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 (COâ‚‚, CHâ‚„) 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 (COâ‚‚, CHâ‚„) 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 COâ‚‚ (from burning fossil fuels) and CHâ‚„ (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.
O-Level Combined Science 2
What is an ionic bond?