C10 Chemical Analysis Flashcards
What is a pure substance
A substance that is made up of just one substance. That substance can be either an element or compound.
What are the fixed points of an element or a compound
The melting and boiling points of the element/compound
What is an impure substance
A mixture of two or more different elements or compounds.
What can melting and boiling points do
Distinguish pure substances (fixed points) from mixtures (no fixed points)
What are formulations
Useful mixtures, made up in definite proportions, designed to give a product the best properties possible to carry out its function
Step 1 of chromatography practical
Use a pencil to draw a horizontal base line, 1 cm from the bottom of the paper.
Step 2 of chromatography practical
Use a pencil to draw a cross on the centre of the base line.
Step 3 of chromatography practical
Use a capillary tube to add some of the food colouring onto the cross and allow to dry.
Step 4 of the chromatography practical
Fold the top edge of the chromatography paper over a wooden splint and keep in place with a paper clip.
Step 5 of chromatography practical
Add 0.5 cm depth of water into the beaker.
Step 6 of chromatography practical
Carefully put the chromatogram into the beaker and leave until the solvent front is past the last coloured spot.
Step 7 of chromatography practical
Remove the chromatogram. Using a pencil, mark the solvent front and the coloured spots. Allow the chromatogram to dry.
What happens when you apply a lighted splint to hydrogen gas
Hydrogen gas burns rapidly with a squeaky ‘pop’
What does oxygen gas do to a glowing splint
Relights it
What happens when carbon dioxide reacts with limewater
The limewater turns milky (cloudy)
What happens when chlorine gas reacts with damp blue litmus paper
It bleaches it white.
Limitations of the particle model
Atoms are mostly empty space, so they aren’t solid spheres and they can vary in size.
Structure of compounds
-Fixed composition
-Chemical reactions are needed to separate the elements in a compound
-There are chemical bonds between the atoms of different elements in a compound.
Structure of mixtures
-No fixed compositions
-Can be separated through physical means
-No chemical bonds between atoms
Ways mixtures can be seperated
Filtration, crystallisation, distillation
What is filtration
Funnel leading into a beaker separates a mixture of salt, sand and water, the sand (residue) is collected in the funnel and the salt solution (filtrate) passes through to the bottom.
What is crystillisation
Beaker is place on top of a stand, under the stand, a bunsen burner provides heat. The beaker is filled with water and on top of the beaker there is a salt solution the water condenses upwards. It ends up crystallising chloride from its solution in water.
What is distillation
A salt solution is put inside a round bottom flask which is on a stand and has a bunsen burner under it, the water boils and rises at 100°c, it then passes through a condenser which cools the steam back into pure water which is collected. This process distills pure water from salt solution
Miscible meaning
Able to mix
What is the boiling point of ethanol
78°C
What is chromatography
The paper record of separation.
What is fractional distillation effective for
Separating miscible liquids
Why is separation possible in fractional distillation
Due to the different boiling points of the liquids in the mixture.
How does chromatography allow separation
Different substances are separated due to their different solubilities in the solvent used.
