Everyday Science: 20 Facts Candidates Commonly Mix Up

Everyday Science questions are usually short and factual, which makes them quick marks. But the same few pairs of facts trip people up again and again, because each pair sounds similar. Here they are, grouped so you can learn them side by side.

Body and health

1. Largest organ vs largest gland. The skin is the largest organ; the liver is the largest internal organ and largest gland.
2. Longest bone vs smallest bone. The femur (thigh) is the longest; the stapes (in the ear) is the smallest.
3. Universal donor vs universal recipient. O negative red cells can be given to anyone in an emergency; AB positive people can receive red cells from any group.
4. Red cells vs platelets. Red blood cells carry oxygen; platelets help blood clot.
5. Vitamin C vs vitamin D deficiency. Lack of C causes scurvy (bleeding gums); lack of D causes rickets (soft bones).
6. Vitamin A vs vitamin K. A is needed for vision in dim light (night blindness when lacking); K is needed for blood clotting.
7. Malaria vs dengue. Malaria is caused by a Plasmodium parasite spread by Anopheles mosquitoes; dengue is caused by a virus spread mainly by Aedes mosquitoes.

Physics

8. Joule vs watt. A joule measures energy or work; a watt measures power, the rate of using energy (one joule per second).
9. Barometer vs hygrometer. A barometer measures air pressure; a hygrometer measures humidity.
10. Ammeter vs voltmeter. An ammeter measures current (connected in series); a voltmeter measures voltage (connected in parallel).
11. Speed of light vs speed of sound. Light: about 3 × 10⁸ m/s. Sound in air: about 343 m/s. Sound cannot travel through a vacuum at all.
12. Convex vs concave mirror. Vehicles use convex mirrors for a wider view; concave mirrors are used in torches and shaving mirrors.
13. Light-year. A unit of distance, not time. Exam options often include “time” to catch you.

Chemistry

14. Baking soda vs washing soda. Baking soda is sodium bicarbonate (NaHCO₃); washing soda is sodium carbonate (Na₂CO₃·10H₂O).
15. Most abundant element vs most abundant metal in the Earth’s crust. Oxygen is the most abundant element; aluminium is the most abundant metal.
16. Helium vs hydrogen in balloons. Hydrogen is lighter but flammable; helium is used because it is non-flammable.
17. CNG vs LPG. CNG is mostly methane; LPG is mainly propane and butane.

Space

18. Hottest planet vs closest to the Sun. Mercury is closest, but Venus is hottest because its thick atmosphere traps heat.
19. Solar vs lunar eclipse. In a solar eclipse the Moon blocks the Sun; in a lunar eclipse the Earth’s shadow falls on the Moon.
20. First in space vs first on the Moon. Yuri Gagarin (1961) was the first human in space; Neil Armstrong (1969) was the first to walk on the Moon.

How to use this list

Read one section a day and, for each pair, say aloud why the two facts differ. The reason is what makes it stick. Then test yourself on the matching topics: Human Body, Physics Units, Chemistry and Space.