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Course: High school chemistry > Unit 4
Lesson 1: Moles and molar massThe mole and Avogadro's number
Google ClassroomOne mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10²³ is known as Avogadro's number or Avogadro's constant. The concept of the mole can be used to convert between mass and number of particles. Created by Sal Khan.
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Why scientific notation is important?(3 votes)
Scientific notation is used to represent huge numbers in a concise and easy way. With huge magnitudes involved in many science problems (like the mole), it would become very tiresome to write out so many numbers.
For instance 1 mole in in standard form would look like this:
602,600,000,000,000,000,000,000
Compared to scientific notation:
6.026x10^23
So much easier to write!(11 votes)
Why is scientific notation important?(2 votes)
I think someone already answered to the same question a few months ago, but basically, it's important because it's much easier to write than the standard form with all the zeros.(2 votes)
- Why scientific notation is important?(1 vote)
Scientific notation is important for several reasons, particularly in scientific, engineering, and mathematical contexts:
1. *Simplifies Large and Small Numbers*: It allows for the concise representation of very large or very small numbers, making them easier to read, write, and comprehend. For example, instead of writing 0.000000000056, you can write \( 5.6 \times 10^{-11} \).
2. *Reduces Errors*: When dealing with extremely large or small numbers, it's easy to miscount the number of zeros. Scientific notation reduces this risk by using powers of ten, which are easier to manage.
3. *Facilitates Calculation*: It simplifies multiplication and division of large or small numbers by allowing you to add or subtract exponents instead of dealing with numerous zeros. For example, \( (3 \times 10^5) \times (2 \times 10^3) = 6 \times 10^8 \).
4. *Standardization*: Scientific notation provides a standardized way of expressing numbers, which is particularly useful in international scientific communication and publications. It ensures consistency and clarity across different languages and regions.
5. *Precision and Significant Figures*: It helps in maintaining significant figures, which reflect the precision of measurements. This is crucial in scientific experiments where the accuracy of numbers is important. For instance, \( 3.00 \times 10^2 \) implies three significant figures, while \( 3 \times 10^2 \) implies one.
6. *Efficiency in Data Storage*: In computational contexts, scientific notation can save space and improve the efficiency of data storage and processing, particularly when dealing with large datasets or numerical simulations.
7. *Ease of Comparison*: It makes it easier to compare and understand the magnitudes of different numbers. For instance, it is immediately clear that \( 10^6 \) is much larger than \( 10^3 \), whereas comparing 1,000,000 and 1,000 might not be as immediately intuitive.
8. *Real-world Applications*: It is essential in various scientific disciplines like astronomy, physics, chemistry, and engineering, where numbers can span many orders of magnitude. For example, the distance between stars (in light-years) and the size of atoms (in meters) are conveniently expressed in scientific notation.
In summary, scientific notation is a powerful tool for efficiently and accurately handling and communicating numerical information in many fields of study and industry.
Hope this helps(1 vote)
- So 1 mole = the Avogadro number, right?(1 vote)
- What does moles into Avogadro number give?(0 votes)
Video transcript
- [Narrator] In a previous video, we introduced ourselves to the
idea of average atomic mass, which we began to realize
could be a very useful way of thinking about a
mass at an atomic level or at a molecular level. But what we're gonna do in this video is connect it to the masses
that we might actually see in a chemistry lab. You're very unlikely to just be dealing with one atom or just a few
atoms or just a few molecules. You're more likely to
deal with several grams of an actual substance. So how do we go from the
masses at an atomic scale to the masses of samples that you see in an actual chemistry lab or in, I guess, you could
say our scale of the world? Well, the chemistry community has come up with a useful tool. They've said, "All right, let's think
about a given element." So say lithium, we know it's
average atomic mass is 6.94. 6.94 unified atomic mass units per atom, atom of lithium. What if there were a certain
number of atoms of lithium such that if I have that number, so times certain number of atoms, then I will actually end up
with 6.94 grams of lithium and this number of atoms is 6.02214076 times 10 to the 23rd power. So if you have a sample with
this number of lithium atoms, that sample is going to
have a mass of 6.94 grams, whatever its average atomic masses in terms of unified atomic mass units, if you have that number of the atom, you will have a mass of that
same number in terms of grams. Now, you might be saying, "Is
there a name for this number?" And there is indeed a name and it is called Avogadro's Number, named in honor of the early
19th century Italian chemist, Amedeo Avogadro and in most contexts, because you're not
normally dealing with data with this many significant digits, we will usually approximate it as 6.022 times 10 to the 23rd power. Now, there's another word
that it's very useful to familiarize yourself with in chemistry and that's the idea of a mole. Now, what is a mole? It is not a little mark on your cheek, it is not a burrowing animal, actually, it is both of those things. But in a chemistry context, a mole is just saying you
have this much of something. The word mole was first
used by the German chemist, Wilhelm Oswald, at the
end of the 19th century and he came up with the word because of its relation to molecule. Now, what does that mean? Well, think about the word dozen. If I say I've got a dozen of
eggs, how many eggs do I have? Well, if I have a dozen of
eggs, that means I have 12 eggs. So if I say I have a
mole of lithium atoms, how many lithium atoms do I have? That means that I have 6.02214076 times 10 to the 23rd lithium atoms. Exact same idea. It's just that Avagadro's
Number is a much hairier of a number than a dozen.