O-Level Combined Science

Question 1

What is an atom and what are its three main subatomic particles?

Accepted Answer

An atom is the smallest unit of an element, consisting of protons (positive, in nucleus), neutrons (neutral, in nucleus), and electrons (negative, orbiting the nucleus)

Answer

An atom has a dense nucleus containing positively charged protons and neutral neutrons, with negatively charged electrons orbiting in shells around the nucleus.

Question 2

What is Ohm's Law?

Accepted Answer

V = I × R, where V is voltage (volts), I is current (amps), and R is resistance (ohms)

Answer

Ohm's Law states that voltage (V) equals current (I) multiplied by resistance (R). This fundamental relationship applies to many electrical circuits and is essential for O-Level Physics.

Question 3

What is the difference between an exothermic and endothermic reaction?

Accepted Answer

Exothermic reactions release heat to surroundings (temperature rises); endothermic reactions absorb heat from surroundings (temperature drops)

Answer

Exothermic reactions release energy (e.g., combustion, neutralisation — surroundings get warmer). Endothermic reactions absorb energy (e.g., thermal decomposition, photosynthesis — surroundings get cooler).

Question 4

What is osmosis?

Accepted Answer

The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane

Answer

Osmosis is the passive movement of water molecules through a partially permeable membrane from a dilute solution (high water potential) to a concentrated solution (low water potential).

Question 5

What is the law of reflection?

Accepted Answer

The angle of incidence equals the angle of reflection, both measured from the normal to the reflecting surface

Answer

The law of reflection states that the angle of incidence (incoming ray to normal) equals the angle of reflection (reflected ray to normal). The incident ray, reflected ray, and normal are all in the same plane.

GCE O-Level Practice Test

GCE O-Level Practice Test

O-Level Combined Science