Mocks Flashcards
What is a compound?
An atom can be chemically combined with other atoms to make a compound.
What is an atom?
An atom is the smallest piece of an element that can exist.
What is an element?
A substance that cannot be broken down into any other substance.
There are 118 different types of elements that humans have discovered, each of which has its own chemical symbol.
Give at least 2 key features of a chemical reaction.
Compounds are broken up or formed.
At least 1 new substance is created.
Measurable energy change.
No atoms are created or destroyed.
What is a mixture?
Mixtures are made up of at least 2 substances (elements or compounds) that have not been chemically combined.
What gases can be found in air?
Nitrogen
Oxygen
Argon
Carbon dioxide
Can mixtures be separated?
Yes
What is chromatography?
The mobile phase (a liquid or gas), moves through the stationary phase, carrying the components of the mixture along with it.
Helps us to analyse and identify the different things in the mixture.
What is filtration?
Filtration separates mixtures that contain insoluble solids (can’t dissolve) and soluble liquids (can be dissolved).
What does crystallisation seperate?
A soluble substance from a solvent.
What is distillation?
Distillation is a special technique used to separate mixtures of liquids. It uses the different boiling points of liquids to separate them.
What are the two different types of distillation?
Simple and fractional
Why is a thermometer used in simple distillation?
Makes sure the highest boiling point is not exceeded, otherwise both liquids would boil and the process would not separate them.
J.J. Thompson (in 1897) discovered what?
ELECTRONS.He modelled the atom as a ‘plum pudding’ - a ball of positive charge (dough), with negatively charged electrons (currants).
Ernest Rutherford (1909) discovered what?
That alpha particles could bounce back off atoms.
An atom’s mass is concentrated in the nucleus and contains positively charged particles called PROTONS.
Niels Bohr discovered what?
Electrons orbit the nucleus at fixed distances.
James Chadwick (in 1932), discovered what?
Some particles in the nucleus have no charge. He called them NEUTRONS.
What is the overall charge of an atom?
Neutral.
What is the overall charge of the nucleus?
Positive.
What is the number of protons equal to?
The number of electrons.
How to find out the number of protons?
Atomic number
How to calculate the number of neutrons?
Atomic mass - atomic number
What is an isotope?
Atoms with the same number of protons but different numbers of neutrons.
Name the 3 hydrogen isotopes:
Protium
Deuterium
Tritium
What is the equation for relative atomic mass?
Isotope abundance x isotope mass number
————————————
Isotope abundances
What does the isotope abundance tell us?
How often each different isotope of an element is found.
Outer shell =
Electron shells =
Outer shell g (ground number)
Electron shells p (period number)
Who was John Newland?
The first chemist to devise a periodic table.
It was ordered by the mass of the element.
But, it was incomplete and some elements were placed in inappropriate groups.
Dimitri Mendeleev’s periodic table was good because…
Mendeleev recognised that there may be undiscovered elements.
He added gaps to Newlands’ table to account for undiscovered elements.
Mendeleev even predicted the properties and masses of these undiscovered elements.
Give 2 properties of metals:
High melting points
High boiling points
Good conductors of heat + electricity
Metals are all solids (except for mercury) at room temperature.
Give 2 properties of non-metals:
Lower melting points than metals.
Lower boiling points than metals.
Often found as gases.
Generally do NOT conduct heat or electricity
The discovery of what proved Mendeleev’s periodic table to be correct and Newlands’ to be wrong?
Protons and isotopes
What name is given to group 0?
Noble gases
Give 2 properties of noble gases:
Unreactive (inert)
Low boiling points
Low density
Exist as single atoms
Colourless
What name is given to group 7?
Halogens
What is a displacement reaction?
When a more reactive element displaces (or pushes out) a less reactive element from a compound that contains it.
Give 2 properties of halogens:
7 electrons on outer shell
Very reactive
Get less reactive down group
Diatomic molecules
Form salts
What name is given to group 1?
Alkali metals
What colour flame does…
- Lithium
- Sodium
- Potassium
burn with when it reacts with oxygen?
Lithium = crimson flame
Sodium = yellow/ orange flame
Potassium = lilac flame
Reactions of alkali metals:
- with water
- with chlorine
- with oxygen
with water = metal hydroxides
with chlorine = metal chlorides
with oxygen = metal oxides
Give a key feature of a chemical reaction:
At least 2 new substance is created
An energy change can be measured
Compounds are broken up or formed
What is the relative mass of a:
- proton
- neutron
- electron
proton = 1
neutron = 1
electron = 0.0005 (rounded to 0)
Give 2 transition metal properties:
Higher melting points
Higher density
Lower reactivity
Can form colourful compounds
Can form ions with different positive charges
Are often used as catalysts
What is a molecule?
A group of at least 2 atoms held together by attractive forces known as chemical bonds
Name of Rutherford’s model?
Nuclear model
What is ionic bonding?
Attraction between oppositely charged ions.
What is covalent bonding?
2 atoms sharing 1 or more pairs of electrons.
What is metallic bonding?
Attraction between positively charged ions and negatively charged delocalised electrons.
What are ions?
Charged particles that form when an atom or molecule either loses or gains electrons.
Positive ions are created when an atom/ molecule _____ electrons.
Negative ions are created when an atom/ molecule _____ electrons.
loses
gains
What is another name for negative ions?
Anions
What is another name for positive ions?
Cations
What are delocalised electrons?
