Physics Grade 10 Gas laws Ideal gas law Formative assessment (markscheme)

Formative assessment (markscheme)

Cambridge 9702_s05_qp_4              Q2

(a) obeys the law pV/T = constant or any two named gas laws                          M1

at all values of p, V and T                                                                                A1              [2]

or    two correct assumptions of kinetic theory of ideal gas                            (B1)

        third correct assumption                                                                           (B1)

(b) (i) mean square speed                                                                            B1              [1]

(ii)   mean kinetic energy = ½m<c²>                                                              M1

        ρ = Nm/V and algebra leading to [do not allow if takes N = 1]                      M1

        ½m<c²> = 3/2 kT                                                                                     A0              [2]

(c) (i) ½ × 6.6 × 10^-27 × (1.1 ×10⁴)² = 3/2 × 1.38 × 10^-23 × T                                  C1

T = 1.9 × 10⁴ K                                                                                                A1              [2]

(ii) Not all atoms have same speed/kinetic energy                                              B1              [1]