Unit1Topic1 - Elements, Compounds and Mixtures Flashcards
Definition of an element
An element is a substance that consists of only one type of atom. Elements cannot be broken down into simpler substances by chemical means.
Definition of a compound
A compound is a substance that consists of two or more different elements chemically bonded together.
Definition of a mixture
A mixture consists of two or more substances that are usually easy to separate.
Appearance Magnetic?
Iron filings …. ….
Sulfur …. ….
Iron and sulfur mixture …. ….
Iron sulphide …. ….
Appearance Magnetic?
Iron filings Grey solid Attracted
Sulfur Yellow solid Not attracted
Iron and sulfur mixture Grey and yellow solid mix Iron yes sulfur no
Iron sulphide Grey-black solid Not attracted
Soluble definition
A solid that dissolves easily in a liquid solvent e.g. sugar, salt
Insoluble definition
A solid that does not dissolve easily in a liquid solvent e.g. sand
Solute definition
A solid that dissolves. This is a substance that changes its state during a dissolving process i.e. the substance that dissolves e.g. sugar, salt
Solvent definition
This is a substance that does not change its state during a dissolving process i.e. the substance in which the solute dissolves e.g. water
Solution definition
A mixture containing the solute and solvent
Residue definition
Solid particles trapped in filter paper e.g. sand
Filtrate definition
Liquid particles that pass through the filter paper
Distillate definition
The liquid that condenses during distillation and is collected
Miscible definition
A liquid that mixes easily in another liquid e.g. ethanol and water
Immiscible definition
A liquid that does not mix easily in another liquid e.g. oil and water
What is filtration used for?
Used to separate an insoluble solid from a liquid e.g. sand and water
What is evaporation/crystallisation used for?
Used to separate a solute from a solvent e.g. salt and water
What is the separating funnel used for?
Used to separate two immiscible liquids e.g. oil and water
Steps involved in paper chromatography
(1) spots of dye solutions are put along the base line of a sheet of filter paper
(2) the filter paper is put into a beaker containing a small volume of solvent
(3) the solvent slowly rises up the filter paper and when the solvent has nearly reached the top of the filter paper it is removed and dried
What is simple distillation used for?
Used to separate a liquid solvent from a solution e.g. separating water from copper sulfate solution
What is fractional distillation used for?
Used to separate miscible liquids e.g. ethanol and water
Boiling point of ethanol
78oC
What is mass spectrometry used for?
To determine RAM/RMM
Predict what value you would expect to find a peak at for ethanol C2H5OH
(2x12) + (5x1) + (1x16) + (1x1)
= 24+5+16+1
=46
By carefully interpreting data from mass spectrometry we can deduce…
- the RAMs of elements
- the no. of isotopes an element contains
- the RMMs of compounds and molecules
What is high performance liquid chromatography (HPLC) used for?
To determine the no. of components in a mixture
Where is gas liquid chromatography used?
In the petrochemical industry, environmental monitoring and in chemical research
Benefits of using mass spectrometry
- identification of unknown elements or compounds
- fast analysis
- results can be linked to database to identify substance
- small sample
Drawbacks of using mass spectrometry
- destroys sample
- expensive
- presence of isotopes leads to more than one peak
Benefits of using HPLC
- fast
- accurate
- use only minute samples
Drawbacks of using HPLC
- sample must be liquid
- expensive
- lack of sensitivity
- trained staff required to operate it