Delocalised electrons are NOT bound to an atom and are free to move around within the lattice.
What is a limitation if the ‘simple sphere’?
Forces between particles are not shown.
Shows particles as spherical
Portrays particles as solids
The amount of energy required for substances to change state depends on the strength of the forces between their particles.
What are strong forces?
Strong forces between particles means a lot of energy is needed to overcome them.
Substances with strong for es between particles have high melting and boiling points.
The amount of energy required for substances to change state depends on the strength of the forces between their particles.
What are weak forces?
Weak forces between particles means little energy is needed to overcome them.
Substances with weak forces between particles have low melting and boiling points.
What are the four state change processes?
Freezing, melting, boiling, condensing
What are the four state symbols?
(g)
(l)
(s)
(aq) aqueous solutions… substances dissolved in water.
What is sublimation?
Conversion of a substance from the solid to a gas without becoming a liquid
What are Ionic compounds?
They form giant ionic lattice structures, which are held together by strong electrostatic forces between ions with opposite charges. These electrostatic forces are called ionic bonds.
Give a property of ionic compounds:
High melting points
High boiling points
Don’t conduct electricity if solid
Conduct electricity if liquid or in a solution
What are small molecules?
Individual small molecules are held together by intramolecular bonds (covalent bonds which are very strong). Numerous small molecules can be held together by intermolecular forces (very weak and easy to break).
What are polymers?
Large, chain-like molecules that can extend for thousands of atoms.
What are polymers held together by?
Strong covalent bonds between atoms in molecules.
Weak intermolecular forces between molecules.
Because of the large size of polymer molecules, the intermolecular forces add up to be quite strong.
What is diamond structure?
A giant covalent structure.
What is an alloy?
A combination of 2+ elements, where at least 1 is a metal.
Why are metals good conductors of electricity and heat?
Their delocalised electrons can carry a charge/ heat energy within the structure.
Diamond is an allotrope (form) of carbon. Diamond has the following properties: (name 2)
High melting point
Hard
Does not conduct electricity because there are no delocalised electrons
Graphite is an allotrope (form) of carbon. Graphite has the following properties: (give 2).
Soft
Conducts electricity
Graphene is an allotrope (form) of carbon. Graphene has the following properties: (give 2).
Conducts electricity
Light but strong
What are fullerenes?
Molecules of carbon atoms that take up hollow structures. Their structure is usually carbon atoms arranged in hexagonal (6-sides) rings, but pentagonal (5-sided) and heptagonal (7-sided) carbon rings can also be found.
What was the first fullerene discovered?
Buckminsterfullerene
Give a use of spherical fullerenes:
Catalysts
Lubricants
As vehicles for transporting drugs into our bodies
Give 1 use of cylindrical fullerenes:
Electronics
Nanotechnology
For strengthening materials (e.g. tennis racket frames)
What is Graphene?
A single layer of graphite.
Name 3 uses of nanoparticles:
Catalysts
Medicine
Electronics
Cosmetics
Deodorants
Smaller objects have ______ surface area to volume ratios.
greater
Formula for number of moles?
Mass/ relative formula mass
What is the formula for concentration (g/dm3)
Mass (g)/ volume (dm3)
What is OIL RIG?
Oxidation Is Losing [electrons]
Reduction Is Gaining [electrons]
What name do we give to highly unreactive metals found in the Earth’s crust?
Native metals
How does sodium react with water?
Fizzes rapidly and melts to form a ball that moves around on the water surface
How does potassium react with water?
The hydrogen produced ignited instantly and the metal also sets alight, sparking and burning with a lilac flame.
How does lithium react with water?
Fizzes steadily and floats, becoming smaller until it eventually disappears.
What is the neumonic for order of reactivity?
People
Sometimes
Catch
Monkeys
And
Crazy
Zebras
In
Large
Heavy
Cages
What is the aim of the required practical - separating mixtures?
The aim of this practical is to produce a pure, dry sample of a soluble salt from an insoluble oxide or carbonate.
Here is the method for the required practical - separating mixtures:
1) Preparation - gently warm an acid using a Bunsen burner. Add the insoluble solid (with stirring) until no more reacts.
2) Filtration - filter the solution to remove excess insoluble solid. This will leave a solution of the salt dissolved in water.
3) Crystallisation - heat the solution in an evaporating basin above a beaker of water. The ‘water bath’ ensues gentle heating. Leave the solution to cool and allow more water to evaporate. As water evaporates, the solution will become more concentrated and the salt will begin to crystallise.
What is electrolysis?
The process that splits ionic compounds into the different elements that they are made of.
What is a disadvantage of electrolysis?
-> Lots of energy is needed to:
- melt the solid ionic compound to slow the ions to flow.
- Produce the electrical current.
-> All this energy costs money.
What is an electrolyte?
An ionic compound that produces a solution that conducts electricity when dissolved in water.
What happens during an endothermic reaction?
Energy from the surroundings is transferred to the reacting chemicals, causing the temperature of the surroundings to decrease.
Give an example of an endothermic reaction:
Photosynthesis
Electrolysis
Ice packs
What happens during an exothermic reaction?
Energy from the reacting chemicals is transferred to the surroundings, which often increase temperature as a result.
Give an example of an exothermic reaction:
Combustion
Neutralisation
Oxidation
Hand warmers
What are the two requirements for a reaction to happen?
Collisions - particles of the reactants have to collide.
Activation energy - collisions that happen between particles of the reactants must take place with enough energy.
