OpenSciEd Unit 7.1 · Lesson 04 · 4.A
Look for: all the possible combinations of substances t…
From Teacher Edition
Facilitation guidance from the lesson plan — what to notice in student thinking and how to respond while teaching.
Building towards
4.A.1 Conduct an investigation to produce data to serve as the basis for evidence to determine which combinations (patterns) of substances in a bath bomb cause bubbles of gas to appear (effect).
What to look / listen for
On day 1, listen for discussions about how data are needed to support a claim:
all the possible combinations of substances that need to be tested [9 x 9 = 81]
possible redundancies with some combinations
making predictions about the patterns of causes (combinations) and effects (bubbles) they expect to see
What to do
If students are struggling to consider the number of combinations or redundancies, you may want to talk through creating a chart with them rather than jumping to the one you already have prepared.
Give students about 3–4 minutes to get into small groups and discuss the following questions on slide D:
What are we hoping to figure out by testing combinations of these different ingredients?
What evidence are we looking for to help figure that out?
How many different possible combinations will we have if we combine them two at a time to water?
Prepare for the investigation. Say, I have a chart listing each of these 10 ingredients in each row and in each column. Let’s see if we can use it to reason out how many unique combinations there are for us to try.
Distribute a copy of Combinations of Ingredients to Test to each student. Display slide E. Say, I was thinking we could have 10 groups, and each group could test all the combinations for a row in this table. For example, group 1 could test coconut oil, which is listed at the start of their row, with each of the ingredients listed at the tops of the 10 columns.
Ask, Does anyone see any combinations in this row that it wouldn’t make sense for this group to do? Students will say, Coconut oil with coconut oil.
Point out that this sort of redundancy might be in other rows too. Mark Xs in these boxes together as you identify them as a class, as shown below.✱
Say, This leaves 9 combinations for each group to try. I will give each group an ice cube tray like this one, which has 12 spots in it. Hold up an ice cube tray to show the class.
Say, This will allow each group to test the 9 combinations they are assigned from their row. So, let’s assign the groups now.