Text Links: Home Lesson Plans Humor Teacher Inquiry Urban Education Web Wizardry Links All material is my personal opinion, and not that of any other organization. Copyright 2001. Permission is granted for individual teacher use. All rights reserved. Feedback is invited: Email me!

Investigating Density: Heavy Ice Note: There is a much expanded version of this lesson that I have published as part of an 8th grade lesson sequence, with contributions from others. Overview: This lesson is a highly structured introduction to scientific investigation, focused on the concept of density. Student interest is engaged with a discrepent event, and then students experiment with different combinations of objects and liquids of various densities. They end up learning the formula for density and calculate the densities of various materials, and predict if they will sink or float. Target: Grades 6 to 9 Day 1: What is an Observation? Materials For the Teacher: Two clear glass 250 or 500 ml beakers, labelled A and B Two+ ice cubes (you should have extras) 200 ml of alcohol, isopropyl or ethanol 200 ml of water Procedure Step One: Begin by telling students: The most important tool a scientist has is his or her powers of observation. So today, we are going to stretch and build those powers. Reveal to the students two identical beakers, one containing about 200 ml of alcohol, the other containing the same amount of clear water. Ask them to record in writing as many detailed observations as they can. They can also include a sketch. You can walk around the room holding the beakers out before the students, but do not let them sniff them, as the odor will spoil the surprise later. When students are done writing, ask for their observations, and record them on the board or on the overhead. Step Two: Show them the two ice cubes. Pose the question; "What will happen if the ice is placed in the beakers?" Ask for predictions and hypotheses, and record them on the board. Have students write down their personal prediction. Point out that our next step is a test. The ice is placed in each liquid. It sinks in alcohol, and floats in water. Circulate in the room, asking them to sketch what they see, and record detailed observations. Step Three: What did you "observe"? Review the initial observations the students made. Point out the distinction between true observations, such as "There is clear liquid in each beaker" and statements such as "there is water in each beaker." The second statement is an inference, which means it is a judgement we have made, drawn from our observations. One of the things scientis do is to make inferences, but we need to check those inferences, which is one reason we do experiments. (Note: Astute observers may pick up on some other details that are quite informative. For example, the ice in alcohol will, after a few minutes, begin to melt, and actually float up off the bottom on a layer of water. This layer will be colder than the alcohol above, so students may notice condensation on the bottom part of the beaker only. These observations may help the students later.) On to Day 2: Generating New Questions Day 3: Magic Time! Day 4: Liquids of Different Densities Day 5: Objects of Different Densities Day 6: Assessment