Science Quiz for Class 7

Where in the human body does the digestion of food begin?

• Stomach
• Mouth
• Small intestine
• Food pipe

Answer: Mouth. Digestion begins in the mouth. Saliva breaks down starch into sugar, which is why a piece of chapati starts to taste sweet if you chew it for a while.

Which blood vessels carry blood away from the heart to all parts of the body?

• Veins
• Capillaries
• Arteries
• Nerves

Answer: Arteries. Arteries carry blood away from the heart, and veins bring it back. The pulse you feel at your wrist is in an artery.

Normal human body temperature is about...

• 37°C
• 98°C
• 27°C
• 47°C

Answer: 37°C. Normal body temperature is about 37°C. The 98 you may remember is in Fahrenheit: 98.6°F is the same as 37°C.

A turmeric (haldi) stain on a white shirt turns red when the shirt is washed with soap. Why?

• Soap is acidic
• Water is acidic
• Soap is neutral
• Soap is basic

Answer: Soap is basic. Turmeric is a natural indicator. It stays yellow in acidic and neutral substances but turns red in a base, and soap solution is basic.

Cars and bikes use which kind of mirror as a rear-view mirror, because it shows a wider area behind?

• Plane mirror
• Concave mirror
• Convex mirror
• A glass lens

Answer: Convex mirror. A convex mirror always gives an upright, smaller image and covers a wide area. Concave mirrors are used in torches and by dentists.

You wind an insulated wire around an iron nail and pass an electric current through the wire. What happens to the nail?

• It becomes a magnet
• It starts to glow
• It melts
• It rusts at once

Answer: It becomes a magnet. A current through a coil makes it magnetic, and the iron nail inside makes the effect stronger. This is an electromagnet; switch off the current and most of the magnetism goes.

Amarbel (Cuscuta) is a yellow, wire-like plant that wraps around other plants and has no chlorophyll. How does it get its food?

• It makes food using sunlight
• It takes food from the plant it climbs
• It traps and digests insects
• It absorbs food from rotting matter

Answer: It takes food from the plant it climbs. Cuscuta is a parasite. It cannot make its own food, so it takes ready-made food from the plant it grows on, called the host.

Water escapes from leaves as vapour through tiny pores. What are these pores called?

• Root hairs
• Xylem
• Veins
• Stomata

Answer: Stomata. Stomata are tiny openings, mostly on the underside of leaves. Losing water through them is called transpiration, and it helps pull water up from the roots.

During very hard exercise, muscle cells run short of oxygen and break down glucose without it. What do they produce?

• Lactic acid
• Alcohol
• Extra oxygen
• Starch

Answer: Lactic acid. Without enough oxygen, muscle cells break glucose down only partly, into lactic acid, and get less energy. Yeast respires without oxygen too, but it makes alcohol and carbon dioxide.

A simple pendulum makes 20 complete oscillations in 32 seconds. What is its time period?

• 0.625 s
• 1.6 s
• 12 s
• 640 s

Answer: 1.6 s. Time period = total time ÷ number of oscillations = 32 ÷ 20 = 1.6 s. 0.625 is what you get by dividing the wrong way round.