6.2.1

The Sun as a star

Cambridge IGCSE Physics (0625)  · Unit 6: Space physics  · 4 flashcards

The Sun as a star is topic 6.2.1 in the Cambridge IGCSE Physics (0625) syllabus , positioned in Unit 6 — Space physics , alongside The Earth, The Solar System and Stars.  In one line: The two most abundant elements in the Sun are hydrogen and helium. These elements undergo nuclear fusion, releasing vast amounts of energy.

This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical).

The deck below contains 4 flashcards — 1 definition — covering the precise wording mark schemes reward.  Use the definition card to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.

Key definition

The two most abundant elements that make up the Sun

The two most abundant elements in the Sun are hydrogen and helium. These elements undergo nuclear fusion, releasing vast amounts of energy.

What the Cambridge 0625 syllabus says

Official 2026-2028 spec

These are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.

  1. Know Know that the Sun is a star of medium size, consisting mostly of hydrogen and helium, and that it radiates most of its energy in the infrared, visible light and ultraviolet regions of the electromagnetic spectrum
  2. Know Know that stars are powered by nuclear reactions that release energy and that in stable stars the nuclear reactions involve the fusion of hydrogen into helium Supplement
Definition Flip

What are the two most abundant elements that make up the Sun?

Answer Flip

The two most abundant elements in the Sun are hydrogen and helium. These elements undergo nuclear fusion, releasing vast amounts of energy.

Key Concept Flip

Describe the regions of the electromagnetic spectrum in which the Sun radiates most of its energy.

Answer Flip

The Sun radiates most of its energy in the infrared, visible light, and ultraviolet regions of the electromagnetic spectrum. Infrared radiation is felt as heat, visible light allows us to see, and ultraviolet radiation can cause sunburn.

Key Concept Flip

Explain how the Sun, a stable star, generates its energy. Include the names of the elements involved in the primary nuclear reaction.

Answer Flip

The Sun generates energy through nuclear fusion in its core. Specifically, hydrogen nuclei (protons) fuse together to form helium nuclei. This fusion process releases a tremendous amount of energy in the form of electromagnetic radiation and kinetic energy of the particles. The energy released balances the gravitational forces, creating a stable star.

Key Concept Flip

State the name of the nuclear process that powers the Sun and describe the particles that combine to form helium.

Answer Flip

The nuclear process is called nuclear fusion. Four hydrogen nuclei (protons) combine in a series of steps to form one helium nucleus.

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6.1.2 The Solar System 6.2.2 Stars

Key Questions: The Sun as a star

What are the two most abundant elements that make up the Sun?

The two most abundant elements in the Sun are hydrogen and helium. These elements undergo nuclear fusion, releasing vast amounts of energy.

More topics in Unit 6 — Space physics

The Sun as a star sits alongside these Physics decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.

Key terms covered in this The Sun as a star deck

Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.

The two most abundant elements that make up the Sun

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