Assessed homework - radioactivity

1.       (a)     protons/p;                                                                                                         1
[Reject protons and neutrons]

(b)     negative/ -1 / e- /minus;                                                                                    1

  (c)   An explanation to include:

          1. positive;
2. lost a negative charge/more protons than electrons;                             2
[Reject lost an electron]

(d)     no of protons = no of electrons = 3;
no of neutrons = 7 – 3 = 4;                                                                               2
[bald correct answer, 2 marks]

[6]

 

  2.     (a)     gamma;                                                                                                             1

(b)     (i)      beta;                                                                                                        1

(ii)     An explanation to include:

          1. alpha would not penetrate/alpha all absorbed/alpha
    stopped by paper/eq;
2. all gamma would penetrate (too much)/gamma not absorbed;

          [Accept alpha not strong enough and gamma is too strong/eq for 1 max] 2

[4]

 

  3.     (a)     positive;
negative;
none;
(Be wary of the ‘dash’ for g)                                                                            3

  (b)   does not penetrate the air/casing/easily stopped/OWTTE;
strongly ionising/very good at ionising/lots of ion pairs;
[Reject least harmful/least dangerous]                                                              2

[5]

 

  4.     (a)     (i)      axis labelled;
points correctly plotted;
line drawn through points;                                                                       3

  (ii)   linear / proportional relationship stated;                                                  1

  (iii)  hair loss / sterility / nausea / radiation burns;                                           1

  (b)   much stronger ioniser than other two;
more thermal energy generated in passing through material;                             2

[7]

 

  5.     C

[1]

 

6.       (a)     more than one tick per horizontal row negates that row
most penetrating – gamma
least penetrating – alpha
most ionising – alpha
least ionising – gamma
Any one correct row; (1 mark)
All 4 rows correct;;                                                                                         2

  (b)   gamma
most penetrating/greatest range;                                                                        1

Allow least ionising so safer

  (c)   protons =27
electrons = 27
neutrons = 33
Any one correct; (1 mark)
All 3 correct;;                                                                                                  2

  (d)   (performance) cobalt
penetration OR time to scan;                                                                            1

Ignore x-rays

          (safety) cobalt
faster;                                                                                                               1

Allow X ray lower energy

Ignore references to penetration

[6]

 

7.       (a)     (idea of) time for half of undecayed nuclei/atoms to decay
OR (idea of time) for radioactivity/count rate halved;                                      1

(reject mass changes)

(b)     1000÷2 [any other value (in range 500-1000)÷2];                                            2

(check graph)

          50 (47-53) (min);

(ignore unit)
(or alternative calculation for 2 marks)
[Reject 100/2 =50 for both marks]

(c)      (i)      2 (Bq);                                                                                                     1

(ignore units)

(ii)     any two from:
contamination idea;

e.g. still waste there/soil contaminated

          opinion/perception of risk/worry/fright;
radioactivity can be harmful/dangerous/cause cancer/mutations;
2 Bq (or ecf from (c)(i)/only 2 half lives/remains radioactive for long time;           2

[6]