N-Level Science — Questions and Answers
Question 1: What is the chemical formula for water?
- CO₂
- H₂O (Correct answer)
- NaCl
- O₂
Correct answer: H₂O
Water's chemical formula is H₂O, meaning each molecule consists of two hydrogen atoms bonded to one oxygen atom through covalent bonds.
Question 2: What is photosynthesis?
- The process by which animals breathe
- The process by which green plants use sunlight to convert carbon dioxide and water into glucose and oxygen (Correct answer)
- The process of digesting food
- The process of evaporation
Correct answer: The process by which green plants use sunlight to convert carbon dioxide and water into glucose and oxygen
Photosynthesis is the process: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. It occurs in chloroplasts using chlorophyll to capture light energy and convert it into chemical energy stored in glucose.
Question 3: What is the SI unit of force?
- Joule
- Watt
- Newton (Correct answer)
- Pascal
Correct answer: Newton
The SI unit of force is the newton (N), named after Sir Isaac Newton. One newton is the force needed to accelerate a mass of 1 kg by 1 m/s².
Question 4: In the human body, what is the function of red blood cells?
- To fight infections
- To transport oxygen from the lungs to body tissues using haemoglobin (Correct answer)
- To clot blood at wound sites
- To digest food
Correct answer: To transport oxygen from the lungs to body tissues using haemoglobin
Red blood cells contain haemoglobin, which binds to oxygen in the lungs and transports it to cells throughout the body. They are biconcave in shape to maximise surface area for gas exchange.
Question 5: What is an electric circuit?
- A type of sports track
- A closed loop through which electric current can flow, consisting of a power source, conductors, and electrical components (Correct answer)
- Any piece of wire
- A type of battery
Correct answer: A closed loop through which electric current can flow, consisting of a power source, conductors, and electrical components
An electric circuit is a complete closed path that allows electric current to flow from a power source (battery), through conductors (wires) and components (bulbs, resistors), and back to the source.
Question 6: What happens to the temperature of a substance during a change of state (e.g., melting)?
- Temperature increases rapidly
- Temperature remains constant as energy is used to break intermolecular bonds rather than increase kinetic energy (Correct answer)
- Temperature decreases
- Temperature fluctuates randomly
Correct answer: Temperature remains constant as energy is used to break intermolecular bonds rather than increase kinetic energy
During a change of state, the temperature stays constant even though heat is being absorbed. The energy goes into breaking the forces between particles rather than increasing their kinetic energy.
N-Level Science
What is the chemical formula for water?