DP Physics (first assessment 2025)

Question 21M.2.SL.TZ1.a.i

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.SL.TZ1.a.i
Level	SL	Paper	2	Time zone	TZ1
Command term	Estimate	Question number	a.i	Adapted from	N/A

a.i.

[Maximum mark: 2]

21M.2.SL.TZ1.a.i

The molar mass of water is 18 g mol⁻¹. Estimate the average speed of the water molecules in the vapor produced. Assume the vapor behaves as an ideal gas.

[2]

Markscheme

E_k = « $\frac{3}{2} (1.38 \times 10^{- 23}) (373)$ » = $7.7 \times 10^{- 21}$ «J» ✓

v = « $\sqrt{\frac{3 \times 1.38 \times 10^{- 23} \times 6.02 \times 10^{23} \times 373}{0.018}}$ » = 720 «m s⁻¹» ✓

Syllabus sections

B. The particulate nature of matter » B.3 Gas laws

Question 21M.2.SL.TZ1.a.i

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