The document discusses the concept of a dozen and introduces Avogadro's number as a more appropriate unit than a dozen for counting very small particles like atoms and molecules. It notes that a dozen equals 12 items or objects, while Avogadro's number (6.022 x 1023) is more suitable for microscopic entities since it represents the number of constituent particles in one mole of a substance. The document suggests replacing the term "dozen" with "mole" and 12 with Avogadro's number when calculating quantities of very small particles.

2. Just a number
Represents 12 items
Eggs Sugar crystals coins bulbs
Watermelons Salt particles spoons Test tubes
stones cows watches Sand particles
oranges Wheat grains dresses bags
grapes elephants aeroplanes stars
countries men houses chairs
atoms molecules ions electrons

3. 1 dozen = 12
therefore: n dozen = 12 n where n is a natural number
And
N items = N/12 dozen where N is the number of items.
Eg: 6 dozen eggs = 12 x 6 = 72 eggs
And
36 roses = 36/12 = 3 dozen roses

5. 1 dozen of each item = 12 but their
weights are different
Weight of 1 dozen watermelons = 30 kg wt
Weight of 1 watermelon = 30/12 = 2.5 kg wt
Therefore wt. of 1 item = M/ 12
M = wt. of 1 dozen

6. Atom is very small, smaller than our imagination.
For small particles like salt particles is it fine to talk of 1
dozen or is it a very small number?
Imagine 12 atoms/ molecules / electrons
Should we talk of 1 dozen of these microscopic entities ?
OR
choose a larger number?.

7. No = 6.022 x 1023 particles
Scientists came up with a number N
called Avogadro Number

8. 6.022
x
1023

9. 1 mole = atomic/ molecular mass in grams
Molar mass is mass of 1 mole
represented by M

10. • n dozen = 12 n where n is a natural number
• N particles = N/12 dozen where N is the number of particles
• wt. of 1 particle = M/ 12
Now replace
dozen by mole and 12 by No (= 6.022 x 1023)
• n mole = No x n where n is a natural number
• N particles = N/ No moles where N is the number of items.
• Wt. of 1 mole =M (molar mass) wt. of 1 particle = M/ No gm

11. Let us explore…..
10 moles of oxygen atoms = ………. Atoms
10 moles of oxygen O2 gas = ……….. Molecules
10 moles of oxygen gas = ………… atoms
12.044 x 1024 sodium ions = ………. Moles
6.022 x 1020 water molecules = ………. moles