dissolve Lead (II) Nitrate and Potassium Sulfate in water and mix together using a stirring rod in a beaker
Filter to remove precipitate from mixture
Wash residue with water to remove traces of potassium nitrate solution
Leave in an oven to dry
Characteristics of Lithium reacting with Water?
Reaction slower than Na
H2 gas
Lithium’s melting point is higher and heat isn’t produced quickly, so the lithium doesn’t melt
Observations when Na reacts with Water?
Melts around in a tiny ball that dashes around the surface
Floats on Water because its less dense
Melts because Sodium has a low melting point and a lot of heat is made in this reaction
Hydrogen is evolved which causes the ball of sodium to move around the surface of the water
What happens when Rubidium is reacted with Water?
Explodes with Sparks
What happens when Caesium is reacted with Water?
Violent explosion due to rapid production of heat and Hydrogen
Trend of Reactivity in Group 1?
Reactivity of group 1 metals increases as you go down the group.
Each outer shell contains only one electron, when group 1 metals react, they will lose one outer electron to get a full outer shell of electrons.
As you go down group 1, the number of shells of electrons increases by 1 (period number increases down the periodic table).
This means that the outer electron is further away from the nucleus so there are weaker electrostatic forces of attraction.
This requires less energy to overcome the electrostatic forces of attraction between the negatively charged electron and the positively charged nucleus.
This allows the electron to be lost easily, making it more reactive as you go down the group.
Alchohols
Family of organic (carbon-based) compounds that all contain the -OH group that is responsible for their chemical properties and reactions.