Everyday Phenomena and Quick Facts

Why this matters for CAPF

This is the consolidation and revision sheet for the General Science module. It gathers the high-frequency "appreciation of everyday phenomena" facts that the CAPF clause explicitly asks for: why the sky is blue, why a star twinkles, the instrument-to-use list, the SI base units, and the scientist-to-discovery list. The CAPF syllabus uses the exact words "comprehension and appreciation of scientific phenomena of everyday observation", so this material is asked directly. Use this note for last-week revision after the topic notes; everything here is at the recognition level and pairs with the deeper treatment in physics everyday, chemistry everyday and the biology notes.

Everyday phenomena and their reasons

Instruments and their uses

SI base units

Common derived units

Scientists and their discoveries

Branches of science (the "ology" list)

High-frequency miscellaneous facts

• The most abundant gas in air is nitrogen (about 78 percent); oxygen is about 21 percent; argon and carbon dioxide make up most of the rest.
• The Sun's energy comes from the nuclear fusion of hydrogen into helium.
• Diamond is the hardest natural substance and is pure carbon.
• Mercury is the only metal that is liquid at room temperature; bromine is the only non-metal liquid at room temperature.
• LPG (cooking gas) is mainly butane and propane; an odorant (ethyl mercaptan) is added to detect leaks. CNG is mainly methane.
• Dry ice is solid carbon dioxide; it sublimes directly into gas.
• The skin makes vitamin D in sunlight.
• The pH of human blood is slightly basic (about 7.4).
• Sound cannot travel through a vacuum; light can.
• Stainless steel is an alloy of iron, chromium and nickel; brass is copper and zinc; bronze is copper and tin.
• Graphite is the non-metal that conducts electricity.
• Water has its maximum density at 4° Celsius.
• The speed of light in vacuum is about 3 × 10⁸ m/s; the speed of sound in air is about 343 m/s.

How CAPF asks it (authored practice)

Common confusion

• Twinkling stars versus steady planets: stars twinkle due to atmospheric refraction of their point-like light; planets, being nearer and disc-like, twinkle far less.
• Barometer versus manometer versus hygrometer: barometer for atmospheric pressure, manometer for gas pressure, hygrometer for humidity.
• Reflection versus refraction versus scattering: reflection bounces light, refraction bends it across a medium, scattering spreads it (blue sky).
• Liquid metal versus liquid non-metal: mercury is the only liquid metal at room temperature; bromine is the only liquid non-metal.
• SI base versus derived units: the seven base units (metre, kilogram, second, ampere, kelvin, mole, candela) are fundamental; newton, joule and watt are derived from them.
• Evaporation versus boiling: evaporation happens at the surface at any temperature; boiling happens throughout at the boiling point.

Memory hook

• SI base units: "My Kind Sister Always Keeps Money Carefully" for metre, kilogram, second, ampere, kelvin, mole, candela.
• Air composition: "Nitrogen rules at 78, Oxygen serves at 21."
• "Stars twinkle, planets steady" pairs twinkling with stars only.
• "Mercury the liquid metal, bromine the liquid non-metal" keeps the room-temperature liquids apart.

Night before

• The sky is blue and sunsets are red because of scattering; blue scatters most.
• Stars twinkle due to atmospheric refraction; a straw looks bent and a pool looks shallow due to refraction.
• We see lightning before thunder because light travels much faster than sound.
• A barometer measures pressure, a hygrometer humidity, an anemometer wind speed, a lactometer milk purity, a seismograph earthquakes.
• SI base units are metre, kilogram, second, ampere, kelvin, mole, candela.
• Nitrogen is the most abundant gas in air (about 78 percent); mercury is the only liquid metal; diamond is the hardest natural substance; the Sun runs on hydrogen fusion.

Glossary

• Scattering: the spreading of light by particles, making the sky blue (Rayleigh scattering).
• Refraction: the bending of light as it passes between media of different density.
• Dispersion: the splitting of white light into its colours, as in a rainbow.
• Total internal reflection: complete reflection of light within a denser medium, seen in a mirage.
• Latent heat: heat absorbed or released during a change of state at constant temperature.
• Buoyancy: the upward force on a body immersed in a fluid (Archimedes' principle).
• Convection: heat transfer by the bulk movement of a fluid, driving sea and land breezes.
• Barometer: an instrument that measures atmospheric pressure.
• Lactometer: an instrument that checks the purity of milk by relative density.
• Seismograph: an instrument that records earthquakes.
• SI base unit: one of the seven fundamental units of the International System.
• Derived unit: a unit built from base units, such as the newton or joule.
• Allotrope: a different physical form of the same element (diamond and graphite of carbon).
• Sublimation: the direct change of a solid into vapour, as in dry ice.

Related notes

• physics everyday (the optics, mechanics and heat behind these phenomena).
• chemistry everyday (states of matter, compounds, gases and discoverers).
• human body and systems (body-related instruments and facts).
• nutrition diseases and health (scientists who developed vaccines and antibiotics).
• information technology and computing (units and terms in computing).
• syllabus index