AS-Level Amounts of Substance

  • Atoms and particles are very small, so referring to actual numbers of atoms in a sample would require very large numbers that would be hard to work with.

  • The mole is just a unit used to refer to the amount of atoms or particles in a substance.

  • Just like one dozen = 12 of something, one mole = 6.022x10  of something.

  • The number one mole refers to is known as Avogadro’s constant.

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QUICK NOTES

The Mole

 

In all walks of life (not just A-level chemistry!) it is important to know how much of something you have. Whether it’s how much money you have in your wallet or how many litres of fuel you need to put in your car, it’s vital to know how much of a given thing you have. In chemistry there are two real ways of measuring how much of something we have –mass and volume.

 

Atoms are very small. This means, even for a small sample, a substance will have a lot of atoms in it. So many in fact, it’s not realistically possible to refer to the whole number of atoms or particles in the sample. Instead, we use a unit called ‘the mole’. Always remember – a mole is just a simple way of saying how many particles of something you have.

 

Just like 1 dozen = 12 of something; 1 mole = 6.02x10  of something.

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If you have two dozen atoms, you know that you have twenty-four atoms (2 x 12 = 24).  If you have two moles worth of atoms in a sample, it simply means you have 1.25x10  atoms that sample (2 x 6.02x10  ).

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Again - always remember – a mole is just a simple way of saying how many particles of something you have!