U6 - Experimental techniques Flashcards
What is the instrument + SI unit used for time
Stopwatch
Seconds(s)
Def: Temperature
measure of the average kinetic energy of the particles.
How does alcohol move up thermometer
Liquid in bulb expands when heated, and moves up the capillary tube
Temp SI unit and its amount in *C
Kelvin, 273.15 *C
Def: Mass
Mass is the amount of matter in a body/object,
instrument used to measure mass and its SI unit
Balance scale
Kg
Measuring instruments of volume
Measuring
Cylinder Pipette
Burette
Unit of volume
cm3
Characteristics of pure substances
- Elements / compounds
- One kind of substance
- Constant composition
atoms for every one oxygen atom in water. - Melt and boil at specific constant temperatures
- Can only be separated by chemical reactions
Characteristics of impure substances
- Mixtures
- 2 or more substances added together with no chemical bonds between the substances
- Different substances in varying amounts
- Melt and boil over a range of temperature
- Separated by physical means
What are the methods of purification
Filtration
Crystallisation
Recrystallisation
Simple distillation
Fractional distillation
Fractional distillation in crude oil
Explain briefly Filtration
Insoluble substance separated
from a liquid
Briefly explain crystallisation
Remove a soluble solid dissolved in a liquid.
.Briefly explain recrystallisation
An impure compound is dissolved in a hot solution, then cooled allowing the substance
to crystallise
Briefly explain simple distillation
A pure liquid is obtained from a solution.
Briefly explain fractional distillation
Separates two of more liquids of which the range of boiling points between the liquids is
less than 50°C.
Briefly explain fractional distillation in crude oil
used to to refine crude oil int separate materials.
Explain what Paper chromatography is
Separates a mixture by passing it in solution or suspension through a medium in which the components move at different rates.
The least soluble substance is left behind first, while the most soluble substance is carried the furthest
What are locating agents used for
used to identify colourless substances.
How do you get Rf values
Rf values = distance travelled by the spot relative to the distance travelled by the solvent
