Topic C1 - Experimental Techniques Flashcards
What is Paper chromatography?
Analytical technique for seperating and identifying mixtures of coloured compunds
What is a suitable solvent for chromatography?
Ethanol or water (Te spot of sample must be above the surface of the solvent
How does the solvent move up the paper in chromatohrapju?
Through capillary action
Why won’t a spot move in chromatography?
A spot will not move if it is insoluble in the solvent
Why would a substance move further in chromatography?
The substance/sample would have less mass and is higher in solubility
What locating agent would you need to see a substance that has no colour?
ninhydrin
What is the equation for the retention factor?
distance moved by the compound / distance moved by the solvent (solvent front)
What is the filtered liquid called that is collected at the bottom?
Filtrate
What is the solid separated in the funnel called?
Residue
What is the condenser called in distillation?
Liebig condenser
What is the column called that helps with purifying in fractional Distillation?
Fractionating column
How would you seperate ethanol from water?
The boiling point of ethanol is 78°C whereas water is 100°C
In food, what can purity help with?
Water purification ensures the safety of the drink and prevents diseases (like cholera or dysentery
In medical productions, what can purity help with?
Any impurities in the durgs might cause harmful side effects and affect the drug efficacy
What is one method of determining purity?
Looking at the melting point of a substance, all chemicals have a specific mpt/bpt under the specific conditions, and these are accurately known. If these points change under the same conditions, it means that theire is an impurity. For example, salt water, which ahs impurities of NaCl, has a higher boiling point than pure water.
Why do we use pencil for the base line?
Because pencil does not dissolve in the solvent
What different types of chromatography are there?
Paper, gas
What is chromatography used for?
It is used to identify, unknown substances from known. Pure and impure substances
What do you call the change of states from solid to liquid, liquid to gas, gas to liquid, liquid to solid, and finally solid to gas?
melting, boiling, condense, freeze, and sublimation
What is changing state?
Having enough energy to overcome forces of attraction
What is a pure substance?
Only contains one substance
What does adding impurities/alloying do?
It can change the properties of the these materials (raises the boiling point, lowers the melting)
What are alloys?
mixture of elements (usually metals), designed to have useful prperties for a certain purpose
What are the differences between pure substances and mixtures?
pure will melt/boill at a specific temp. Whereas mixtures will melt and boil over a range of temps.
What is decanting?
It is used to separate insoluble solid from liquids. It allows the solid to settle to the bottom and carefully pour off the liquid
What is filtering?
More general method for speperating solids from liquids. Insoluble material stays in filter paper. Liquid collected. Useful method as both the solid and the liquid can be collected in one process. Can be sped up by using vacuum pumps and a Buchner funnel
Describe the practical method of Crystallisation.
- Add a suitable solvent (eg. water). 2. Warm the mixture in the solven and stir. 3. Filter the mixture - insoluble stuff = residue and can be dried. 4. Filtrate then evaporated and allowed to crystallise.
Describe the practical method of distillation
- Liquid is evaporated/boiled off in a round bottomed flask. 2. Gas condensed by passing it down a water cooled condenser. 3. Collect as the distillate. *Note you can also separate the liquids from a mixture of two or more liquids these are miscible (can mix), and the liquids have different voiling points
In an experiment what is salt, water, salt and water at the beginning of the practical, and salt and water at the end of the practical.
Solute, Solvent, Solution, Saturated
What is an element?
contains only one type of atom
What is a mixture?
two/more substances that are not chemically joined. So they can be seperated and may have properties similar to what it is made of.
What is a compound?
Two/more elements chemically joined in a fixed ration, so they will have different properties to the elements they ae made of
What is a solute?
A substance that is dissolved in a solvent
What is a solute
A substance that dissolves a solvent
What is a solution?
A mixture of one/ more solutes dissolved in a solvent
What is the boiling point
The temprature in which a liquid turns into a gas
