- Analogue stopwatch : that consists of a knob, secondary dial and a main dial.
- Digital stopwatch : This is a much more accurate and rather a required stopwatch in the modern experiments due to more precision in it.
The SI (System International) Unit is cubic meters m3 that is equal to 1000 litres.
|Beaker||Usually used in approximation of liquid, Approximately 100 cm3|
|Measuring Cylinder||Although better than beaker but has its precision limited to 1 cm3|
|Burette||Helps to measure the liquid almost to 0.1 cm3 with 0.1 cm3 divisions present on the instrument.|
|Pipette||This is specifically used to fill fixed volumes e.g. 25 cm3, is usually accompanied with a rubber pipette filler for safety purposes.|
Collecting and Measuring Volume of Gases
Gases solubility and density compared to air
Density of gas = 30 (air density)
- NH3 SOLUBLE BASIC Lighter
- CL2 SOLUBLE ACIDIC Denser
- Hcl SLIGHTLY SOLUBLE ACIDIC Denser
- S02 SLIGHTLY SOLUBLE ACIDIC Denser
- O2 SOLUBLE NEUTRAL Slightly Denser
- CO2 INSOLUBLE ACIDIC Denser
- H2 INSOLUBLE NEUTRAL Lighter
Gases insoluble in water are collected through displacement of water.
Gases lighter than air are collected through Upward Delivery.
Gases denser / heavier than air are collected through upward delivery.
It is required to dry a gas when it is collected through a solvent. The common drying agents are fused calcium chloride, calcium oxide and concentrated sulfuric acid. The tube of the moist gas should be immersed in the drying agent and the second tube must be out of it.
Criteria of purity
A substance is said to be pure when it is made up of only one substance. This substance should not be mixed neither combined with other.
Methods of purification
To figure out the impurities present in a substances, there are different methods that are given below:
Fixed Melting / Boiling Point
- Pure solids have fixed melting points, with impurities a depression in melting point is seen.
- Pure liquids have fixed boiling points, with impurities an elevation in boiling point is seen.
Definition: A technique / process where a solvent is used to separate a mixture into its components.
Chromatography helps us in separating a sample’s components and identify the number of components in the sample and whether the sample is pure.
It is a ratio that means it does not have any units.
Distance travelled by the substance / Distance travelled by the substance
Separating a Solid from a Liquid
This can be called as the simplest technique of separating a substance where water is just poured away.
A process where small solid particles are separated from a solvent. The filter papers sieves the solid particles that is called as residue and the water that is passed down is called filtrate.
This separation technique is used when a soluble substance is used to separate from water. To separate it is heated, water is evaporated, This technique is also known as Evaporation to dryness. The end result is the solid product; however, substances decompose in this process as well.
Substances that are attracted with magnets can be separated from those that are not with help of a magnet only.
Solids sublime to gases. Substances that sublime can be separated from those that cannot.
Process where a liquid is boiled and vapor is condensed back. The two liquids have different boiling points where one boils off first than the other.
When two liquids are miscible , fractional distillation is the most feasible way to do that. The process is almost same as simple distillation. The process can separate more than two different solvents.