LAB: Size of a atom Purpose: To calculate the density of zinc. To use our calculated zinc density value to calculate the diameter of a zinc atom

Procedure: Part 1--Density of Zinc 1. Find the mass of several pieces of Zinc together. Record this mass in a data table. 2. Add an amount of water to a graduated cylinder sufficient to cover your pieces of zinc when they are added, but not so great that the level of water will rise above the top of the gradations when the zinc is added. Measure and record this amount of water in your data table. 3. Add the pieces of Zinc to the water and record the new volume of water/Zinc into your data table. 4. Repeat all measurements with a second sample of zinc pieces.

Post Lab Questions: Please show, explain and label all work and calculations. Answer question in complete sentences that incorporate the question.

Part 1 1. Using the values from your data table, show all work for finding the volume of zinc used in both trials. 2. Using the values from your data table, show all work for finding the density of zinc for both of your trials. 3. 3. Calculate an average density. Density = mass / volume 4. If the accepted density of zinc is 7.14 g / ml, find the percent error in your average value. % error = ((accepted-experimental)/accepted)*100 5. For each of the following possible errors, discuss what effect it would have had on your calculated density and explain why. a. If you measured the volume of the zinc pieces before you measured the mass. b. If the pieces of zinc metal trapped air bubbles inside them when you measured their volume.

Procedure: Part 2—Size of a zinc atom. 1. Measure the length and width of a piece of galvanized iron accurately and record the measurements in a data table. 2. Find the mass of the piece of galvanized iron and record it in your data table. 3. Place the square of galvanized iron into the bottom of a 150 mL beaker and place the beaker in the sink. 4. Carefully add enough 3 M Hydrochloric acid to completely cover the square. 5. Watch the reaction carefully. It should bubble rapidly when the acid is first added. As the Zinc is removed the bubbling should decrease and the exposed iron should start to discolor. At this point carefully turn the piece of zinc over using a pair of tweezers. Allow both sides to completely stop bubbling. This is when we want to stop the reaction. 6. To stop the reaction add about 300 mL of tap water to a 400 mL beaker. Carefully pour the acid and iron metal into the water. Carefully rinse the small beaker into the larger one. Then pour all of the liquid into the waste bucket at each table. 7. Remove the iron square with tongs and rinse thoroughly. Dry the iron square completely. Find the mass of the iron square and record it in your data table. 8. Clean up and return all supplies.

PART II 5. Show all work for finding the difference in the mass of the galvanized iron square before and after being soaked in acid. 6. Using your average calculated density of zinc from part I and the difference in mass from part II, show all work for finding the volume of zinc removed from the square. 7. Using the width and thickness of the piece of galvanized metal, and the volume of zinc removed to calculate the thickness of zinc removed.

8. That zinc removed was from both sides of the metal square. What was the thickness of the zinc removed from just one side of the metal?

9. According to the makers of the galvanized metal, they place approximately 120,000 layers of zinc atoms in that galvanized layer. Assuming that is true, calculate the diameter of a single zinc atom.

10. How small is that? Think of the smallest thing you can see (the width of a hair, or a single piece of dust or ???). Do some research and try to find out the size of that smallest thing you can see. Calculate how many times smaller than that object the zinc atom is.

11. Scientist who have very carefully done labs similar to this one have calculated the zinc atom to have a diameter of 2.68 x 10-8cm. Assuming that value to be correct, calculate your percent error. % error = ((accepted-experimental)/accepted)*100

12. Using the “correct” diameter given in question 11, calculate the volume of a single zinc atom if you assume that it is a perfect sphere.

13. Using the total volume removed and the volume of a single atom, calculate the total number of atoms removed.

14. Is this a lot? Think of something you think there a lot of (people in the world…gallons of water in the ocean…???) Do some research and try to find out how many there are of that thing. How many times more atoms were there on this iron?

15. For each of the following possible errors, discuss what effect it would have had on your calculated diameter of a zinc atom and explain why. a. If the metal was removed from the acid before all of the zinc was removed. b. If the metal remained in the acid too long and some of the iron was dissolved. c. If the metal was still wet when it was weighed in the end.