N-Level Combined Science 3 — Questions and Answers
Question 1: What does the pH scale measure?
- Temperature of a solution
- How acidic or alkaline a solution is (0-14) (Correct answer)
- The density of a liquid
- The concentration of salt in water
Correct answer: How acidic or alkaline a solution is (0-14)
The pH scale measures acidity/alkalinity: 0-6 is acidic, 7 is neutral, and 8-14 is alkaline. Pure water has pH 7.
Question 2: What is the unit of electrical current?
- Volt
- Ohm
- Watt
- Ampere (Correct answer)
Correct answer: Ampere
Electric current is measured in amperes (A), often shortened to 'amps'. An ammeter measures current and is connected in series.
Question 3: What is the role of the stomach in digestion?
- Absorbs nutrients
- Stores bile
- Breaks down food using acid and enzymes (Correct answer)
- Removes water from waste
Correct answer: Breaks down food using acid and enzymes
The stomach churns food and releases hydrochloric acid and enzymes (pepsin) to break down proteins. It acts as a temporary storage and processing chamber.
Question 4: What is an element?
- A mixture of two substances
- A substance made of only one type of atom, which cannot be broken down into simpler substances by chemical means (Correct answer)
- A compound of two elements
- A liquid substance
Correct answer: A substance made of only one type of atom, which cannot be broken down into simpler substances by chemical means
An element is a pure substance made of only one type of atom. It cannot be broken down into simpler substances by chemical reactions. Gold, oxygen, and carbon are examples.
Question 5: Which force acts upward on an object submerged in a liquid?
- Weight
- Friction
- Upthrust (buoyancy) (Correct answer)
- Normal force
Correct answer: Upthrust (buoyancy)
Upthrust (or buoyancy) is the upward force exerted by a fluid on a submerged or partially submerged object, equal to the weight of fluid displaced (Archimedes' principle).
Question 6: What is the difference between a conductor and an insulator?
- Conductors are heavy; insulators are light
- Conductors allow electricity to flow; insulators do not (Correct answer)
- Insulators allow heat to pass; conductors do not
- Conductors are always metals; insulators are always plastic
Correct answer: Conductors allow electricity to flow; insulators do not
Conductors allow electric current to flow through them (e.g., copper, aluminium) due to free electrons. Insulators prevent current flow (e.g., rubber, plastic, glass).
N-Level Combined Science 3
What does the pH scale measure?