GCSE GCSE Combined Science 3

Question 1

What is the difference between a covalent bond and a metallic bond?

Accepted Answer

A covalent bond involves sharing electrons between non-metals; metallic bonds involve delocalised electrons in a lattice of metal ions

Answer

Covalent bonds form when non-metal atoms share electrons. Metallic bonds involve a lattice of positive metal ions surrounded by a 'sea' of delocalised (free-moving) electrons. The electrostatic attraction between ions and electrons holds metals together.

Question 2

What is the difference between series and parallel circuits?

Accepted Answer

In series, current flows in one path; in parallel, current can flow through multiple paths simultaneously

Answer

In a series circuit, components are connected end-to-end in a single loop; current is the same throughout. In a parallel circuit, components have separate branches; current splits between branches, but voltage across each branch is the same.

Question 3

What is natural selection?

Accepted Answer

The process by which organisms with favourable traits are more likely to survive, reproduce, and pass on those traits

Answer

Natural selection (Darwin's theory): individuals with traits better suited to their environment are more likely to survive and reproduce, passing on advantageous genes. Over generations, favourable traits become more common.

Question 4

What is the equation for calculating work done?

Accepted Answer

Work = force × distance

Answer

Work done (measured in Joules) = Force (N) × Distance (m). Work is done when a force causes displacement in the direction of the force. If no displacement occurs, no work is done.

Question 5

What is the difference between a physical and a chemical change?

Accepted Answer

Physical changes are always reversible; chemical changes produce new substances and are usually irreversible

Answer

In a physical change, the substance itself doesn't change (melting ice, dissolving sugar) — it is usually reversible. In a chemical change, new substances are formed (burning, rusting, digestion) — usually irreversible.

GCSE Revision Practice Test

GCSE Revision Practice Test

GCSE GCSE Combined Science 3