3.1 INTRODUCTION + SEPARATING TECHNIQUES Flashcards
3 signs of a PHYSICAL change
- Creates no new substances
- Are usually easy to reverse
- Absorb or release small ammounts of energy
3 signs of a CHEMICAL change
- Creates new substances
- Usually difficult to reverse
- Absorb or release large amounts of energy
Chemical test for water
Anhydrous Copper(II) Sulfate turns from white to blue
Physical test for water
Pure water will boil at 100c
Define an element
A substance containing one type of atom only
Typical properties of metals
- High MP/BP
- Electrical conductors
- Malleable
- Shiny
Typical properties of non-metals
- Low MP/BP
- Electrical insulators
- Brittle
- Dull
Diatomic Molecules
Nitrogen, Oxygen, Hydrogen + Halogens
Define a compound
A substance containing more than one type of atom, chemically bonded together
Define a mixture
A substance containing more than one type of atom not chemically bonded together
How does the ammonium chloride tube illustrate diffusion
- Ammonium chloride forms as a white smoke towards the hydrogen chloride end
- The hydrogen chloride molecules are heavier so diffuse slower compared to ammonia
- Heating the tube will speed up the reaction but not change the results
Define solute
The substance which is going to be dissolved
Define solvent
The liquid which is going to do the dissolving
Define solution
The resulting mixture of a solute dissolved in a solvent
Define saturated
A solution in which no more solute can be dissolved
Define suspension
A solid floating in a liquid because it cannot dissolve
Define soluble
A substance which can be dissolved
Define insoluble
A substance which cannot be dissolved
How is solubility measured
- g / 100g solvent
- You can use it as a ratio and scale it up and down
How do solubility curves work
- Measures solubility compared to temperature
- Below the line = soluble
- On the line = saturated
- Above line = insoluble
How do you carry out a chormatography experiment
- Draw a line near the bottom of the paper in pencil - as it won’t dissolve in the solvent
- Add spots of different dyes at regular intervals
- Place paper in beaker of solvent - with solvent below pencil line, so inks don’t dissolve into solvent
- Place lid on beaker - to stop solvent evaporating
- Allow solvent to move up paper until it is just below the top
- Take paper out and mark solvent front
- Allow paper to dry
How do you carry out paper chromatography
- Draw a base line in pencil at the bottom of the chromatography paper - so it doesn’t dissolve in solvent
- Add spots of dye on line in different inks
- Place paper in beaker of solvent - ensure below solvent line so it doesn’t dissolve into solvent
- Place lid on beaker - to prevent solvent evaporating
- Allow solvent to move up paper, until it is near the top
- Take the paper out and mark solvent front
- Allow paper to dry
What happens to soluble dyes in chromatography
They will move further up the paper
What happens to soluble dyes in chromatography
They will move further up the paper
What happens if a dye is insoluble in chromatography
It will not move from the baseline
In terms of physical properties, what is the differance between a pure substance and a mixture
A Pure substance has a fixed boiling point, but a mixture may melt/boil over a range of temperatures
What is filtration used for
To seperate a solid from a liquid
Describe how to carry out filtration
- Place filter paper in funner and pour in solution
- Residue is substance left in filter paper
- Filtrate is liquid that comes through filter paper
What is crystalisation used for
To seperate a solute from a solution
Describe how to carry out crystalisation
- Solution is heated in evaporating basin to boil off water, until an almost saturated solution is formed
- Bunsen is turned off and crystals allowed to form as more water evaporates and solution forms
- Crystals removed by filtration
Describe how to carry out crystalisation
- Solution is heated in evaporating basin to boil off water, until an almost saturated solution is formed
- Bunsen is turned off and crystals allowed to form as more water evaporates and solution forms
- Crystals removed by filtration
What is simple distillation used for
To seperate pure water from a solution
Describe how to carry out simple distillation
- Water from solution boils and is condensed back into liquid by condenser
What is fractional distillation used for
Seperate ethanol from a mixture of ethanol and water
How to carry out fractional distillation
- Control heating temperature to ensure water condenses in column and trickles back into flask
- Only ethanol with lower boiling point (than water) remains as vapour at top of fractionating column, and into condensor
Where to measure ink from a chromatgram
Centre of the spot
How to calculate Rf
Distance oved by spot (from pencil line) / Distance moved by solvent (from pencil line)
Purpose of chromatography
To seperate inks from dyes
