Chemical Analysis Flashcards
Define pure substance
A pure substance is a single element or compound (and is not mixed with any other substance.)
What is a compound
A substance that consists of two or more different elements chemically bonded together.
What is a mixture
A mixture is defined as two or more substances mixed together, which are usually easy to separate.
What is a element
An element is a substance that consists of only one type of atom. It cannot be broken down into anything simpler by chemical means
What is a melting point
The temperature at which solid changes state into a liquid
What is a boiling point
The temperature at which liquid turns to a gas.
Why can the purity of substances be determined by melting and boiling points?
Pure substances will give sharp boiling and melting points.
This is became it is pure and one type of compound or element meaning it will have a fixed temperature for melting and boiling. We see this on a graph when the temperature levels out.
What will the presence of an impurity change in melting and boiling points
Lowers melting points of solid
Raises boiling point of liquid.
What is a formulation
It is a mixture which has been designed as a useful product and is formed by mixing together several different substances in carefully measured quantities to ensure the product has the required properties.
Name common formulations
Alloys - mixture of or more element one is a metal.
Medicine - tablets have drugs along with corn starch and lubricant.
Fertilisers - contain mixtures of nitrogen, phosphorus and potassium compounds.
Define soluble
A soluble substance dissolves in water
Define insoluble
An insoluble substance does not dissolve in water
Define solute
A soluble substance which dissolves is the solute
Define solvent
The liquid in which the solute dissolves in is the solvent
Define solution
The mixture of solute dissolved in a solvent is a solution
Define miscible
Miscible liquids mix
Define immiscible
Immiscible liquids do not mix
Define filtrate
The filtrate is the filtered solution
Define residue
The residue is the solid which remains on the filter paper.
What is evaporation
The changing of state from liquid to gas
What is condensation
Changing of state form gas to liquid
What is sublimation
Changing of state from solid to gas
Name 5 separation techniques
Filtration
Evaporation
Crystallisation
Distillation
Chromatography
What is fractional distillation
It is used to separate 2 or more miscible liquids the boil at different temperatures. Uses a condenser to change gas back to liquid.
What is chromatography
It separates 2 or more soluble substances in a solution e.g food dyes and inks.
Define chromatography
The separation of mixtures of soluble substances by running a solvent through the mixture on the paper, which causes the substances to move at different rates over the paper.
What is a Rf value
A Rf (retention factor) value is a value that allows comparison of chromatograms if solvent and paper are the same.
Equation for Rf values
Distance moved by sample ➗ Distance moved by solvent.
Define potable
Potable water is water that is safe to drink
How is water made potable
- Filtration of large objects
- Sedimentation (aluminium sulfate added so dirt clumps together)
- Filtration made of fine sand, gets rid of any remaining particles or dirt.
- Chlorination kills all microorganisms
- pH adjustment so water is neutral.
Define desalination
It is the process of removing dissolved substances from the sea water.
How is sea water made potable
Distillation, sea water is boiled and water is condensed.
