Q.1 Why do we add salt to ice when making homemade ice cream?
To make ice melt slower
To raise the melting point of ice
To lower the melting point of ice
To sweeten the mixture
Explanation - Salt lowers the melting point of ice, causing it to melt at lower temperatures, which absorbs heat and helps freeze the ice cream mixture faster.
Correct answer is: To lower the melting point of ice
Q.2 Why are cooking pans often made with metal but have plastic or wooden handles?
Metals are poor conductors of heat
Plastic and wood are poor conductors of heat
Plastic makes the pan stronger
Wood makes the food taste better
Explanation - Metals conduct heat well, so they are used for cooking. Handles are made of poor conductors like plastic or wood to prevent burns.
Correct answer is: Plastic and wood are poor conductors of heat
Q.3 Why do pressure cookers cook food faster?
They use more heat
They increase the boiling point of water
They reduce the boiling point of water
They use electricity instead of gas
Explanation - Pressure cookers trap steam, increasing pressure, which raises the boiling point of water and cooks food faster.
Correct answer is: They increase the boiling point of water
Q.4 Why do we add iodine to table salt?
To make it taste better
To prevent goiter
To prevent rusting
To make it whiter
Explanation - Iodine is added to salt to prevent iodine deficiency, which can cause goiter (swelling of the thyroid gland).
Correct answer is: To prevent goiter
Q.5 Why do athletes drink sports drinks after exercise?
To replace lost vitamins
To replace lost electrolytes
To reduce fatigue instantly
To help them sleep
Explanation - Sports drinks replenish electrolytes like sodium and potassium lost through sweat, helping maintain body function and hydration.
Correct answer is: To replace lost electrolytes
Q.6 Why do refrigerators have freezers at the top in older designs?
Because cold air rises
Because cold air sinks
To save electricity
For easier access
Explanation - Cold air sinks downward, so placing the freezer at the top allows cold air to circulate and keep the whole refrigerator cool.
Correct answer is: Because cold air sinks
Q.7 Why do we see lightning before hearing thunder?
Light travels faster than sound
Sound travels faster than light
Lightning is brighter than thunder
Thunder is delayed due to clouds
Explanation - Light travels much faster than sound, so we see lightning almost instantly, but sound (thunder) reaches us later.
Correct answer is: Light travels faster than sound
Q.8 Why are microwaves used for cooking food?
They heat air in the oven
They directly heat food molecules
They reflect off metal surfaces
They cool the food first
Explanation - Microwaves excite water molecules in food, producing heat directly inside the food and cooking it quickly.
Correct answer is: They directly heat food molecules
Q.9 Why do we feel cold after sweating?
Because sweat absorbs heat from our body when it evaporates
Because sweat is cold
Because skin releases cold air
Because sweat contains ice
Explanation - Evaporation of sweat requires heat, which is taken from our body, making us feel cool.
Correct answer is: Because sweat absorbs heat from our body when it evaporates
Q.10 Why is stainless steel used for making surgical instruments?
It is cheap
It is rust-resistant and strong
It is flexible
It is magnetic
Explanation - Stainless steel resists rust and maintains strength, making it suitable for surgical instruments.
Correct answer is: It is rust-resistant and strong
Q.11 Why does food cook faster in a microwave than in a conventional oven?
Microwave energy penetrates food directly
Microwave ovens are hotter
Microwaves use higher voltage
Conventional ovens heat food from the outside only
Explanation - Microwaves heat food molecules directly, while conventional ovens transfer heat slowly from the outside to inside.
Correct answer is: Microwave energy penetrates food directly
Q.12 Why is toothpaste often slightly basic?
To taste sweet
To neutralize acids in the mouth
To kill all bacteria instantly
To whiten teeth directly
Explanation - Toothpaste is slightly basic to neutralize acids produced by bacteria, protecting tooth enamel from decay.
Correct answer is: To neutralize acids in the mouth
Q.13 Why are thermal flasks used to keep liquids hot or cold?
They are made of metal
They prevent heat transfer
They increase heat energy
They absorb heat
Explanation - Thermal flasks use vacuum insulation and reflective surfaces to reduce heat transfer, keeping liquids hot or cold longer.
Correct answer is: They prevent heat transfer
Q.14 Why is copper used in electrical wiring?
It is cheap
It is a good conductor of electricity
It resists electricity
It is very heavy
Explanation - Copper is an excellent conductor and relatively inexpensive, making it ideal for electrical wiring.
Correct answer is: It is a good conductor of electricity
Q.15 Why do we apply ointment on burns?
To make the skin shiny
To reduce infection and aid healing
To remove scars instantly
To cool the skin by evaporation
Explanation - Ointments contain antiseptics and healing agents that prevent infection and promote skin recovery.
Correct answer is: To reduce infection and aid healing
Q.16 Why do astronauts wear space suits?
For fashion
To protect from cold, lack of oxygen, and radiation
To move easily
To look like robots
Explanation - Space suits provide oxygen, regulate temperature, and protect astronauts from harmful radiation in space.
Correct answer is: To protect from cold, lack of oxygen, and radiation
Q.17 Why is glass used in windows?
It is transparent and lets light in
It is a good insulator of heat
It is stronger than steel
It changes color with sunlight
Explanation - Glass is transparent, allowing light to enter while providing protection from weather.
Correct answer is: It is transparent and lets light in
Q.18 Why do car tires have grooves?
To make them look stylish
To improve grip and prevent skidding
To make cars faster
To reduce weight
Explanation - Grooves allow water to escape from under tires, improving grip on wet surfaces and preventing skidding.
Correct answer is: To improve grip and prevent skidding
Q.19 Why do we wear woolen clothes in winter?
They generate heat
They trap air and reduce heat loss
They are heavy
They reflect sunlight
Explanation - Woolen clothes trap air, a poor conductor of heat, keeping the body warm in winter.
Correct answer is: They trap air and reduce heat loss
Q.20 Why does water appear shallower than it really is?
Due to reflection
Due to refraction
Due to scattering
Due to absorption
Explanation - Light bends when passing from water to air, making the bottom of a pool appear shallower.
Correct answer is: Due to refraction
Q.21 Why is chlorine used in swimming pools?
To keep the water cool
To kill harmful microorganisms
To make water blue
To reduce evaporation
Explanation - Chlorine disinfects swimming pool water by killing harmful bacteria and germs.
Correct answer is: To kill harmful microorganisms
Q.22 Why does a black car get hotter in the sun than a white car?
Because black absorbs more heat
Because white reflects heat
Because black is heavier
Because white is lighter
Explanation - Black surfaces absorb more heat from sunlight, while white surfaces reflect it.
Correct answer is: Because black absorbs more heat
Q.23 Why is aluminum foil used for wrapping food?
It reflects heat and prevents moisture loss
It makes food tastier
It is cheaper than plastic
It prevents bacteria growth forever
Explanation - Aluminum foil reflects heat and prevents loss of moisture, keeping food warm and fresh longer.
Correct answer is: It reflects heat and prevents moisture loss
Q.24 Why do glass bottles sometimes crack when filled with hot water?
Because glass is a good conductor
Because of uneven expansion due to heat
Because glass absorbs water
Because glass becomes weak when hot
Explanation - The inner surface of the glass expands faster than the outer surface, causing stress and cracks.
Correct answer is: Because of uneven expansion due to heat
Q.25 Why do we feel lightheaded at high altitudes?
Less oxygen is available
There is more oxygen
The air is heavier
Gravity is weaker
Explanation - At higher altitudes, air pressure and oxygen levels are lower, making it harder to breathe and causing lightheadedness.
Correct answer is: Less oxygen is available