Mole (unit) facts for kids
Quick facts for kids Mole |
|
|---|---|
| Unit system | SI base unit |
| Unit of | Amount of substance |
| Symbol | mol |
A mole is a special unit of measurement used in science. It helps scientists count a very large number of tiny things, like atoms or molecules. Think of it like a "dozen," which means 12. A mole means a specific, much bigger number!
One mole of anything is equal to about 602,214,078,000,000,000,000,000 of those things. This huge number is called Avogadro's number. For example, if you had one mole of grapes, you would have 602,214,078,000,000,000,000,000 grapes! That's so many grapes, they would be bigger than the Earth!
Scientists use this number because it's the exact number of carbon atoms in 12 grams of a common type of carbon called carbon-12. Even though the number is huge, it's very useful for working with tiny atoms and molecules.
Because different atoms and molecules have different masses (how much they weigh), one mole of one substance won't weigh the same as one mole of another. For example, one mole of water molecules weighs less than one mole of sugar molecules.
Contents
Understanding the Mole
Imagine you have two bags of balls. One bag has 3 tennis balls, and the other has 3 footballs. Both bags have the same number of balls (3), but the bag of footballs weighs a lot more.
The mole works in a similar way. It measures the number of tiny particles, not their weight. So, if you have one mole of hydrogen atoms and one mole of oxygen atoms, you have the same number of atoms, even though the oxygen atoms weigh more.
Scientists use moles because atoms and molecules are too small to count individually. Also, their weights are very different. Using moles helps them compare amounts of different substances easily in chemical reactions. It's like having a special "counting unit" for the super small world of chemistry.
Using Moles in Math
Moles are very helpful for calculations in chemistry. Here are some simple ways they are used:
Finding Moles from Mass
You can find out how many moles of a substance you have if you know its mass and its "relative mass" (how much one mole of it weighs).
- Formula: Moles = Mass (in grams) / Relative Mass (in grams per mole)
Example: How many moles are in 20 grams of hydrogen? Hydrogen's relative mass is about 1 gram per mole. Moles = 20 grams / 1 gram/mole = 20 moles.
Finding Moles from Concentration and Volume
You can also find moles if you know how concentrated a liquid solution is and its volume.
- Formula: Moles = Concentration (in mol/dm3) x Volume (in dm3)
Example: How many moles are in 100 cm3 of 0.1M H2SO4 (sulfuric acid)? First, change 100 cm3 into dm3. (1 dm3 = 1000 cm3). 100 cm3 / 1000 = 0.1 dm3. Moles = 0.1 dm3 x 0.1 mol/dm3 = 0.01 moles.
Mole Mass of Molecules
To find the mass of one mole of a molecule, you add up the masses of all the atoms in it.
Example: A methane molecule (CH4) has one carbon atom and four hydrogen atoms.
- Carbon's mass is about 12.011 units.
- Hydrogen's mass is about 1.008 units.
So, the mass of one methane molecule is 12.011 + (4 × 1.008) = 16.043 units. This means one mole of methane weighs 16.043 grams.
Other Ways Moles Are Used
The SI unit for how much of a substance is dissolved in a liquid (called molar concentration) is mol/m3. However, chemists often use mol/dm3, which is the same as mol/L. These units are sometimes written as a capital letter M (pronounced "molar"). For example, "millimolar" (mM) means millimoles per litre.
When scientists talk about how much product they get from a chemical reaction, they often state it in moles. This is called the "molar yield."
Images for kids
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Avogadro, who inspired the Avogadro constant
See also
In Spanish: Mol para niños
