Mia asks whether warm water dissolves salt faster than cool water. She uses two cups with the same salt and stirring. What should she change?

A class tests whether grass roots slow erosion. They pour water on a bare soil tray and a grass-covered soil tray. What must stay the same?

Noah wants to learn whether a thicker wire affects how bright a bulb looks in a simple circuit. What should he change?

Lena asks whether larger sugar pieces dissolve more slowly. She puts sugar cubes and crushed sugar into equal water. What should she measure?

A student tests whether a ball rolls farther down a steeper ramp. What should stay the same in each trial?

Priya asks whether more sunlight helps bean plants grow taller. She puts plants near a window and in shade. What should she keep the same?

Eli wants to test whether a magnet picks up more paper clips through thin cardboard or thick cardboard. What should he change?

A class compares how quickly ice melts on black paper and white paper under a lamp. What should stay the same for a fair test?

Jo tests whether steep slopes erode faster. She uses a steep tray with sand and a flat tray with soil. Why can she not answer her question?

Marco asks whether warm water dissolves sugar faster. He puts sugar in warm water and salt in cool water. What is unfair about his test?

A group tests whether more water helps radish plants grow taller. One plant gets more water and more sunlight. Why is the test unfair?

Sam tests whether a thicker wire changes bulb brightness. He uses a thick wire with a new battery and a thin wire with an old battery. What is the problem?

Tara asks whether a hand lens helps see rock grains. She compares a dry rock by eye with a wet rock through the lens. Why is this unfair?

A class asks whether salt makes ice melt faster. One cup has ice with salt in sunlight, and one has plain ice in shade. Why can the result not answer the question?

A globe helps students study Earth’s shape and oceans. They want to plan a walking route across town. What limitation matters most?

A clay volcano model shows the cone shape and flowing lava. Students want to find out how soon a real volcano near a town might blow its top. Which limitation matters most?

A stream table shows water carrying sand down a slope. Students want to learn how a river moves rocks as big as a car. Which limitation matters most?

A water cycle diagram shows clouds and rain falling. Students want to know exactly how much rain fell on their school this morning. Which limitation matters most?

A paper circuit diagram shows a battery, wires, switch, and bulb. Students want to know if the real bulb feels warm. Which limitation matters most?

A plastic skeleton model shows many bones in the human body. Students want to learn how a pitcher's arm moves when throwing a ball. Which limitation matters most?