Question

moji listed the solids in order of hardness as graphite < chalk < quartz. his peer group suggested some experimental errors that may have caused this to happen. which experimental error most likely led moji to this conclusion?
a. moji might have used color as an indication of hardness.
b. moji could have chosen hardness tests that were not reliable.
c. moji might have thought that crumbliness was a sign of softness.
d. moji might have thought that crumbliness was a sign of hardness.

Explanation:

Hardness is a measure of a material's resistance to being scratched or indented. Graphite is a soft mineral, chalk is also relatively soft but harder than graphite, and quartz is a hard mineral. If Moji thought that crumbliness was a sign of softness, he might have misjudged the hardness. Graphite is crumbly (soft), chalk is less crumbly (harder than graphite), and quartz is not crumbly (hard). Option A: Color has no relation to hardness. Option B: If the hardness tests were not reliable, it's a broad error but not the most likely specific one here. Option D: Thinking crumbliness is a sign of hardness would lead to the opposite conclusion.

Answer:

C. Moji might have thought that crumbliness was a sign of softness.