Combined Science Flashcards

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

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)

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

What is Ohm's Law?

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

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.

What is the difference between an exothermic and endothermic reaction?

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

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

What is osmosis?

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

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).

What is the law of reflection?

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

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.

What is the role of enzymes in the human digestive system?

Answer: They are biological catalysts that speed up the breakdown of food molecules into smaller, absorbable units

Digestive enzymes are biological catalysts: amylase breaks down starch to maltose, protease breaks proteins into amino acids, and lipase breaks fats into fatty acids and glycerol.