Name ______Per. _____

Penny Alloy Lab

I. Problem: How can you model a physical change with pennies using chemistry? Can you change the amounts of the metals contained in a penny and change its properties, too?

II. Background information.

What is an alloy?

III. Materials:

Name ______Per. _____

Penny (new or cleaned in vinegar)

2 beakers

Hot plate

Evaporating dish

Zinc powder

2 M NaOH Hazard: Caustic, causes severe burns!

Paper towel

Forceps

Name ______Per. _____

IV. Procedures:

  1. Put on safety goggles and lab coat.
  1. Pug in the hot plate to heat the mixture of NaOH and zinc that is aleady in an evaporating dish on the hot plate. **DO NOT ALLOW THE SOLUTION TO BOIL VIGOROUSLY, DRY UP, AND DO NOT INHALE THE VAPORS!!!
  1. Using your forceps, carefully place a penny in the hot zinc/ sodium hydroxide solution. Do not drop the pennies in!!
  1. Stir the penny gently and carefully every few minutes and record your observations in the data table provided. Continue to boil the pennies until you observe no further changes.
  1. Turn off the burner and fill one beaker about one-quarter full of tap water.
  1. Remove the penny from the solution using your forceps and gently place itin the beaker. This is to cool the pennies and also to remove traces of the sodium hydroxide solution.
  1. Using your forceps remove the pennies from the beakers, place on a paper towel, and gently dry them off. Gently wipe off any zinc that has stuck to your penny with a paper towel.
  1. Unplug your hot plate, but leave the evaporating dish with zinc and NaOH in place.
  1. Using your forceps, transferthe dry penny from the paper towel to the heating element in the safety hood. Use the forceps to hold the penny on the edge.
  1. As soon as you see a change, remove the penny from the hot plate and place into the empty beaker of water. Remove with forceps and dry off. YOU HAVE CREATED AN ALLOY!
  1. Wash your hands thoroughly and clean up your station well. Return all equipment to the proper drawers.
  1. Answer the questions on the sheet provided underneath your data table:

Observations
Penny before heating
Penny after NaOH solution
Penny after hot plate

Conclusions:

  1. What two metals do the treated pennies remind you of?
  1. If someone showed you the gold penny and told you it was really gold, how would you decide if it was really gold?
  1. Name one use in everyday life for the alloy you made in this lab:
  1. What happened to the copper atoms on the outside of the treated pennies?
  1. List at least 2 advantages of using an alloy rather than a pure metal:
  1. Is this a physical change or a chemical change? Explain your reasoning:
  1. Explain at least 2 ways in which you could get the treated pennies to look like the original ones.