Look for: Q1) The density of the clear liquid is close…

9.A.2 Use mathematical and computational thinking by graphing mass vs. volume data for different substances and finding the ratio of mass to volume (a unit rate) (scale, proportion, quantity) for the samples measured to determine the density of different clear liquids.

The following responses on student index cards:

Q1) The density of the clear liquid is close to 1.0 grams per mL

Q2) The same density as in Q1 (1.0 grams per mL).

If students struggle with determining or using unit rates in the context of density you could:

• Provide additional measurements of water or alcohol for students to practice finding unit rates.
• Coordinate with the grade level math teacher to provide other examples and practice finding unit rates students have been working with (or will be working with) in math class.
• Ask, Is the density of this liquid similar to any of the three known clear liquids? Students should say that it is very close to the density of water (1.0 g/mL).
• Identify and mark the coordinates for this data point (volume, grams) on the water graph for the sample you just measured. Show that the same coordinate on the other graphs does not match the linear trend in the data plotted on those graphs.

Say, It seems like the graphs and tables that helped us find the density of each liquid also provide us strong evidence about what the unknown clear liquid is. I think we can use this and our earlier observations about the other properties of that gas to make some evidence based arguments about whether or not the gas we collected is made of a different type of particle (a new substance) than the water we started with.

Ask students to turn and talk with an elbow partner for a minute about this question before heading back to their seats.