PPSC Everyday Science Past Paper 2025 Solved MCQs with Answers
Solved Everyday Science MCQs from the PPSC 2025 past paper, each with the correct answer and a clear explanation. Ideal practice for PPSC, FPSC, NTS, CSS and PMS. All questions are extracted from the actual 2025 paper and verified before publication.
The Mohorovicic discontinuity (Moho) is the boundary between:
The Mohorovicic discontinuity, found by Andrija Mohorovicic in 1909, marks the boundary between the crust and the mantle, where seismic waves suddenly speed up.
The mantle is composed mainly of:
The mantle is made chiefly of ferro-magnesium silicates, iron and magnesium rich rock such as peridotite.
The asthenosphere is a:
The asthenosphere is a weak, partly molten zone of the upper mantle on which the rigid plates of the lithosphere slide.
The outer core is composed of:
The outer core is a nickel-iron alloy in the liquid state, which is why shear waves cannot pass through it.
What controls Earth's magnetic field?
Convection currents in the liquid outer core generate the earth's magnetic field, by the dynamo effect.
The inner core is composed almost entirely of:
The inner core is almost entirely iron, kept solid despite its heat by the immense pressure at the centre of the earth.
What is the lithosphere?
The lithosphere is the rigid outer shell, made of the crust together with the solid uppermost part of the mantle.
An atom consists of:
An atom is made of electrons, protons and neutrons. Only ordinary hydrogen lacks a neutron.
The nucleus of an atom contains:
The nucleus holds the protons and neutrons. The electrons orbit outside it.
Electrons carry which charge?
Electrons carry a negative charge.
Neutrons carry which charge?
Neutrons carry no charge, which is what makes them useful for penetrating a nucleus.
In a neutral atom, the number of electrons equals the number of:
A neutral atom has as many electrons as protons, so the charges cancel.
Atoms of the same element with different numbers of neutrons are called:
Atoms of one element with different numbers of neutrons are isotopes. Isobars have the same mass number but different elements.
Who proposed that atom is the smallest indivisible particle?
John Dalton proposed in 1803 that the atom is the smallest indivisible particle of matter.
The nucleus of the atom was discovered by:
Ernest Rutherford discovered the nucleus in 1911, from his gold foil experiment.
How many elements exist in total?
The periodic table now holds 118 confirmed elements.
How many different kinds of atoms exist in nature?
About 92 elements occur naturally on earth. The rest have been made artificially.
Atomic number of an element is equal to the number of:
The atomic number equals the number of protons, and it is what fixes the identity of the element.
Radioactive elements have a nucleus that is:
A radioactive element has an unstable nucleus, which decays and emits radiation until it reaches a stable form.
Half-life is the time required for ___ of nuclei to decay:
The half-life is the time in which half the nuclei in a sample decay.
Half-life of Carbon-14 is:
Carbon-14 has a half-life of 5730 years, which is what makes it useful for dating organic remains.
Radioactive decay of uranium ultimately produces:
The uranium decay series ends at a stable isotope of lead.
Which of the following is NOT radioactive?
Zirconium is not radioactive. Uranium, radium and plutonium all are.
Alpha particles carry charge:
An alpha particle is a helium nucleus, two protons and two neutrons, so it carries a charge of +2.
Gamma rays are:
Gamma rays are electromagnetic radiation, not particles. Alpha and beta emissions are particles.
Which radiation is the most penetrating?
Gamma radiation is the most penetrating, needing thick lead or concrete to stop it.
Which radiation is stopped by a sheet of paper?
Alpha particles are stopped by a sheet of paper or a few centimetres of air, because of their large mass and charge.
Energy of a gamma photon is approximately:
A gamma photon typically carries an energy of the order of a few MeV, commonly quoted as about 2 MeV.
Gamma rays travel at:
Gamma rays are electromagnetic waves and so travel at the speed of light.
Nuclear fission is the:
Fission is the splitting of a heavy nucleus into lighter ones. Fusion is the joining of light nuclei.
Nuclear fission is triggered by:
Fission is triggered by a neutron striking the nucleus, and the neutrons released then continue the chain.
The fissile isotope of uranium is:
Uranium-235 is the fissile isotope used in reactors and weapons.
The most common isotope of uranium in nature is:
Uranium-238 makes up over 99 per cent of natural uranium. U-235 is only about 0.7 per cent.
In a nuclear reactor, the chain reaction is:
In a reactor the chain reaction is controlled, by rods that absorb surplus neutrons. In a bomb it is left uncontrolled.
Atomic bomb is based on the principle of:
The atomic bomb works by nuclear fission. The hydrogen bomb uses fusion.
Coolant used in nuclear reactors is:
Liquid sodium is used as a coolant in fast breeder reactors, since it carries heat well and does not slow the neutrons.
Moderator/reflector in many reactors is:
Graphite is used as a moderator and reflector, slowing neutrons so that they are more readily captured.
Highly enriched isotopes are produced by:
Uranium is enriched in ultracentrifuges, which separate the slightly lighter U-235 from U-238 by spinning the gas at high speed.
In an atomic explosion, energy comes from:
The energy of a nuclear explosion comes from the conversion of mass into energy, in accordance with E equals mc squared.
Wavelength of visible light ranges:
Visible light runs from about 3900 to 7600 angstroms, that is violet to red.
VIBGYOR / ROYGBIV represents:
VIBGYOR names the seven colours of the rainbow, from violet through to red.
In the EM spectrum, which has the shortest wavelength?
Gamma rays have the shortest wavelength and the highest energy in the electromagnetic spectrum.
Which rays help read faded old writings?
Infrared rays reveal faded or erased writing, since old inks reflect and absorb infrared differently from the paper.
The primary rainbow has an angular radius of about:
The primary rainbow forms an arc of about 40 to 42 degrees from the antisolar point.
Polythene is made by polymerization of:
Polythene is made by the polymerisation of ethylene.
Conversion of water to steam is a:
Water turning to steam is a physical change. No new substance forms, and cooling reverses it.
Condensation is the change of state from:
Condensation is the change from gas to liquid.
Rusting of iron is a type of:
Rusting is oxidation, iron combining with oxygen and water to form hydrated iron oxide.
Cooking oils are converted to vegetable ghee by:
Vegetable ghee is made by hydrogenation, adding hydrogen across the double bonds of the oil to harden it.
About the PPSC Everyday Science Past Paper 2025
Every MCQ above is taken from the Punjab Public Service Commission (PPSC) Everyday Science papers held in 2025, with the correct answer and a written explanation for each. Past-paper practice is the most dependable way to prepare for PPSC, FPSC, NTS, CSS and PMS, because these papers repeat their themes, and often the questions themselves, from one year to the next.
Questions were checked against reliable sources before publication. Where a circulating source sheet carried a factual or wording error, we corrected it rather than reproducing the mistake. For chapter-wise preparation, work through our Everyday Science MCQs hub, which also lists every other year’s paper. Further reading: Pakistan Movement and the PPSC official website.
How to Use This Paper
Attempt the full quiz before looking at any answer, then read the explanation for every question you got wrong, including those you guessed correctly. A past paper is only useful if you close the gaps it exposes. Pro members can download the complete paper as a PDF with all answers and explanations for offline revision.