Pakistan MCQs

Liquefied petroleum gas is mainly propane and butane.
Pressure keeps these gases liquid in cylinders.

Coal formed from buried plant matter over geological time.
Heat and pressure changed the material into carbon-rich fuel.

Crude petroleum contains many hydrocarbon compounds.
Refining separates it into useful fractions.

Crude oil is heated and separated in a fractionating column.
Components condense at different heights according to boiling point.

Petrol is a volatile petroleum fraction used in spark-ignition engines.
It contains a blend of hydrocarbons.

Higher octane fuel resists premature ignition under compression.
This reduces knocking in suitable engines.

Cooling slows metabolism of many microorganisms.
It also slows enzyme activity and spoilage reactions.

High salt concentration lowers available water through osmosis.
Many spoilage microbes cannot grow well under these conditions.

Mercury remains liquid at typical room temperatures.
Its toxicity has reduced its use in household instruments.

Pencil cores are made mainly of graphite mixed with clay.
Graphite is a form of carbon.

Calcium and magnesium ions cause hardness.
Hard water forms scale and reduces soap lather.

Hardness ions react with soap molecules.
The insoluble products waste soap and reduce lather.