Could you determine the amount of atoms in a substance?

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# Could you determine the amount of atoms in a substance? - PowerPoint PPT Presentation

Could you determine the amount of atoms in a substance? How do scientists count when atoms and molecules are so small?. Using the concept of counting by weight Could you determine the amount of atoms in a piece of copper?. What information would you need?.

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Could you determine the amount of atoms in a substance?

How do scientists count when atoms and molecules are so small?

### What information would you need?

The periodic table has a secret! It can tell you the amount of atoms in a specific mass of each element

Look at the amu of copper. The amu also describes the number of atoms in a specific mass in g
• Ex: There are 6.02 X10 23 atoms/63.546 g of copper
• Could you determine the amount of atoms in any piece of Copper?
6.02 X10 23 is a huge number!!!
• It is a unit of measurement that scientists use. Just as chefs use the dozen (12)
• This is manageable because atoms are so tiny
• They call this number a mole!! (sometimes abbreviated mol)
• With this new information could you determine the amount of moles if I gave you a specific mass of an element?
• Write a conversion you could use.
• Ex If I have .500g Al 1mol/26.98g How many mols do I have try it…
• .500g Al 1 mol/26.98g = .0185 mols of Al
If I gave you the amount of mols could you give me the mass?
• .496 mols of Al 26.98g Al/1 mol = 13.4 g Al
• If I gave you the number of atoms could you determine the mass?
• Remember there are 6.02 X10 23 atoms in a mol and the molar mass is the mass of one mole
• Find the mass of 2.03 X10 23 atoms of S
• 2.03 X10 23 atoms S 1 mol/6.02 X 10 23 atoms S 32.055g S/1 mol
• Answer = 10.8 g S

The number on the periodic table is called the MOLAR MASS. This gives you the mass in one mole of a substance.

Find the molar mass of O,S,N,F

Find the molar mass of H2O, HF

Can you find the mass of a particular amount of atoms?

Find the mass of 2.03 X10 23 atoms of S

2.03 X10 23 atoms S 1 mol/6.02 X 10 23 atoms S 32.055g S/1 mol