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This Experiment has (2) versions!
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Iodine Clock Reaction

Autopause

Materials

1 Bottle of Hydrogen Peroxide
1 Bottle of Hydrogen Peroxide
1 Bottle of Sodium Iodine
1 Bottle of Sodium Iodine
1 Bottle of Starch
1 Bottle of Starch
1 Bottle of Sodium Sulfite
1 Bottle of Sodium Sulfite
1 Measuring Cup
1 Measuring Cup
1 Petri Dish
1 Petri Dish
3 Plastic Cups
3 Plastic Cups

Instructions

STEP 1
0:00

Reach into your kit and pull out the bag with the four bottles in it. Take everything out of the bag and place it around the white mat. Then, place the empty bag back in your box.

STEP 2
0:22

These liquids are color-coded for easy matching. One has green on the edges of the label and the other has blue. Start by matching the colored bottles together. The two blue bottles go together and the two green bottles go together.

STEP 3
0:39

First, let’s mix the green bottles together. Carefully unscrew the tops and squeeze the liquid from the smaller green bottle into the bigger green bottle. Make sure the cap goes back on tight and give it a light shake to mix.

STEP 4
1:33

Next, we need to mix the blue bottles together. Carefully unscrew the tops and squeeze the liquid from the smaller blue bottle into the bigger blue bottle. Make sure the white cap goes back on tight and give it a 3-second shake to mix.

STEP 5
2:18

Next, gently twist to open the top of the green bottle so that you can easily squeeze out the liquid. Then, fill the measuring cup with 12.5ml.

STEP 6
3:17

Go ahead and pour the liquid from the measuring cup into the petri dish.

STEP 7
3:23

Next, let’s do the same thing with the other bottle. Gently twist to open the top of the blue bottle so that you can easily squeeze out the liquid. Then, fill the measuring cup with 12.5ml

STEP 8
3:35

Finally, go ahead and pour this liquid from the measuring cup into the petri dish slowly, and then watch… keep watching for something to happen.

STEP 9
3:41

It turned blue! And each time we do this reaction, it makes a different pattern when changing. Let’s do it again.

STEP 10
4:03

Pour the blue liquid from your petri dish into one of the empty cups provided and repeat the steps above to watch this reaction make a new pattern.

STEP 11
5:15

Now, clear your workspace and place the two empty cups in the center. Let’s see what happens when we do this same experiment in cups.

STEP 12
5:26

Start by filling the measuring cup all the way up with the liquid from the green bottle. Then pour all the liquid in your measuring up into the large empty cup.

STEP 13
5:45

Repeat the same steps with the blue bottle. Fill the measuring cup all the way up with the liquid from the blue bottle. Then pour all the liquid in your measuring cup into the last large empty cup.

STEP 14
5:58

Mix the liquids together by pouring one cup into the other. Do this back-and-forth three times.

STEP 15
6:27

Now, let’s count down from 10 to see the reaction! 10… 9… 8… 7… 6… 5… 4… 3… 2… 1… Blue! That was like magic!

STEP 16
8:50

Finally, let’s try it again but this time with different amounts. This time, only fill ½ of the measuring cup with the liquid from the green bottle and pour it into one of the empty cups. Tip: it should be approx. 10ml

STEP 17
9:07

Next, fill the entire measuring cup with the liquid from the blue bottle and pour it into the other empty cup.

STEP 18
9:16

Now let’s mix them together three times and countdown from 10, just like before.

STEP 19
9:27

After mixing three times like before, do you notice changes in the timing? This time it happened much faster!

STEP 20
9:36

Now let’s try it once more. This time fill the entire measuring cup with the liquid from the green bottle and pour it into an empty cup.

STEP 21
9:58

Then, fill only half of the measuring cup with the liquid from the blue bottle and pour it into the other empty cup.

STEP 22
10:08

Now mix the cups together again three times and start the countdown from 10. Do you notice changes in the timing this time? This time it happened much slower!

How It Works

This experiment is another type of chemical reaction called a clock reaction. It’s called a clock reaction because you literally count to see how long it takes the color to change. This delay happened because there are two chemical reactions happening at the same time and they are competing with each other.

Two of the chemicals want to make it clear and the other two want to make it blue. They compete like a game of tug-of-war. At first, the clear team is winning, but it gets tired out and all used up, so eventually, the blue team wins. This means that the amount of chemicals we mix in can change how long the countdown takes.
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