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Hi, Everyone!
My name's Hailee Talbot and I'm the STEM Education Student Assistant at University of Iowa Health Care.
Something that scientists (that's you!) use every day is the scientific method.
You may not know what that is yet, or even realize that you've used it before.
But, the scientific method is a series of steps that help you make observations and answer questions.
We're going to learn about the scientific method today by walking through each of the steps together
and doing an elephant toothpaste experiment.
First step in the scientific method, is making an observation.
You probably know hydrogen peroxide as an antiseptic used to kill bacteria in cuts or scrapes.
This is a liquid with the chemical formula H202.
When it breaks down,
it very slowly turns into water, H20
and oxygen, 02.
This leads us to step two,
ask a question.
We know this reaction happens very slowly.
Can we change the speed of the reaction?
What happens if we try to speed it up?
Is it even possible to change the speed?
Now, we're going to have to do some background research
to help answer our questions.
It looks like if we use a catalyst,
like yeast or sodium iodide,
we should be able to speed up the reaction process.
A catalyst is a substance used by a scientist
to speed up reactions
that would otherise be very, very slow.
The next step is to form a hypothesis, or an educated guess
based on information we know.
I'm going to hypothesize that if we add a yeast catalyst to hydrogen peroxide,
the hydrogen peroxide will break down faster than if we didn't use a catalyst.
Now, we can design an experiment to test our hypothesis.
We're going to add yeast to hydrogen peroxide
with a little bit of dish soap.
When hydrogen peroxide breaks down,
the oxygen gas usually escapes as bubbles that pop quickly,
so we wouldn't be able to see that.
By adding dish soap,
there is some surface tension that traps the bubbles and creates foam.
The supplies you'll need for this experiment are:
dish soap,
warm water,
dry yeast,
measuring cups,
bottles of various sizes,
food coloring, if you'd like to change the color of your elephant toothpaste,
and 3% hydrogen peroxide.
Be sure to use extra safety precautions if you're using a higher percentage.
Be sure to also set down a tray or mats to protect from any spills.
And, of course, safety first!
We're going to start by adding a half cup of hydrogen peroxide to our bottle.
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Next, we're going to add the dish soap.
You don't really need to measure this,
just give the bottle a good squeeze.
And then swirl around to mix with the hydrogen peroxide.
If you decided to add food coloring to your elephant toothpaste to change its color,
add that in now.
And make sure you swirl that as well.
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Now, we're going to add our catalyst,
which is yeast.
Mix 1 tablespoon of yeast with 3 tablespoons of warm water in a separate container
before adding it to your hydrogen peroxide mixture.
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You'll stir this mixture for about 30 seconds, until everything is mixed together.
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The last step, is pouring the yeast into the hydrogen peroxide
to catalyze the reaction.
After you pour it, take a step back and watch what happens.
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The reaction did not happen as I expected it to.
But, that's okay,
and it happens all the time in science.
Since this did not go as planned,
we must troubleshoot our procedure
and double-check all the steps and setup for the experiment.
It turns out that I used a teaspoon measurement for the yeast
rather than a tablespoon.
So, there wasn't nearly as much catalyst added as I thought.
This explains the slow reaction we saw.
The reaction is still happening much faster than it would without a catalyst.
And remember, it may be called 'elephant toothpaste'
but it's not actually toothpaste, so please don't try it.
Sometimes in the experiment step of the scientific method,
we have to try it a few times before we move on.
I'm going to try the experiment again,
but with the correct amount of yeast and a smaller  bottle.
I also tried to make my elephant toothpaste have stripes this time
by putting food coloring around the edge.
It's supposed to drip into the bottle to make the stripes,
but it didn't exactly work out for me.
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Alright.
Take two.
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This reaction was much closer to what I expected,
so I would call this one a success!
Now, we'll decide whether to accept or reject our hypothesis.
Since we didn't complete a control experiment,
where we see how long the reaction would take without a catalyst,
we can't truly accept our hypothesis yet.
But for this video, we knew from background information that the reaction was very slow.
So we can conclude that we have support for our hypothesis.
The yeast as a catalyst did help speed up the reaction process.
Next, we'll draw conclusions from our work.
Based on the results from our research and experiment,
we can conclude that yeast as a catalyst, does indeed, help speed up the breakdown
of hydrogen peroxide into water and oxygen gas.
Now that we've learned most of the scientific method,
and we've completed our experiment,
it's time for the final step,
sharing our results.
Typically, a scientist would share their results by publishing an article in a journal or
maybe sharing with a bunch of other scientists at a conference.
You can share your work by telling your friends and family about what you learned during this experiment
or maybe writing a lab report about it.
Whatever you decide to do,
stay curious.
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