What is the relative charge of:
a) a proton
b) an electron
c) a neutron
a) proton= +1
b) electron= -1
c) neutron= 0
What are the relative masses of the three sub-atomic particles?
- proton= 1
- neutron= 1
- electron= virtually nothing
What is the radius of an atom and the nucleus of an atom?
- atom= 1 x 10-10
- nucleus= 1 x 10-14
What is an element?
An element is substance made up of only one type of atom
What is an ion?
an ion is an atom or element that has lost or gained electrons, therefore giving it a charge
True or False? Elements only contain atoms with the same number of protons.
True
What does the relative mass number of an element tell us?
the total number of protons and neutrons
What does the relative atomic number of an element tell us?
the number of protons
Define an isotope
An isotope is a form of an element with the same number of protons but a different number of neutrons
Define a molecule
A molecule is two or more atoms, held together by chemical bonds
What is the difference between mixtures and compounds?
A compound is two or more different elements that are chemically combined in fixed proportions bonds whilst a mixture is two or more elements that are not chemically joined
Before the discovery of the electron, what were atoms thought to be?
Tiny spheres that could not be divided
What did the discovery of the electron lead to and what did this model suggest?
The plum pudding model:
the atom is a ball of positive charge with
negative electrons embedded in it
Which scientist did the alpha particle scattering experiment and what conclusions could be made from the experiment?
Ernest Rutherford
- the mass of an atom in concentrated in the centre
- the atom is mostly empty space
- the nucleus was charged
What replaced the plum pudding model and how did Neil Bohr adapt the model?
The nuclear model
he suggested that electrons orbit the nucleus at specific distances; his theoretical calculations agreed with experimental observations
Who provided evidence of the neutron within the nucleus?
James Chadwick
What are the 5 methods that can be used to separate mixtures?
- Filtration
- Crystallisation
- Simple Distillation
- Chromatography
- Fractional Distillation
Describe when simple distillation is used and explain
Used to separate a liquid from a solution (with different boiling points) e.g. separating pure water from sea water
• Equipment-conical flask, thermometer, condenser, beaker, Bunsen burner
• The mixture is heated up so the liquid we want evaporates as it rises up the pressure will force it down the condenser and the vapor will cool and condense into a liquid that would flow into the beaker
Describe when fractional distillation is used and explain
used for separating mixtures of liquids with different boiling points
• equipment-fractionating column, conical flask condenser
- The mixture would be heated to the boiling point of the substance which has a lower boiling point, causing it to evaporate and rise up the fractionating column and pass into the condenser and cool into liquid that will flow into the beaker
- Same thing done again to heat the remaining mixture the next boiling point
Why can evaporation always be used to separate soluble solids from solutions?
some solids decompose when heated (thermal decomposition)
Describe and explain crystallisation
separates solutions into their different parts: dissolved solids(solutes) and liquids(solvents) & separates a soluble solid from a solution
• equipment: crucible(evaporation dish), tripod, Bunsen burner or water bath, heat proof mat, filter paper, funnel
- Place the solution into a crucible and heat it gently(a water bath would be appropriate)
- Once some of the solvent has evaporated and you can see crystals forming stop heating the solution
- Leave the solution to cool. As the solution cools more crystals will start to form (because solids are less soluble at colder temperatures)
- filter out the solution using filter paper and a funnel
- dry the crystals e.g. by leaving them somewhere warm.
Describe and explain filtration
used to separate insoluble solids and
liquids
• equipment- funnel, filter paper, beaker
- the mixture is poured through the filter paper
- the insoluble solid is trapped by the filter paper whilst the liquid runs through and is collected below
Describe and explain chromatography
used to separate solutions with a number of different solutes in the solvent
• equipment: filter paper, beaker, solvent(e.g.) water, pencil
- draw a line on the filter paper in pencil and place dots of ink along the line
- fill the beaker with the solvent but make sure it is below the pencil line
- as the solvent moves up the paper it carries the solutes with it (different solutes move at different speeds so they separate.)
How are the elements of the periodic table arranged?
The elements are arranged by atomic number
