O-Level Combined Science 2

Question 1

What is an ionic bond?

Accepted Answer

The electrostatic attraction between oppositely charged ions formed by the transfer of electrons from a metal to a non-metal

Answer

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?

Accepted Answer

To defend the body against pathogens by producing antibodies, engulfing bacteria (phagocytosis), and producing antitoxins

Answer

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?

Accepted Answer

v = f × λ, where v is speed, f is frequency, and λ is wavelength

Answer

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?

Accepted Answer

In series, components are connected end-to-end (same current); in parallel, components are connected across each other (same voltage)

Answer

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?

Accepted Answer

Greenhouse gases (CO₂, CH₄) trap heat radiation from Earth's surface, warming the atmosphere; excessive emissions intensify this effect causing global warming

Answer

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.

GCE O-Level Practice Test

GCE O-Level Practice Test

O-Level Combined Science 2