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Topic 2 (CHEM) - Measurements and Experimental Techniques (Impurities…
Topic 2 (CHEM) - Measurements and Experimental Techniques
Measurement
Mass
[Apparatus]
: Electronic Balance
[SI Unit]
: kilogram (kg)
[Usage]
: Usually used to measure small masses of solid chemicals
[Smallest Division]
: 0.1g or 0.01g (depending on the balance)
[Accuracy]
: 0.1g or 0.01g
[Example]
: 2.4g or 2.45g
Temperature
[Apparatus]
: Mercury in glass thermometer OR alcohol thermometer
[SI Unit]
: Kelvin (K) - but ºC is used
[Smallest Division]
: 1 ºC
[Accuracy]
: 0.5 ºC
[Example]
: 35ºC / 35.5C (NOT 35.3ºC)
Time
[Apparatus]
: Digital Stopwatch
[SI Unit]
: second (s)
[Smallest Division]
: 0.1s or 0.01s
[Accuracy]
: 0.1s or 0.01s
Volume
Beaker
[Measurement]
: Measure
rough volume
of liquid
[Smallest Division]
: 10cm3
Measuring Cylinder
[Measurement]
: Measure
variable volume
of liquid
approximately
[Smallest Division]
: 1cm3
Burette
[Measurement]
: Measure
variable volume
of liquid
accurately
[Usage]
:
Titration
for formation of salts (ACIDS) - volume of acid required = initial volume - final volume (=vol used up for neutralisation reaction)
[Smallest Division]
: 0.1cm3
[Maximum]
: 50cm3
Pipette
[Measurement]
: Measure
fixed volume
of liquid
accurately
[Usage]
:
Titration
for formation of salts (ALKALIS) - A pipette is used to place an accurate amount of alkali
into the conical flask before the titration begins.
Cannot measure ODD Volume like 26.0cm3 (can measure 25.0cm3, 20cm3, 50cm3 etc)
Experimental Techniques
Read Volume of Liquid
When water/solution is placed in a glass container, forms a curved surface called a
meniscus
Meniscus can be CONVEX or CONCAVE
To read volume, align your eyes to liquid level
Measure Volume of Gas
Gas syringe is used
There is a plunger and a barrel
Impurities
Lower the melting point
The higher the impurities, the lower the melting point
Causes melting to take place over a
range of temperatures
Higher the boiling point
The higher the impurities, the higher the boiling point
Causes boiling to take place over a
range of temperatures
