C1- Atomic structure Flashcards
define the (relevant) group names
1: alkali metals
2-3 (not including 2 or 3 ) transition metals
7: halogens
0: Noble Gases
define:
element:
compound:
mixture:
element: pure substance made up of only one type of element
compound: pure substance made up of 2 or more different elements chemically bonded
mixture: combination of two or more substances (elements or compounds) that aren’t chemically joined but physically mixed together
describe how filtration works as a method of separating mixtures
Insoluble Solid: The solid being separated must be insoluble in the liquid.
Filter Paper: A porous material that allows liquids to pass through but not solids.
Funnel: Holds the filter paper and directs the liquid into a container.
Filtrate: The liquid that passes through the filter paper.
Residue: The solid that is left behind on the filter paper
what is crystallisation
Crystallisation is the process of forming solid crystals from a solution by allowing the solvent to evaporate slowly ( heat up solution in an evaporating basin above a bunsen burner, then rest of solvent is left to evaporate in petri dish at room temp)
what is distillation and how does it work?
Distillation is used to seperate a soluble solid from a solvent and is often used in poorer countries to obtain pure water from sea water.
How it works:
- solution is heated and boiled to evaporate solvent
- vapour enters a condenser
-it cools and condenses back into a liquid and is collected in a receiving vessel
- solute remains in heated flask
fractional distillation, how it works and why:
used to separate miscible liquids ( combined completely) using their different boiling points though they can often be similar
how:
- ethanol has boiling point of 78 degrees
water has boiling point of 100 degrees
- the mixture is heated above a bunsen burner and predominantly the ethanol evaporates but due to close boiling point, some water may also evaporate
-to prevent the water vapour entering the condenser, a fractionating column of glass beads is put in place
- the temp is higher at the bottom and lower at the top of the column so as the vapour of the liquid with the higher boiling point rises, it will collect and condense on the glass beads whilst the liquid with the lower boiling point will pass over into the condenser
how do you test ( with a mixture of ethanol and water ) that there is no water remaining?
ethanol is flammable so if you apply a lighted splint, the distillate will burn with a blue flame unless there is an excess of water present
What is paper chromatography?
It is used to separate and identify substances from mixtures in a solution. It works because some compounds in a mixture will dissolve better than others in a solvent
How does paper chromatography work?
- take a piece of filter paper and use a pencil to draw a line at the bottom of the sheet ( baseline)
- dab a spot of the solution on the baseline
- put filter paper upright in a beaker containing a solvent but making sure not to submerge pencil line
- then wait for solvent to seep up the paper and the relative solubility of the components making up the mixture will determine how far they travel up the paper
- if any components aren’t soluble, they’ll remain on baseline
- leave to dry and pattern left is called a chromatogram
Why do the different components of the mixture move up the filter paper at different rates?
mobile phase: solvent that moves through the paper carrying different substances with it
stationary phase: the filter paper
the less soluble component is more attracted to the stationary phase and therefore, travels less distance
the more soluble component is more attracted to the mobile phase and travels more distance
how do you know if a substance is impure or pure?
pure: a pure substance produces one spot on the chromatogram
impure: an impure substance, or mixture, produces two or more spots
Interpreting a chromatogram:
you can compare unknown substances with know substances- they are likely to be the same if:
- they produce the same number of spots which match in colour
- they have the same Rf value ( distance travelled by substance/ distance travelled by solvent )
why is mass conserved in a chemical reaction
. The Law of The Conservation of Mass: states that the total mass of the products formed in a reaction is equal to the total mass of the reactants; mass is neither created nor destroyed in a chemical reaction
what is the definition for the state symbol (aq) ?
aqueous solution- substance dissolved in water
balance this symbol equation:
_C2H5OH + _O2 -> _CO2 + _H2O
Why may mass appear to change in a chemical reaction?
. a gas may be formed during a chemical reaction which, if not contained, can be released into the surroundings and the mass of the products will therefore be different to the mass of the reactants
why do the properties of a mixture not vary from the elements they’re composed of where compounds do?
The chemical properties of a mixture remain the same as the elements composing them because they haven’t been chemically bonded and therefore maintain their individual properties hence why a mixture can be separated physically whereas a compound cannot
How can you use experimental data to define a compound from a mixture
Compounds have a distinct melting and boiling point whereas mixtures melt and boil over a range of temperatures. For example, H2O, a compound, has a distinct melting point of 0 degrees and a distinct boiling point of 100 degrees
what did John Dalton discover and when?
Date: start of the 19th century
Discovered the name ‘atom’ and that every organism was made of
atoms. Found out that atoms are spherical and were indivisible, cannot
be destroyed or created. Many of atoms create molecules. Atoms of the
same element are identical
what model did John Dalton compose?
the solid sphere
What did JJ Thompson discover and when?
date: 1897
Discovered the electron. Positively charged ball/ sphere with negatively
charged electrons scattered around, the electrons were discovered by
passing electricity through a cathode ray tube with gas.
What model did JJ Thompson compose?
the plum pudding model
what did Earnest Rutherford do and when?
Date: 1909-1911
Shot a beam of positively charged alpha particles at a thin sheet of gold foil. Some
particles were scattered and a few were deflected back
What did Earnest Rutherford prove with his experiment?
concluded that most of an atom’s mass is concentrated at the centre
called the nucleus. Those that went through but changed direction
were close to dense, positive nucleus, causing them to be repelled.
Those that rebounded showed there was a small dense nucleus. The
majority passing through showed there was a lot of empty space
