CIE iGCSE Co-Ordinated Science P1.6.4 Power Exam Style Questions Paper 4

(a)(i) Z reduces by 2; neutrons reduce by 2; A reduces by 4

An alpha particle consists of 2 protons and 2 neutrons (like a helium nucleus).
Emitting one therefore reduces the proton number (\( Z \)) by 2, the number of neutrons by 2, and the nucleon number (\( A \)) by 4.

(a)(ii) \( 13.9 \, \text{s} \)

87.5% tin means 12.5% tellurium-109 remains.
\( 100\% \rightarrow 50\% \rightarrow 25\% \rightarrow 12.5\% \) is 3 half-lives.
Time \( = 3 \times 4.63 = 13.9 \, \text{s} \).

(b)(i) Advantage: no CO₂ emissions; Disadvantage: doesn’t work at night

Solar cells generate electricity without producing carbon dioxide or contributing to climate change.
However, they don’t generate electricity at night, and require a large surface area to produce significant power.

(b)(ii) Black absorbs light/radiation well

A black surface is a good absorber of light and thermal radiation, meaning more of the incoming solar energy is absorbed rather than reflected, improving efficiency.

(b)(iii) \( 168 \, \text{W} \)

Area of the panel \( = 1.5 \times 0.5 = 0.75 \, \text{m}^2 \).
Power input \( = 1400 \times 0.75 = 1050 \, \text{W} \).
Power output \( = 1050 \times 0.16 = 168 \, \text{W} \).