Look for: Which sample is less dense?

5.A.1 Conduct investigations to collect and use observations and data as evidence to determine the effects of thermal energy transfer to the air in contact with Earth’s surface.

After the scenario is presented, students are directed to talk with a partner and make a claim supported with evidence. Listen for the following ideas to surface:

Which sample is less dense?

• Sample A has a greater number of molecules in the same amount of space as Sample B.
• Sample B is less dense than Sample A because it has fewer molecules that are less densely packed in the same size space.

What caused this difference?

• The ground in direct sunlight receives more sunlight than the ground in the shade.
• The blacktop absorbs more sunlight and gets warmer.
• The air is heated through direct contact with the ground (conduction).
• The air over the blacktop gets warmer than ___, because the blacktop has more thermal energy than ___.
• The molecules that make up the air over the blacktop have more energy, move faster, and spread farther apart, so the air in Sample A is less dense than the air in Sample B.

If students struggle with the term density, use the phrase “amount of matter in a given space” or “how closely packed together the particles are” to help them think about density in conceptual terms. If they need additional scaffolding, use questions to help guide their thinking. For example, ask, What is the same about both samples? What is different? Which of these differences is causing the air to look different in each sample? If students need help formulating a claim with evidence and reasoning, use sentence starters, such as Sample ___ is less dense because ___________. When a sample of the same type of matter is less dense than another sample of that matter, the particles that make it up _________________.