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