Science for grades 3–4: questions with answers
The Science questions for grades 3–4 from the game, with the correct answers and an explanation for each.
How many planets are there in the Solar System?
- 7
- 8
- 9
- 10
Correct answer: 8 — Since 2006 there are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Pluto was reclassified as a dwarf planet.
What is the largest organ of the human body?
- Heart
- Liver
- Skin
- Brain
Correct answer: Skin — An adult's skin weighs around 4 kg and covers about 2 square metres. The liver is the largest internal organ.
Which metal is liquid at room temperature?
- Iron
- Mercury
- Copper
- Lead
Correct answer: Mercury — Mercury melts at about -39 °C, so it stays liquid in normal conditions. It was used in thermometers for centuries before being replaced because it is toxic.
What is the value of pi to two decimal places?
- 2.71
- 3.14
- 3.41
- 4.13
Correct answer: 3.14 — Pi is the ratio of a circle's circumference to its diameter. Its digits go on forever without repeating, and 14 March (3/14) is celebrated as Pi Day.
What is the process by which plants make food using sunlight called?
- Respiration
- Digestion
- Fermentation
- Photosynthesis
Correct answer: Photosynthesis — In photosynthesis, plants use sunlight to turn water and carbon dioxide into sugar, releasing oxygen as a by-product. Nearly all the oxygen we breathe comes from it.
Which unit is used to measure electrical power?
- Volt
- Ampere
- Watt
- Ohm
Correct answer: Watt — The watt is named after James Watt, the Scottish engineer who improved the steam engine. A kilowatt is a thousand watts.
Which is the largest planet in the Solar System?
- Earth
- Saturn
- Jupiter
- Neptune
Correct answer: Jupiter — Jupiter is so large that more than 1,300 Earths would fit inside it. It is a gas giant with no solid surface.
What is the chemical symbol for gold?
- Ag
- Au
- Gd
- Ge
Correct answer: Au — Au comes from aurum, the Latin word for gold. Gold does not rust or tarnish, which is why ancient gold objects still shine.
Which blood cells carry oxygen around the body?
- Red blood cells
- White blood cells
- Platelets
- Plasma
Correct answer: Red blood cells — Red blood cells are packed with haemoglobin, an iron-rich protein that binds oxygen and gives blood its red colour.
What do the three angles of a triangle add up to?
- 90°
- 180°
- 270°
- 360°
Correct answer: 180° — In any flat triangle the angles sum to 180 degrees. On a curved surface such as a globe they can add up to more.
Through which of these can sound NOT travel?
- Water
- Metal
- Rubber
- Vacuum
Correct answer: Vacuum — Sound is a vibration that needs a material to pass through. In the vacuum of space, even an explosion is silent.
The gravitational pull of which body is the main cause of Earth's tides?
- Moon
- Sun
- Mars
- Jupiter
Correct answer: Moon — The Moon's gravity pulls the oceans into a bulge, giving most coasts two high tides a day. The Sun's pull also matters, but less than half as much.
What is the chemical name for table salt?
- Sodium chloride
- Potassium chloride
- Calcium carbonate
- Sodium bicarbonate
Correct answer: Sodium chloride — Table salt is sodium chloride, NaCl. The word 'salary' comes from the Latin word for salt, though the story that Roman soldiers were paid in salt is probably a myth.
How many chambers does the human heart have?
- 2
- 3
- 4
- 6
Correct answer: 4 — The heart has two atria and two ventricles. The right side pumps blood to the lungs, the left side to the rest of the body.
What is a triangle with all three sides equal called?
- Scalene
- Isosceles
- Right-angled
- Equilateral
Correct answer: Equilateral — An equilateral triangle also has three equal angles of 60 degrees each. An isosceles triangle has only two equal sides.
What is the SI unit of force?
- Joule
- Watt
- Pascal
- Newton
Correct answer: Newton — One newton is roughly the force needed to hold a small apple against gravity. The unit is named after Isaac Newton.
Which planet is famous for its bright rings?
- Mars
- Jupiter
- Saturn
- Uranus
Correct answer: Saturn — Saturn's rings are made mostly of ice and rock. They stretch over 280,000 km across but are only tens of metres thick.
Which gas is used in party balloons to make them float?
- Helium
- Oxygen
- Nitrogen
- Argon
Correct answer: Helium — Helium is lighter than air and does not burn, unlike hydrogen. It is the second most abundant element in the universe.
Which of these materials conducts electricity best?
- Rubber
- Wood
- Glass
- Copper
Correct answer: Copper — Copper is used in most electrical wires because it conducts electricity very well and is cheaper than silver, the best conductor.
What do we call a number divisible only by 1 and itself?
- A prime number
- An even number
- An odd number
- A square number
Correct answer: A prime number — The prime numbers begin 2, 3, 5, 7, 11, 13. There are infinitely many of them, as Euclid proved over 2,000 years ago.