A student claims that adding compost makes bean plants grow taller. The class grew bean plants with compost and identical plants without it. Which result would best support the claim?

Maya claims that warmer water dissolves sugar faster. Her group stirred one spoon of sugar the same way in water at 20 C and at 60 C. Which result would weaken her claim?

Two groups disagree about whether a wool sleeve keeps cocoa hot longer than a paper sleeve. One group started at 70 C and the other at 55 C. What evidence would best settle the disagreement?

In one town, ice-cream sales and the number of reported sunburns both rise steadily from May to July. What is the strongest conclusion from these data?

A class is checking the claim that a nearby lake has healthy water. Which source is the most credible for that claim?

A class wraps identical cups of hot water in 0, 2, 4 or 6 paper layers and records how long each cup stays above 40 C. What is the independent variable?

A group releases the same toy car from ramp heights of 10 cm, 20 cm and 30 cm and measures how far the car rolls on the floor. What is the dependent variable?

A class tests whether more daily light grows taller seedlings. Pots get 4, 8 or 12 hours of light. Which variable must be kept the same for every pot?

One tray of radish seedlings gets fertilizer and an identical tray gets none but is treated the same in every other way. What does the untreated control group let the class rule out?

A class wants to know whether salt water freezes more slowly than fresh water. Which plan is a fair test of that question?

A marble rolls down a ramp in four trials and travels 8 cm, 10 cm, 9 cm and 13 cm past the end of the ramp. What is the mean distance for these trials?

A group heats water on a hot plate and records 22 C, 23 C, 22 C, 41 C and 23 C at the same moment in five trials. What is the most likely source of error in the fourth trial?

A claim is better supported by the mean of five repeated trials than by the result of a single trial.

A report begins, 'The wool sleeve keeps cocoa hot for longer than the paper sleeve.' Which part of a scientific argument is that statement?

A group's report states, 'After 20 minutes the wrapped cup read 58 C and the bare cup read 47 C.' Which part of a scientific argument is that statement?

While testing a mixture, a student writes in the data table, 'the liquid turned cloudy and pale blue.' What kind of data is that observation?

Evidence that disagrees with a claim should be left out when writing up a scientific argument.

A line graph of one pond shows the water temperature rising from 8 C in March to 24 C in July, then falling to 9 C in November. Which conclusion do these data support?

A class wants a question it can answer with a comparative investigation and measurements. Which question can they investigate that way?

Before pouring hot water into a beaker, a student puts on goggles and ties back her long hair. What do these safety procedures mainly protect against?