Science Facts for Students (Class 6–10 Lessons)

The rules in a science book make the most sense when we see them happening in everyday life. Here are science facts for students, linked directly to the lessons of Classes 6 to 10. Each fact says which topic it belongs to, so that it also helps with exam preparation.

Physics: force, pressure and energy

Why does a sharp knife cut easily? Pressure = force ÷ area. The edge has a very small area, so the same force produces a much bigger pressure. (Force and pressure)
Why doesn't a camel sink into sand? Its broad feet spread its weight over a large area, which lowers the pressure.
Why do we lurch forward when a bus stops? The body tends to stay in motion — this is called inertia (Newton's first law).
Why does a released balloon shoot off the other way? Air rushes out backwards and the balloon moves forwards — every action has an equal and opposite reaction (Newton's third law). A rocket works on the same principle.

Chemistry: in the everyday kitchen

Why does iron rust? Iron combines with oxygen and moisture in the air to form iron oxide. Paint or grease stops rusting. (Physical and chemical changes)
Why is lemon sour? It contains citric acid; lemon juice has a pH of about 2. Soap is basic, which is why it feels slippery. (Acids, bases and salts)
Why do baking soda and vinegar fizz? Their reaction produces carbon dioxide gas.
Why does a cut apple turn brown? Enzymes in the apple react with oxygen in the air. Lemon juice slows this down.

Did you know? The "sweet at the front, bitter at the back" tongue map in old books is wrong. Taste buds on every part of the tongue can detect all the tastes.

Biology: plants and the body

Why are leaves green? Chlorophyll absorbs red and blue light and reflects green. Leaves make their food by photosynthesis: carbon dioxide + water + sunlight → glucose + oxygen. (Nutrition in plants)
Why do leaves turn yellow in autumn? Chlorophyll breaks down, and the yellow-orange pigments (carotenoids) already hidden in the leaves start to show.
Why do muscles cramp in a hard sprint? When oxygen runs short, muscles respire anaerobically and make lactic acid. (Life processes) The soreness felt the next day is different — it comes from tiny damage to the muscle fibres.
Why do plants bend towards the sun? A hormone called auxin makes the shaded side grow more — this is called phototropism. (Control and coordination)

The Earth and light

Question	Answer	Lesson
Why do stars twinkle?	Their light is bent (refracted) again and again as it passes through layers of the atmosphere	Light / the human eye
Why do we see the Sun before it rises?	About 2 minutes early, because of atmospheric refraction	Light
Why does a tsunami follow an earthquake?	The sea floor shifts and sets off huge waves	Natural disasters

Read the full science of the sky's colours in Why is the sky blue. To learn chemical equations, see Chemical reactions: balancing equations.

Key points

Pressure = force ÷ area, which is why a sharp knife cuts well.
Rust is the reaction of iron with oxygen and moisture.
Lemon juice is acidic (pH about 2) and soap is basic.
In photosynthesis, leaves make food using sunlight.
The "tongue taste map" is a myth.

Frequently asked questions

What is the best way to remember science?

Find an everyday example for every rule and try small experiments at home (with an adult watching).

Are these facts asked in board exams?

Most of these topics are in the NCERT lessons for Classes 6–10, so questions based on them can come up.

Practise: Science questions · Read more: 15 amazing science facts · Science.

Science facts for students, from the Class 6–10 syllabus