Sugar is stirred into water in a sealed jar until it cannot be seen. The jar weighs the same before and after. Maya claims the sugar is gone. Ravi claims the sugar is still there. Which claim does the evidence support?

Lena claims a heavy ball always lands before a light one. Tomas claims they land together. The class drops a heavy ball and a light ball from the same height, and both hit the ground at the same moment. Which claim does the evidence support?

A potted plant gained about two kilograms over a summer, but the dry soil in the pot lost only a few grams. Ana claims the new material came from the soil. Devi claims it came mostly from air and water. Which claim fits the data?

The Sun looks far brighter in our sky than any other star. Maya says that is because the Sun is much closer to Earth. Deshawn says it is because the Sun is the biggest, brightest star there is. Whose claim better explains the observation, and why?

Aki claims most of Earth's water is fresh water sitting in rivers and lakes. Bea claims most of Earth's water is salt water in the ocean. Which claim do measurements of Earth's water support?

To test which soil grows taller bean plants, Kai put sandy soil on a sunny sill and potting soil in a dark closet. The potting-soil plants grew taller. What should the class say about Kai's claim that potting soil grows taller plants?

Students want to find out whether a paper cup or a plastic cup keeps water warm longer. They start with water at the same temperature in both cups and set both cups in the same room. What else must they keep the same in both cups?

Repeating an investigation several times and getting the same result gives stronger evidence for a claim than doing it only once.

Two classmates give opposite reasons for why a plant left in a dark closet turned pale. What should decide which claim the class accepts?

Two students can read the same data table and still make different claims about what the measurements mean.

Air is sealed inside a syringe with the tip blocked. The plunger can be pushed partway in, and no air escapes. Rosa claims some air was destroyed. Ken claims the air was squeezed into a smaller space. Which claim does the evidence support?

A shallow dish of salt water sits on a sunny sill. Days later the water is gone and white salt is left in the dish. Nia claims the heat destroyed the salt. Omar claims the water evaporated and left the salt behind. Which claim fits the observation?

A stick's shadow measured 40 centimeters at 9 a.m. and 15 centimeters at noon on the same day. Jo claims shadows are longest at noon. Sam claims shadows get shorter toward noon. Which claim do the measurements support?

Dead leaves pile up on a forest floor, and worms and fungi slowly break them apart. Ito claims decomposers make brand new material for the soil. Mia claims they return the leaves' material to the soil. Which claim fits how matter cycles?

Two gray samples look alike. A magnet attracts neither one. In a battery-and-bulb circuit the bulb lights with sample A but stays dark with sample B. What do these results show?

Vinegar poured on baking soda fizzes and gives off gas. In a second cup, salt stirred into water disappears from sight. Priya claims a new substance formed in both cups. Which claim do the observations support?

A river runs through a deep valley it has cut into rock over thousands of years. Ida claims the rock made the river appear. Sam claims the flowing water wore the rock away. Which claim does the evidence support?

Once a class has accepted a claim, it should never change, even if new evidence goes against it.

A class tests whether a lid keeps water warm longer. One cup holds 200 mL of hot water with a lid, and the other holds 100 mL and is left open. The lidded cup stays warmer. Why can the class not yet credit the lid?

Two classes measure the shadow of the same pole at noon on the same day and get 15 cm and 28 cm. What is the best next step before either class states a claim?