Chapter 6 - Chemical analysis Flashcards
What is a pure substance ?
A pure substance is a single element or compound not mixed with any other substances
Give some examples of pure substances
Diamond, water, tables salt.
What does the term melting point mean ?
Melting point is the temperature at which a solid changes into a liquid
What does the term boiling point mean ?
Boiling point is the temperature at which a liquid changes into a gas
What is unique about pure substances melting and boiling points ?
Pure substances have a sharp, specific melting and boiling point
What is unique about mixtures melting and boiling points ?
melt or boil over a range of temperatures
also has a lower melting point and a higher boiling point
What is a formulation ?
A formulation is a mixture that has been designed as a useful product.
How is a formulation formed ?
It is formed by mixing together several different substances in carefully measured quantities
What is a mixture ?
A mixture is defined as two or more substances mixed together
What is a solute ?
A solute is the substance that dissolves in a solvent
What is a solvent ?
A solvent is the liquid in which a solute dissolves
What is a solution ?
A solution is a solute dissolved in a solvent
What is a soluble substance ?
A soluble substance is one which will dissolve in a solvent
What is a insoluble substance ?
An insoluble substance is one which will not dissolve in a solvent
What is filtration used to separate ?
An insoluble solid from a liquid
What is filtrate ?
The liquid that passes through the filter paper during filtration is called the filtrate.
What is residue ?
The solid that remains on the filter paper after filtration is called residue
What is evaporation used to separate ?
A dissolved solid from a solvent.
What is evaporation ?
Evaporation is the change of state from a liquid to a gas when heated.
What is another way of separating an dissolved solid in a solute ?
crystallisation
What is a saturated solution ?
A saturated solution is one in which no more solid can dissolve at that temperature
What does simple distillation separate ?
It separates a solvent from a solution.
What is condensation ?
condensation is the change of state from a gas to liquid when cooled
What are anti-bumping granules ?
anti-bumping granules are added to the mixture in the flask to promote smooth boiling
What is distillate ?
The distillate is the liquid that is cooled from vapour and collected during distillation
What is the basic process of simple distillation ?
Evaporation followed by condensation
What is fractional distillation used to separate ?
Fractional distillation is used to separate miscible liquids which have different boiling points
What is a miscible liquid ?
miscible liquids are liquids that mix together
What are immiscible liquids ?
immiscible liquids are liquids which do not mix together but form two distinct layers
How does fractional distillation work ?
- the mixture of liquids is heated up
- each boil and turn into a gas at different temps
- each vapor rises up is condensed and collected
- each separate distillate is called a fraction
What is chromatography used to separate ?
mixture of soluble substances in a solution
What is the solvent font ?
The solvent font is the furthest travelled by the solvent
How many spots does a pure substance produce in chromatography
1
What are the stationary and mobile phases of chromatography ?
stationary phase : paper
Mobile : solvent
What factor affects the speed that a solvent travels up the paper ?
substances that have a higher attraction to the paper move slowly and only travel a short distance.
substances that have a high attraction to the solvent are more soluble in it and will travel up the paper quicker
What is the equation to find Rf values ?
distance moved by substance
Rf = ——————————————–
distance moved by solvent
What is potable water ?
Potable water is water that is safe to drink
What three processes water must go through to become potable ?
- filtration
- sedimentation
- chlorination
Explain how (potable water) filtration is carried out
water is sprayed onto specially designed layers of sand/gravel called filter beds. insoluble solids are removed as the water trickles through them.
Explain how sedimentation is carried out
aluminium sulfate is added to clump tiny particles together to make larger particles, then it is passed through a fine filter such as carbon granules yo remove very small particles
Explain how chlorination is carried out
Chlorine gas is bubbled into the water to kill microbes and sterilise the water
What is desalination ?
Desalination is the process of removing dissolved substances from sea water
How is desalination usually carried out ?
Usually carried out by distillation
What is the process of desalination ?
It requires large amounts of energy to boil the water, which makes it very expensive.
