Everyday Science Questions for RRB GROUP D

Kitchen and Food Science

Many exam questions come from cooking and food preservation. Pressure cookers cook food faster because increased pressure raises the boiling point of water above 100 degrees Celsius, so food cooks at higher temperature. Baking soda (sodium bicarbonate) releases carbon dioxide when heated, making dough rise. Salt is added to ice to lower its melting point — this is called freezing point depression.

• Pressure cooker raises boiling point — food cooks faster
• Baking soda is NaHCO3 — releases CO2 — makes bread/cake soft
• Vinegar is dilute acetic acid — used as preservative
• Refrigerator works on evaporation of coolant absorbing heat
• Milk turns sour due to lactic acid produced by bacteria
• Iodised salt prevents goitre — iodine deficiency disease

Light and Vision in Daily Life

Light travels in straight lines and bends (refracts) when it moves from one medium to another. This is why a spoon in a glass of water looks bent. Mirages on hot roads happen because hot air near ground refracts light upward — you see a fake image of sky on the road. Rainbow forms due to dispersion of sunlight through water droplets — VIBGYOR order from top to bottom.

• Spoon in water looks bent — refraction of light
• Mirage on roads — total internal reflection in hot air
• Rainbow — dispersion of white light into 7 colours
• VIBGYOR: Violet Indigo Blue Green Yellow Orange Red
• Blue sky — scattering of light, shorter wavelengths scatter more
• Red sunset — longer wavelengths (red) travel through more atmosphere at sunset

Sound in Everyday Life

Sound needs a medium to travel — it cannot travel in vacuum. This is why there is no sound in space. Sound travels fastest in solids, then liquids, then gases. Echo is the reflection of sound from a hard surface. You need a minimum distance of about 17 metres between you and the wall to hear a clear echo. Bats use ultrasound (above 20000 Hz) for navigation — called echolocation.

• Sound cannot travel in vacuum — needs medium
• Speed: solid > liquid > gas
• Echo needs at least 17 metres distance
• Ultrasound: above 20000 Hz — used by bats and in medical scans
• Infrasound: below 20 Hz — elephants and whales use it
• Loudness measured in decibels (dB)

Electricity and Magnetism at Home

Electric fuse is a safety device — it melts and breaks the circuit when too much current flows, protecting appliances. MCB (Miniature Circuit Breaker) does the same thing but can be reset. Earthing protects humans from electric shock by providing a safe path for stray current to go into the ground. Electric bulbs glow because the tungsten filament resists current and heats up to emit light.

• Fuse wire has low melting point — breaks on excess current
• MCB is a modern replacement for fuse — reusable
• Earthing — safety wire connected to ground
• Tungsten filament in bulb — very high melting point (3422 degrees Celsius)
• CFL and LED bulbs save electricity compared to incandescent bulbs
• Magnets attract iron, nickel, cobalt — not copper or aluminium

Common Substances and Their Science

Many questions ask about properties of everyday chemicals and materials. Soap works because one end of soap molecule attracts water and the other attracts oil — so it removes oil from skin. Hard water does not lather well with soap because of calcium and magnesium salts. Rust forms when iron reacts with oxygen and water — it is iron oxide. Stainless steel does not rust because chromium forms a protective layer.

• Soap removes oil — one end hydrophilic (water-loving), one end hydrophobic (oil-loving)
• Hard water has calcium and magnesium salts — reduces soap lather
• Rust is hydrated iron oxide Fe2O3.nH2O
• Stainless steel contains chromium — prevents rusting
• LPG is mainly butane and propane — heavier than air, sinks on leaking
• CNG is mainly methane — lighter than air, safer than LPG

Human Body and Health Science

Questions about vitamins, deficiency diseases, and body functions appear frequently. Blood group system and Rh factor basics are also tested. Normal human body temperature is 37 degrees Celsius or 98.6 degrees Fahrenheit. The heart pumps blood — a healthy adult heart beats about 72 times per minute. Hemoglobin in blood carries oxygen — iron deficiency causes anaemia.

• Normal body temperature: 37 degrees C or 98.6 degrees F
• Normal heart rate: 72 beats per minute
• Vitamin C deficiency: Scurvy — bleeding gums
• Vitamin D deficiency: Rickets in children, Osteomalacia in adults
• Vitamin A deficiency: Night blindness
• Iron deficiency: Anaemia — less haemoglobin in blood

• Confusing baking soda (NaHCO3) with baking powder — baking powder contains baking soda plus an acid like tartaric acid. Exam often asks which one releases CO2.
• Thinking sound travels fastest in air — it actually travels fastest in solids. Many aspirants reverse the order.
• Mixing up LPG and CNG properties — LPG is heavier than air and sinks, CNG is lighter and rises. This matters in safety questions.
• Confusing Vitamin D (rickets) with Vitamin C (scurvy) deficiency diseases — use a mnemonic to separate them.
• Saying mirage happens due to reflection — it is actually due to total internal reflection in hot air layers, which is a form of refraction at extreme angles.

• VIBGYOR — Violet Indigo Blue Green Yellow Orange Red for rainbow colours from top to bottom. Remember as Very Intelligent Boys Generally Yield Outstanding Results.
• SAD vitamins need fat to absorb: A, D, E, K are fat-soluble. B and C are water-soluble. For deficiency diseases: A = bAndness (night blindness), D = Deformed bones (rickets), C = Cut gums (scurvy).
• For sound speed: SAL — Solid is fastest, Air (gas) is slowest, Liquid is in the middle. Think of shouting through a wall versus air.
• LPG sinks, CNG floats — think L for Low (LPG sinks to floor), C for Ceiling (CNG rises up).

• RRB Group D asks mostly one-liner factual questions from everyday science — no long calculations. A question like which gas is used in LPG or why pressure cooker cooks fast are very common.
• Deficiency diseases and vitamins appear almost every year. Memorise the vitamin-disease pair table — at least 1 question guaranteed.
• Questions on safety devices like fuse, MCB, and earthing appear regularly in the electricity section. Know their function and difference.
• Do not skip light and sound topics — at least one question on refraction (bent spoon or mirage) or echo appears in most papers.
• Everyday chemistry questions like why soap removes dirt, why stainless steel does not rust, or what LPG contains are easy marks — spend 2 minutes revising these before the exam.