For Class 8, 9 & 10
Foundation - a strong base in Physics, Chemistry, Maths & Biology
Concept-first questions with clear model answers across all four subjects, aligned to NCERT. Start early, build the habit, and walk into your board exams, NEET and JEE already ahead.
Showing 6 questions in Chemistry for Class 8. Tap a card to reveal the answer.
ChemistryMaterials: Metals and Non-MetalseasyState two physical properties that distinguish metals from non-metals.
Reveal answer ↓
What it is
Metals are shiny, bendable conductors of heat and electricity; non-metals are dull, brittle insulators.
Answer
Metals are generally lustrous (shiny), malleable and ductile, good conductors of heat and electricity, and sonorous. Non-metals are usually dull, brittle (break easily) and poor conductors of heat and electricity. For example, iron is a shiny conductor while sulphur is a dull, brittle insulator.
- •Metals: lustrous, malleable, ductile, good conductors, sonorous
- •Non-metals: dull, brittle, poor conductors
- •Example: iron (metal) vs sulphur (non-metal)
Why learn this
It's why wires are made of copper (a metal) and a matchstick tip uses sulphur (a non-metal).
💡 Memory trick
Metals join the 'MSC' club: Malleable, Shiny, Conductors.
ChemistryCombustion and FlamemediumWhat three conditions are necessary for combustion to take place?
Reveal answer ↓
What it is
Burning needs three partners together: fuel, oxygen and enough heat.
Answer
For combustion, three things must be present together: a combustible substance (fuel), a supporter of combustion (usually oxygen from air) and heat to raise the fuel to its ignition temperature. If any one is removed, burning stops - which is why covering a fire with a blanket (cutting off oxygen) or water (cooling below the ignition temperature) puts it out.
- •Fuel (combustible substance)
- •Oxygen (supporter of combustion)
- •Heat to reach ignition temperature
- •Remove any one -> burning stops
Why learn this
It's exactly how firefighters put out fires - remove any one partner and the fire dies.
💡 Memory trick
Fire Triangle: Fuel + Oxygen + Heat. Break one side, break the fire.
ChemistryCoal and PetroleumeasyWhy are coal and petroleum called fossil fuels, and why should we use them carefully?
Reveal answer ↓
What it is
Coal and petroleum are fuels formed from ancient buried life over millions of years.
Answer
Coal and petroleum are called fossil fuels because they were formed from the dead remains of prehistoric plants and animals buried under the earth for millions of years under high heat and pressure. They are exhaustible natural resources - they take millions of years to form but are being used up fast - so they must be conserved and used carefully.
- •Formed from prehistoric dead organisms
- •Take millions of years to form
- •Exhaustible (non-renewable)
- •Must be conserved
Why learn this
They are running out and cause pollution - the reason the world is shifting to solar power and EVs.
💡 Memory trick
Fossil = from long-dead life; Exhaustible = it will Exit (run out).
ChemistrySynthetic Fibres and PlasticsmediumWhy is the disposal of plastic a serious environmental problem?
Reveal answer ↓
What it is
Most plastics do not rot (they are non-biodegradable), so they pile up for centuries.
Answer
Most plastics are non-biodegradable, which means micro-organisms cannot break them down, so they stay in the environment for hundreds of years. Burning plastic releases harmful gases, and discarded plastic chokes drains, harms animals that swallow it and pollutes soil and water. The best approach is to reduce, reuse and recycle plastic.
- •Plastics are non-biodegradable
- •Persist for hundreds of years
- •Burning releases toxic gases
- •Solution: reduce, reuse, recycle
Why learn this
It drives ocean pollution and single-use plastic bans - real citizenship science.
💡 Memory trick
Plastic = Plenty-lasting. Fight it with the three R's: Reduce, Reuse, Recycle.
ChemistryPollution of Air and WatermediumWhat is the greenhouse effect and why is it a concern today?
Reveal answer ↓
What it is
Greenhouse gases act like a blanket that traps the Sun's heat around the Earth.
Answer
The greenhouse effect is the trapping of the Sun's heat near the Earth's surface by gases like carbon dioxide, methane and water vapour, which keeps the planet warm enough for life. It becomes a concern when human activities release extra greenhouse gases, trapping too much heat and causing global warming and climate change.
- •Gases (CO2, methane, water vapour) trap the Sun's heat
- •The natural effect keeps Earth warm enough for life
- •Excess gases -> global warming and climate change
Why learn this
It explains climate change - the biggest environmental challenge of your generation.
💡 Memory trick
Like a car in the sun: heat gets in but can't get out. Too much = overheating (warming).
ChemistryCombustion and FlamemediumWhat are the characteristics of a good fuel?
Reveal answer ↓
What it is
A good fuel gives lots of heat, is cheap, easy to store and burns cleanly.
Answer
A good fuel should have a high calorific value (release a large amount of heat per kilogram), a moderate ignition temperature, be readily available and cheap, be easy to store and transport, and burn without leaving much ash or releasing harmful smoke. For example, LPG is a good domestic fuel because it has a high calorific value and burns cleanly.
- •High calorific value (much heat per kg)
- •Moderate ignition temperature, cheap, available
- •Easy to store and transport, little ash or smoke
Why learn this
It's how we choose cooking gas, vehicle fuel and industrial fuel - and cut pollution.
💡 Memory trick
A good fuel: high Calorific value, Cheap, Clean, easy to Carry - the four C's.