Measurement of Time

Apparatus : stopwatch or stopclock

Unit : seconds (s) minutes (min) or hours (h)

Measurement of Temperature

• Apparatus : thermometer• Unit : degree Celsius (°C)

Kelvin (K)

thermometer

Measurement of Mass Apparatus : electronic balance

Unit : gram (g)kilogram (kg)

mass of the chemical can be

read off the balance displayelectronic

‘top pan’ balance

Measurement of Volume

Apparatus : burette for measuring

accurately the volume of a liquid (0 to 50.0cm3)

Accuracy : to nearest 0.1cm3

Volume of Liquids :

accurate volume from 0 to 50 cm3 can be measured by reading the differences of the levels before and after the liquid is released; commonly used in titrations

0 ml mark

50 ml mark

Measurement of Volume

0 ml mark

50 ml markBurette reading : 3.4cm3

Measurement of Volume

Initial : 0.8cm3

Final : 26.5cm3

Initial reading Final reading

Volume of liquid added =

(26.5 - 0.8)cm3

= 25.7 cm3

Measurement of Volume

Apparatus :pipette for measuring

accurately a fixed volume of liquid (20.0cm3 or 25.0cm3

usually) Accuracy : to nearest

0.1cm3

Volume of Liquids :

pipette

accurate set volume of exactly 20, 25 or 50 cm3 of liquid (to the nearest 0.1cm3) can be drawn to a

mark, using a pipette filler

Measurement of VolumePipette

pipette

accurate set volume of exactly 20, 25 or 50 cm3 of liquid (to the nearest 0.1cm3) can be drawn to a

mark, using a pipette filler

Measurement of Volume

Apparatus :measuring cylinder Accuracy : to nearest 1cm3

Volume of Liquids :

measuring cylinder

accurate volume to the nearest cm3

of liquid can be measured

Measurement of Volume

Measuring cylinder

Correct reading: 46 cm3 Correct reading: 47 cm3

Measurement of Volume

Apparatus :beaker For approximate volume

of liquids

Volume of Liquids :

Measurement of Volume

Apparatus : gas syringeVolume of Gases :

gas syringe

accurate volume of gas can be manually read on the graduated scale, or

automatically recorded using data logging

rubber bung

hydrochloric acid + lumps

of calcium carbonate

conical flask

Measurement of Volume

Units :

cubic centimetres (cm3), decimetres (dm3),litres(l) and millilitres(ml)

Some conversions:

1 l = 1000 ml

1 l = 1 dm3 = 1000 cm3

1 ml = 1cm3

Experimental Set-upTo dry a gas :

Use of concentrated sulfuric acid, quick lime (calcium oxide) or fused calcium chloride.

Experimental Set-upCollecting Gases in the laboratory :

Gases may be collected (1) using a gas syringe OR

(2) based on the physical properties of the gas: The solubility of the gas in water

The density of the gas compared to the density of air

3 Methods of collecting gases:

Displacement of water

Displacement of air – downward displacement

Displacement of air – upward displacement

Collecting gasesDisplacement of water :

Used on gases that are insoluble or slight soluble in water, e.g. hydrogen, oxygen, carbon dioxide, etc.

Delivery tubeGas

GasGas jar

Collecting gasesDisplacement of air - downward delivery

For fairly soluble or very soluble gases in water that are heavier or denser than air.

E.g. chlorine, hydrogen chloride

Delivery tube

Gas jar

Gas

Gas

Collecting gasesDisplacement of air - upward delivery

For fairly soluble or very soluble gases in water that are lighter or less dense than air.

E.g. ammonia

Delivery tubeGas jar

Gas

Gas