A student compared two fertilizer amounts, but also put one pot on a sunny sill and the other in a dim corner. Why can the growth difference not be blamed on the fertilizer?

A class dropped a ball onto sand from 1 m and measured a 2 cm crater. They then dropped a heavier ball from 3 m and measured a 5 cm crater. What can these two results not show?

Group A stirred 5 g of sugar into 100 mL of water at 20 C, ten stirs. Group B stirred 10 g into 100 mL at 60 C, ten stirs. Why can their dissolving times not be used to compare the two water temperatures?

A team tests a plant food on tomato plants. One group gets the plant food. Another group, kept in the same light, soil and water, gets none. Why does the team keep a group with no plant food?

A toy car rolled off a ramp in five trials, traveling 17 cm, 22 cm, 20 cm, 24 cm and 22 cm. The mean is 21 cm. What conclusion do all five trials together best support?

Four thermometers placed in different spots in one room read 21.0 C, 21.5 C, 21.2 C and 34.0 C within the same minute. What should the class do about the 34.0 C reading?

Across one summer, weekly ice-cream sales and the weekly number of swimmers at a lake both rose. What can the class fairly claim from these data?

One group rolled a ball down a ramp once and reported 21 cm. A second group rolled it five times and reported the mean. Why is the second result stronger evidence?

Nitrate readings downstream of a farm were 8, 9 and 3 mg/L. Readings upstream were 2, 2 and 7 mg/L. What claim do these data best support?

Two web pages disagree about a lake's oxygen level. One is a fertilizer company blog with no data. The other is a university report showing its data table and methods. Which is the more credible source?

A class claims an insulating sleeve keeps cocoa hot longer, but they tested one sleeved cup and one bare cup on different days. What extra evidence would best settle the claim?

A student writes two notes: 'the liquid turned cloudy blue' and 'the liquid cooled from 40 C to 31 C'. How should the two notes be classified?

A student found an odd-shaped rock's volume by water displacement in a graduated cylinder. He then recorded the rock's mass by hanging it from a spring scale marked in newtons. What can his data still show?

Before pouring a warm liquid, a student pushes her goggles onto her forehead and leans over the beaker to smell it. What did her procedure get wrong?

A class plotted pond temperature every hour for eight hours on a line graph. The line rises from 08:00 to 14:00, dips at 15:00, then rises again to 16:00. What claim does the graph best support?

A class model shows a stream carrying all of its sediment straight to the sea. New measurements show most sediment settles behind a bend. How should the class respond?

A student wants a question about bean seeds that an investigation could settle without any further wording being fixed first. Which question is already measurable as it stands?

Team A records the water depth at twenty points across a pond and maps the pond floor. Team B grows pond plants at three light levels and compares their growth. How do the two studies differ?

A class predicted before testing that warmer water dissolves sugar faster, but their trials showed no difference. Because the data did not match, their prediction was never a scientific hypothesis.

A student claims a useful model must include every detail of the real system it represents. What is the flaw in that claim?