Instructions 1. Take a chunk of chalk and measure its mass on the balance: __ 2. Go outside and draw something on the sidewalk. 3. Go back in class and weigh the unused chalk: __ 4. Based on the initial mass of the chalk and the mass at the end, calculate how many grams of chalk you left out on the sidewalk: __ 5. Write down the molecular formula of the chalk: __ 6. Get the masses of the atoms: 7. Calculate the chalk's molar mass: __ 8. Using this data, calculate: a. How many moles of chalk did you leave on the sidewalk? __ b. How many molecules of chalk did you leave on the sidewalk? __ c. How many atoms of calcium did you use? __ d. How many atoms of carbon did you use? __ e. How many atoms of oxygen did you use? __

## Step 1: Calculate mass of chalk left on the sidewalk### Subtract the final mass of the chalk from the initial mass. ## Step 2: Calculate the number of moles of chalk left on the sidewalk### Use the molar mass of chalk to convert the mass to moles. ## Step 3: Calculate the number of molecules of chalk left on the sidewalk### Use Avogadro's number to convert moles to molecules. ## Step 4: Calculate the number of atoms of calcium used### Since there is 1 calcium atom per molecule of , the number of calcium atoms equals the number of molecules. ## Step 5: Calculate the number of atoms of carbon used### Since there is 1 carbon atom per molecule of , the number of carbon atoms equals the number of molecules. ## Step 6: Calculate the number of atoms of oxygen used### Since there are 3 oxygen atoms per molecule of , multiply the number of molecules by 3.