PPSC Everyday Science MCQs

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.

Temporary hardness is caused mainly by bicarbonates.
Boiling converts them into insoluble precipitates.

Alloys combine metals with other elements.
They are designed for strength, corrosion resistance, or other useful properties.

Brass contains mainly copper and zinc.
It is used in fittings, instruments, and decorative items.

Bronze is primarily copper alloyed with tin.
It is harder than pure copper.

Steel contains iron with a controlled amount of carbon.
Other alloying elements can modify its properties.

Chromium in stainless steel creates a thin passive oxide film.
This layer limits further corrosion.

Copper conducts electricity well and can be drawn into wires.
It is also relatively resistant to corrosion.

Aluminium has a low density and good corrosion resistance.
Its alloys are widely used in aircraft.

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

Rusting is an oxidation process requiring oxygen and moisture.
It weakens exposed iron over time.