Question

You are a forensic scientist working at a crime scene outside along a fairly busy road. It is late at night and it is beginning to rain. You must finish what you are working on before the rain ruins the evidence. Because it is dark, you are afraid you will be hit by a passing car and decide to set up flares to divert traffic around the area. The labels on the flares have been partially torn and you cannot read which ones will burn when wet, so you look at the ingredient label on each one for a clue. Which flare should you use?

A. Flare 3 contains potassium (K).
B. Flare 4 contains sulfur (S).
C. Flare 2 contains zinc (Zn).
D. Flare 1 contains magnesium (Mg).

Answer 1

Flare 1 containing magnesium (Mg) should be used since magnesium burns brightly even in wet conditions, ensuring visibility and safety at a rainy, nighttime crime scene.

Step-by-step explanation:

Among the flares listed, Flare 1 containing magnesium (Mg) should be used since magnesium will burn brightly even when wet, providing visibility and safety in your scenario. When looking at the properties of common elements used in flares, magnesium stands out because colorful fireworks often involve the reaction of metals with oxygen, including magnesium, which produces a bright flame that is visible even in adverse weather conditions. Magnesium reacts with oxygen to form magnesium oxide with a bright white flame, making it suitable for use in wet conditions. The reference to potassium (Flare 3) being stored under kerosene or oil because of its high reactivity with water suggests that it is not ideal for use in the rain. Similarly, sulfur (Flare 4) is not characterized for use in wet conditions in the given context, and zinc (Flare 2) requires heat for a vigorous reaction as indicated in the zinc sulfide formation experiment.