Solved Past Papers + Notes (Relevant to Recent Syllabus)

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Cambridge IGCSE™

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CHEMISTRY 0620/41
Paper 4 Theory (Extended) October/November 2025

1 hour 15 minutes

You must answer on the question paper.

No additional materials are needed.

INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.


INFORMATION
● The total mark for this paper is 80.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.




This document has 16 pages. Any blank pages are indicated.


DC (PB/SW) 347797/4
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1 Protons, neutrons and electrons are particles found in atoms.

(a) Complete Table 1.1 to show the relative mass and relative charge of a proton, a neutron and
an electron.

Table 1.1

particle relative mass relative charge

proton +1




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neutron


electron 1
1840
[2]

(b) Some elements have many isotopes.

(i) Define the term isotopes.

...........................................................................................................................................




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...........................................................................................................................................

..................................................................................................................................... [2]

(ii) Explain why all isotopes of the same element have the same chemical properties.

...........................................................................................................................................

..................................................................................................................................... [1]

(c) Complete Table 1.2.




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Table 1.2

number of number of number of
atom or ion
protons neutrons electrons
40
18Ar 18 18

32 2–
16S 16

22 28 20
[5]
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(d) The term mass number is defined as the total number of protons and neutrons in the nucleus
of an atom.

State the name of one other term which is defined as the total number of protons and
neutrons in the nucleus of an atom.

............................................................................................................................................. [1]

(e) Calculate the number of atoms in 2.00 g of argon.

Give your answer in standard form.
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number of atoms = .............................. [2]

[Total: 13]
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