Great Lesson Ideas: Testing Liquids for Startch with John Orsulak

Orsulak: [00:00:08] Hi, I’m John Orsulak. I’m a fifth grade science teacher in the Sino Trojan Academy here at Jenks East Intermediate in Jenks, Oklahoma. Welcome. [00:00:16]

[00:00:17] Okay we’re going to talk about starch today. This lesson is a test of starch; seeing if there’s starch present in liquids. [00:00:24]

[00:00:26] I want you to take a moment, turn to your neighbor, tell them something you know about starch. Go. [00:00:32]

Child: [00:00:33] It fights in nutrients. They help you digest. [00:00:36]

Orsulak: [00:00:39] First we talk about and review what starch is; what it contains. We take some time to share with one another what we already know about starch. [00:00:48]

[00:00:48] Today we’re testing liquids for the presence of starch. Our indicator is iodine. All right. What do we mean by an indicator? Let’s review that term. What is an indicator? What does an indicator do? Ross. [00:01:04]

Child: [00:01:05] It shows us if it has starch or not. [00:01:08]

Orsulak: [00:01:08] All right, it’s something that helps us see whether that new particular nutrient is present in the food or the liquid. We know we’re looking for a positive result, it’s going to be—[00:01:19]

Child: [00:01:19] Purplish. [00:01:19]

Orsulak: [00:01:20] The dark purpley black, and if it is a negative, what will we see? Sophie? [00:01:25]

Child: [00:01:26] We will see the [inaudible 01:27]

Orsulak: [00:01:28] All right it will be more of the iodine color. There won’t be a color—a major color change. We know what we’re looking for. We know what starches do, so now we’re going to test six different liquids to see if they have starch in them. So we need to get ourselves organized. [00:01:44]

[00:01:44] I split the jobs into three positions. [00:01:47]

[00:01:47] One job is we remember is the scribe. The scribe will get their netbook; they’ll bring it to their desk. I have sent you through your email the lab sheet for this lab, so you’ll need to pull it up, download it. [00:01:59]

[00:02:00] They are the recorder. They take care of all the record keeping and also sending the data to their classmates via email. [00:02:07]

[00:02:07] Material handlers, you’ll go over to the back table. You’ll get your tubs, two paper towels, the bottles. [00:02:15]

[00:02:15] So everything else is there including the iodine indicator. Then our setup/clean up people are responsible for the actual preparation of the space and then everyone is involved with the actual lab itself. [00:02:27]

[00:02:28] A reminder on your liquids. You have two liquids; corn syrup, corn starch. Don’t forget to shake, shake, shake. Shake, shake, shake. [00:02:39]

[00:02:40] Shake your corn starch and your corn syrup. [00:02:42]

[00:02:43] All right make sure those are really—especially the corn starch, cause that settles down at the bottom of the bottle. [00:02:47]

[00:02:47] The nice thing with this is, it’s all—the way I have it structured, everybody is busy all the time. [00:02:53]

[00:02:53] Remember on our hypotheses, it’s not a discussion time. It’s strictly just giving your educated opinion. [00:03:01]

[00:03:05] All right, you’re going to place three drops of each liquid in the trays. After you’ve done that, going one liquid at a time, you’re going to place one drop of iodine, mix it with your toothpick, observe. Everybody moves back to the scribe. Record your observations, record your results. [00:03:31]

[00:03:31] The aha moments are that first time they see the reaction with the iodine. It’s totally unexpected, and it’s so quick. [00:03:41]

Child: [00:03:47] Oh look. Whoa. [00:03:51]

Child: [00:03:51] So black. [00:03:52]

Child: [00:03:53] Okay it’s a bit darker than the water, but it’s not like super black. [00:03:58]

Child: [00:03:58] I’m surprised that [inaudible 03:59]didn’t have the same color as water because the same—they’re both water, so I thought they would both have the same color. [00:04:08]

Child: [00:04:11] Whoa, it’s turning tiny. [00:04:12]

Orsulak: [00:04:12] Yes a couple of people said it kind of reminded them of an egg. Like the yolk of the egg, and then the white. [00:04:18]

Child: [00:04:18] Yeah. [00:04:18]

Orsulak: [00:04:19] Yeah good observation. Good, great. [00:04:20]

[00:04:21] If you’d like to try this lesson, I’m going to provide for you, through the Teaching Channel, my lesson plan, my records sheets and that assessment tool and you can try it out and see if it works for you. [00:04:33]