1.1 Scientific Method

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來自 Duke University 的課程

Introduction to Chemistry: Structures and Solutions

79 個評分

Duke University

Introduction to Chemistry: Structures and Solutions

79 個評分

This is an introductory course for students with limited background in chemistry; basic concepts such as atomic and molecular structure, solutions, phases of matter, and quantitative problem solving will be emphasized with the goal of preparing students for further study in chemistry.

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Review Videos (I)

<p>Welcome! Over the eight weeks of the Introduction to Chemistry: Structures and Solutions course, we will begin discussions about the electronic structure of the atom, structures of molecules, phases of matter, and solutions. This week, we included some basic concept videos in Chemistry. These come from the partner course called Introduction to Chemistry: Reactions and Ratios. You can technically start with either course, but when these courses were originally designed, the Reactions and Ratios content came first, and you might find it helpful to complete that course before this course. If you are not familiar with the concepts of physical change v.s. chemical change, or significant figure and scientific notations, then please begin by reviewing video “Introduction”. I hope you enjoy this week's materials!</p>

1.0 Introduction7:42

1.1 Scientific Method9:00

1.2 Measurement and Significant Figures Part I 16:26

1.3 Measurement and Significant Figures Part II 13:06

1.4 Energy Part I 14:49

1.5 Energy Part II 14:18

1.6 [DEMO] Physical Change 3:42

1.7 [DEMO] Chemical Change 4:11

與講師見面

Prof. Dorian A. Canelas
Assistant Professor of the Practice
Chemistry

Hello and welcome back to introduction to Chemistry.

In the last lecture we talked about Dalton's atomic theory,

but you might be asking yourself, what exactly is a theory?

And what proces did Dalton use to arrive at his theory about atoms and molecules?

It might surprise you to find out that

you've been using the same process Dalton used to

come up with his atomic theory all the time.

That process is called scientific reasoning.

Sometimes the process is summarized in something called the scientific

method, which is often actually considered a collection of methods.

But let's look at an example of the scientific method.

Every day throughout your life, you are making a whole bunch of observations.

In fact, let's talk about some observations

you made when you were an infant.

Because you've been doing this process for your entire life.

At some point, whoever feed you got tired of spitting

food in your mouth and they handed you eating utensil.

Probably, it was a spoon.

You made lots of observations about that spoon: what

it tasted like what it sounded, like when you

whacked it on a surface, how you could scoop food with it.

At some point, you've probably accidentally dropped it, because

you weren't very coordinated, and you made an observation that

someone came and got it for you, and gave

it back to you, because you were well cared for.

After a while, after accidentally dropping it a few times, you

might have come up with an idea in your little baby brain.

And that idea may have been,

that person keeps bringing me back my spoon.

I bet if I drop the spoon again, the person will bring me the spoon.

In other words, you may have come up with the idea that the

reason why that person was there was to bring you your spoon back.

Eventually, like all infants, after you

had developed this hypothesis, that's the fancy

word for your idea, you predicted that the person would bring you the spoon.

And you decided to do an experiment.

And here's how that experiment went: you held your

hand up, you looked at the person who was supposed

to bring you the spoon, you drop the spoon

and you look down to see where the spoon went.

And then you looked back at the person

that who was supposed to bring you the spoon.

You did experiment to see will that person bring me the spoon again or not?

In other words, you made a new observation.

And that new observation about whether or not the person brought you the

spoon either supported or refuted your

hypothesis about why that person was there.

Now, if a hypothesis is supported by many,

many, many experiments done over a series of time

by a bunch of different people, then that hypothesis

becomes glorified by the more dignified name of theory.

Now, some people think, well, a theory is

just a guess, but that's not true in science.

In science, a theory is something that has been supported by many, many

experiments, and it hasn't been shown to be false by any of those experiments.

A theory must be falsifiable.

In other words, there might, at some point in the

future, be an experiment that shows the theory is not correct.

But most

scientific theories that you see published in books

have been supported by all of the experimental evidence.

Another thing that sometimes happens when people

do many, many experiments, is that they collect

some of the experimental observations into something

that they can make into a mathematical formula.

And that is usually called a law.

So, at this point you might be wondering okay sometimes I have a theory and

sometimes I have a law.

What's the difference between a theory and a law?

Well,

a theory applies to all events over a long

range of time and it explains why things happen.

A law, on the other hand, describes what happens, perhaps in the

form of an equation, but it doesn't try to explain why things happen.

That's what a theory does.

Now, sometimes, students are confused about what's

the difference between a hypothesis and a theory.

A hypothesis and a theory are both very similar, as you can see.

They both explain why something happens.

But a hypothesis is an explanation of why something

happened today, to me, to a small number of events.

Whereas a theory is an explanation of why something happens

that applies to all events over a large period of time.

The same can be true about the, said

about the relationship between an observation and a law.

An observation describes what happens in the moment where

a law describes what happens all of the time.

Let's apply what we've learned about the scientific method to these balloons.

The first thing I'd like you to do is make some observations about these balloons.

No observation is too obvious.

Go ahead and type whatever comes to your mind.

Great.

Now, the types of observations that

students usually make include things like: both

balloons are floating, both balloons are tied

to strings, the balloons are different colors.

Those are all perfectly good observations.

Sometimes, students, delve into the territory

of hypothesis when they're making their observations.

Now you made the observation

that the balloons were floating.

That meant that the substance inside of the balloon was less dense than the air.

So some of you said, I bet those balloons are filled with helium,

but you can't observe the helium, so that's a hypothesis, not an observation.

That's your guess about why the balloons are floating.

Others of you might have said, well, I think they're probably filled with helium.

But

I'm a history buff and I remember the Hindenburg.

The Hindenburg wasn't filled with helium.

It was filled with hydrogen.

It was a balloon that floated, but it wasn't filled with helium.

So there's a couple of gasses that I can think of

that might be causing those balloons to float, helium or hydrogen.

Well, we have some hypotheses now about what the balloons might be filled with.

What do you predict will happen if we pop

the balloons open?

Let's make a prediction about these balloons.

Do you predict that the balloons are filled with the same gas and

that the same thing will happen to both balloons when we pop them?

Or do you predict that the balloons are comprised of different gases?

That they're filled with different gases, and

different things will happen when we pop them?

Go ahead and record your answer.

Do you think they're filled with the same gas?

Or do you think they're filled with a different gas?

And which gas do you think is in these balloons?

Hydrogen or helium?

Okay, now. You've made your prediction.

Let's go ahead and do the experiment.

Let's use a candle to pop the balloons and see what happens.

Let's make some observations about what happens

when we pop the balloons with a candle.

Now this first balloon, here comes the candle,

it's going to hit the balloon, All right?

[SOUND] That was interesting. Now let's see if we can make

the same observation when we pop the second balloon.

Here comes the candle.

[SOUND]

Did your observations support or refute your

hypothesis about what was in those balloons?

Did you guess correctly?

If you did predict correctly, would you like to

say that your hypothesis is also a theory now?

In other words, for balloons that float,

must they be filled with hydrogen or helium

or do you think that your prediction only

applied to that one particular set of balloons?

Again, if the observations can be collected into an equation,

like a mathematical equation, then we would call that a law.

I hope you've had fun today using the scientific method.

[MUSIC]

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