1. Counting Atoms

2. What was the purpose of the lab we did yesterday?
List 2 things you observed happening.
Define the Law of Conservation of Mass.
Bellringer 10/25

3. How do we count atoms? Remember!
Subscripts are the little numbers that tell us how many atoms there are.
EX- H2O
Coefficients are regular sized numbers that tell us how many molecules there are.
EX- 3NO
How do we count atoms?

4. If there is a chemical compound with only subscripts then it’s whatever the subscripts tell you!
1 atom of Carbon
4 atoms of Hydrogen
If there are both subscripts and coefficients multiply all the subscripts by the coefficient
How do we count atoms?

5. How do we count atoms? Here are 5 easy steps
Write the chemical formula
List all the atoms
Count the number of atoms of each element in 1 molecule
Multiply the number of atoms of each by the coefficient
Make sure your answer makes sense
How do we count atoms? Here are 5 easy steps

6. 4C6H12O6 (glucose-sugar) C- 4 x 6= 24 H- 4 x 12= 48 O- 4 x 6= 24
What’s the total number of atoms in sugar?
= 96 atoms!
Practice

7. 6C2H5OH C- 2 x 6= 12 H- 5 x 6= 30 O- 1 x 6= 6 H- 1 x 6= 6 Practice
But wait… “H” appears twice! That’s okay, you want the TOTAL number of H… so that means there are 30+6= 36

8. 5 Ca(OH)2 Ca- 5 x 1= 5 O- 5 x 2= 10 H- 5 x 2= 10 More Practice 
How many total atoms are in calcium hydroxide?
There are 25 atoms total!
More Practice 