States of matter and mixtures.1 Flashcards
What’s an element
Substance that consists only of atoms with the same atomic number
Same protons in nucleus
What’s a compound
Substance that consists of atoms of two or more different elements chemically joined together
What does an element exist as
Atoms or molecules
What does pure mean
Substance contains only one element or compound
Gas to solid
Deposition
Solid to gas
Sublimation
What happens during a state change
Energy is transferred to or from the particles
The arrangement of particles changes
The movement of particles changes
What type of mixture can be seperated by simple distillation
A solvent from a solution
Water from sea water
What’s the function of a condenser in distillation
To cool the vapour
To turn it from the gas state to the liquid state
What’s the physical propert allowing substances to be seperated
Different boiling points
Describe temperature gradient in a fractionating column
Hottest at bottom and coldest at top
What do you use fractional distillation to separate
A liquid from a mixture of miscible liquids
(Liquids that mix completely with each other)
Ethanol from water and ethanol
What do you use filtration for
To seperate an insoluble substance from a liquid or a solution
Why would you use filtration?
To purify a liquid or solution by removing any impurities
Seperate solid you want from liquid it is mixed with
How does filtration work
Filter paper has tiny pores
Allows dissolved substances
Doesn’t allow insoluble solid particles going through
What does decanting mean
Pouring the liquid away carefully so that the solid stays behind
Why do you use crystallisation
To produce solid crystals from a solution
What happens in crystallisation
Solution is heated to remove enough solvent to produce a saturated solution (one that cannot hold any more solute)
Saturation solution is allowed to cool
Crystals form
Crystals seperated from liquid and dried
Explain crystallisation
Solubility is the mass of solute that dissolved in a given volume of solvent at a given temperature
Crystallisation works because
The solubility of the solute decreases as the saturated solution cools
Crystals from from the excess solute
Why’s paper chromatography used
To Seperate mixtures of soluble substances
Equipment for paper chromatography
Lid to stop evaporation of solvent Paper Drops of different samples Solvent Solvent front Different compound More soluble compounded
Explaining chromatography
Two phases:
A stationary phase (substance that does not move)
Mobile phase (substance that moves through the stationary phase - the solvent)
What happens during chromatography
Each soluble substance in the mixture forms bonds with the two phases
Substances that form stronger attractive forces with the stationary phase stay near the bottom
Substances that form stronger attractive forces with the mobile phase move towards the top
Why would you use a chromatogram
To distinguish between our and impure substances
Identify a substance by comparing patterns of spots
Identify substances using Rf values
