O-Level Combined Science 2 — Questions and Answers
Question 1: What is an ionic bond?
- Sharing of electrons between atoms
- The electrostatic attraction between oppositely charged ions formed by the transfer of electrons from a metal to a non-metal (Correct answer)
- A bond between two non-metals
- A weak intermolecular force
Correct answer: The electrostatic attraction between oppositely charged ions formed by the transfer of electrons from a metal to a non-metal
Ionic bonding occurs when a metal atom transfers electrons to a non-metal atom, forming positive and negative ions. The strong electrostatic attraction between these ions constitutes the ionic bond.
Question 2: What is the function of white blood cells in the immune system?
- To carry oxygen
- To defend the body against pathogens by producing antibodies, engulfing bacteria (phagocytosis), and producing antitoxins (Correct answer)
- To transport nutrients
- To clot blood
Correct answer: To defend the body against pathogens by producing antibodies, engulfing bacteria (phagocytosis), and producing antitoxins
White blood cells (leukocytes) protect the body in multiple ways: phagocytes engulf and digest pathogens, while lymphocytes produce specific antibodies that target and neutralise particular pathogens.
Question 3: What is the relationship between speed, frequency, and wavelength of a wave?
- v = f + λ
- v = f × λ, where v is speed, f is frequency, and λ is wavelength (Correct answer)
- v = f / λ
- v = f² × λ
Correct answer: v = f × λ, where v is speed, f is frequency, and λ is wavelength
The wave equation v = fλ relates speed (m/s), frequency (Hz), and wavelength (m). This applies to all waves including sound, light, and water waves.
Question 4: What is the difference between a series and parallel electrical circuit?
- They are identical
- In series, components are connected end-to-end (same current); in parallel, components are connected across each other (same voltage) (Correct answer)
- Series circuits have no resistance
- Parallel circuits only have one path
Correct answer: In series, components are connected end-to-end (same current); in parallel, components are connected across each other (same voltage)
In series: one path for current (same I throughout), voltages add up. In parallel: multiple paths (same V across branches), currents add up. Parallel circuits keep working if one branch breaks.
Question 5: What is the greenhouse effect and how does it relate to climate change?
- Only occurs in greenhouses
- Greenhouse gases (CO₂, CH₄) trap heat radiation from Earth's surface, warming the atmosphere; excessive emissions intensify this effect causing global warming (Correct answer)
- It cools the Earth
- It only affects polar regions
Correct answer: Greenhouse gases (CO₂, CH₄) trap heat radiation from Earth's surface, warming the atmosphere; excessive emissions intensify this effect causing global warming
The greenhouse effect is natural and necessary. However, increased emissions of CO₂ (from burning fossil fuels) and CH₄ (from agriculture) enhance this effect, leading to global warming and climate change.
Question 6: What is the structure and function of the human heart?
- A single-chambered pump
- A four-chambered muscular organ that pumps oxygenated blood to the body (left side) and deoxygenated blood to the lungs (right side) (Correct answer)
- A three-chambered organ
- A passive organ that does not pump
Correct answer: A four-chambered muscular organ that pumps oxygenated blood to the body (left side) and deoxygenated blood to the lungs (right side)
The heart has four chambers: right atrium and ventricle (pump deoxygenated blood to lungs) and left atrium and ventricle (pump oxygenated blood to the body). Valves prevent backflow.
