2 - Measurement and experimental techniques Flashcards
S.I unit of mass
kg
How many kg in 1 tonne (t)
1000kg
what is used to measure mass quickly and accurately, temp.
Beam/ electronic balance (2 d.p)
S.I unit for time
Seconds, minute, hour
Tool to measure time?
Stopwatch
S.I unit for temp.
K (Kelvin), Degree celsius
Tool to measure temp.
Mercury/ alcohol thermometer, data logger
S.I unit for volume and its value
Cubic cm, Cubic decimeter
1m3 = 1000dm3 1dm3 = 1000cm3
Tools to measure volume?
Measuring cylinder, burette, pipette
Measuring cylinder accuracy
Measures to the nearest 0.5 cm cube
Burette accuracy and purpose
- ACCURATELY measures liquid to nearest 0.05 cm cube
- Scale marked (graduated) in 0.1 cm cube devisions
- Used to deliver different volumes of liquid
Pipette accuracy
ACCURATELY measures out fixed volumes of liquids (25cm3)
How to read volume of liquid?
Curved surface called meniscus (read at either top or bottom of it, depending on where it curves)
How measure volume of gas?
Gas syringe
Methods for collecting gas
- Displacement of water
- Downward delivery
- Upward delivery
Describe displacement of water (in terms of when collecting gas)
- Suitable for collecting gases that are insoluble or SLIGHTLY soluble in water
e. g (for this method) Oxygen, CO2, hydrogen
[Note: acid and alkalis are soluble in water, also CO2 is a weak acid]
Describe downward delivery (in terms of when collecting gas)
- Collect gas that is soluble in water AND denser than air
e. g (for this method) chlorine, hydrogen chloride
[Note: Poisonous gas should be carried out in a fume cupboard]
Describe upward delivery (in terms of when collecting gas)
- Collect gases that are soluble in water AND lighter than air
e. g (for this method) ammonia
3 methods to dry a gas
- Concentrated sulfuric acid [H2SO4]
- Quicklime (calcium oxide) [CaO]
- Fused calcium chloride [CaCl]
Describe concentrated sulfuric gas (drying a gas)
- Can dry MOST gases
- Can’t dry alkalis/ bases like ammonia as it would react with the acid
Describe Quicklime [calcium oxide] (drying a gas)
Used to dry ammonia (look at this royal gas, has a whole method of drying to itself)
Describe fused calcium chloride (drying a gas)
- Calcium chloride is heated to remove all traces of water in a gas
(can dry most gases, except ammonia)
