Investigating Ions: Copper Topping

This activity is designed for students to be able

• To observe a chemical reaction and describe their observations.
• To observe and infer some properties of copper and iron.
• To make predictions of outcomes based on modifications and test same.
  

Key Concepts:

• To understand the difference between chemical and physical properties.
• To understand that materials can be broken down into parts too small for the naked eye to see.
• To understand that experiments can only have one variable at a time.
• To understand that each experiment needs a control.

Vocabulary:

• Plating - a thin metal coating
• Acid - a material with a pH of less than 7
• Dissolve - to mix a solid into a liquid until no more solid is visible
• Verdigris - a thin green coating that can appear on copper (pennies) over time.
• Ion - any atom that either has extra electrons or is missing some electrons.

Grade Level - upper elementary through middle school

Class Size - not a limiting factor, experiment can be done in small groups or individually depending on amount of supplies.

Institution type - school setting, either classroom or lab

Time - basic lab will take approximately 2 hours

Previously mastered skills/concepts - reading directions, basic understanding of the concept of properties and atoms, using liquid measurement instruments

Curriculum - I introduce the idea of matter, atoms, properties, and etc. early in the 6th grade year to provide a basis for the remaining curriculum.

Setting Adaptations - This experiment easily adapts to either classroom or lab setting as long as water is available, material gathering, and clean-up procedures are previously established.

Introduction: I would introduce this activity by discussing the concept of an atom, the Periodic Table, and physical and chemical properties. I would hold up a nail or paper clip (item to be plated) and ask students to describe its physical properties and have them discuss ways to change the nail both physically and chemically. I would use this discussion to lead into the lab activity that would begin with structured inquiry (plating the nail with copper) and then have students make predictions on the outcome of self-selected modifications (extensions) to the experiment. For my students, the majority of whom are ELL, I will introduce the vocabulary prior to starting the lab.

Materials:

1/4 cup vinegar (white)
1-teaspoon salt
2 (or more depending on number of extensions) plastic or paper cups
Plastic spoon or wooden stir stick
2 iron nails (not galvanized) or 2 metal paper clips
Watch or clock with second hand
Steel wool scoring pad
10 - 20 dull pennies
Goggles
String and tape

Directions:

1. Pour vinegar and salt into cup and stir until all salt dissolved.
2. Place pennies into vinegar/salt solution for five minutes.
3. While pennies are in solution, rub one of the nails or paper clip with the steel wool (to remove any finish) and set the other nail/paper clip aside as the control.
4. After the pennies have set in the solution for 5 minutes pour the liquid into a second cup and add one nail/paper clip to this liquid and allow to sit for one hour. Be sure to tie the nail/paper clip to a piece of string and suspend completely in the liquid. Otherwise any area the nail/paper clip has in contact with a solid it will not copper plate.
5. Observations should be made of the following before and after the experiment:

   Pennies
   Vinegar/Salt Solution
   Nail - control
   Nail - used in experiment

6. Students should rinse off and dry pennies.
7. After one hour students should pour off vinegar/salt solution, rinse and dry the nails/paper clips and make observations.
8. Students should discuss in either small or large group what has happened during the experiment and why. This can also be a written conclusion.

Extensions:
This activity can be extended in a number of ways:

• Clean vs. dull pennies
• Number of pennies
• Number of items to be plated at one time
• Type of liquid used - white vinegar, cider vinegar, lemon juice, orange juice, cola, etc.

In doing extensions students should review the concepts of variable and control and be able to identify each in their experiment. They should have a hypothesis and written conclusion for each extensions as well as an explanation for what did or didn't happen.

Activity from:
Fizz, Bubble, and Flash! Element Explorations & Atoms Adventures for Hands-On Science Fun! A Williamson Kids Can! Book, Anita Brandolini, Ph.D., Williamson Publishing Co., 2003,p. 89, http://homechemistry.blogspot.com/2008/01/penny-chemistry-verdigris-and-copper.html, and http://chemistry.about.com/cs/demonstrations/a/aa022204a.htm

"Why are the nails different colored? The copper from the plated pennies dissolves in the lemon juice (an acid), producing copper ions. When the iron nail is put into the acid, the copper ions are attracted to the iron and build up, layer upon layer, until the nail gets a new coat... Any atom that either has extra electrons o r is missing some electrons is called an ion." Fizz, Bubble, and Flash! Element Explorations & Atoms Adventures for Hands-On Science Fun!


"The copper that coats the nail (paper clip) comes form the pennies. However, it exists in the salt/vinegar solution as positively charged copper ions as opposed to neutral copper metal. Nails (and paper clips) are made of steel, an alloy primarily composed of iron. The salt/vinegar solution dissolves some of the iron and its oxides on the surface of the nail, leaving a negative charge on the surface of the nail. Opposite charges attract, but the copper ions are more strongly attracted to the nail than the iron ions, so a copper coating forms on the nail. At the same time, the reactions involving the hydrogen ions from the acid and the metal/oxides produce some hydrogen gas, which bubbles up from the site of the reaction - the surface of the nail (or paper clip)."
http://chemistry.about.com/cs/demonstrations/a/aa022204a.htm. 7/17/08


Possible issues or concerns:

• While vinegar is a household chemical I would strongly recommend the use of goggles.
  
• Students should be forewarned not to drink the vinegar/salt or any other solution.
  
• If the students do not rub their nail/paper clip long enough or well enough, the non-rubbed areas will not plate.
  
• Students should be cautioned that they need to follow directions carefully and that extensions should be carried out using only materials the teacher has provided.
  
• Depending on the students, teacher may want to approve any extension ideas before the students actually under take them.

Assessment can be either informal or formal depending on the students and their needs. Students could tell the teacher what has occurred, write a summary/conclusion, or complete a formal lab write-up.

5.I.B. 1-2

Controlled experiment

6.II.A. 1,2,7

Matter is made of small particles that explains the properties of matter

6.II.B 1-2

Differentiate between chemical and physical changes