Cleaning Copper: Apparatus
Cleaning Copper: Method
- Pour the vinegar into the bowl. Vinegar is a weak acid, so it may sting if it gets into your eyes or on your skin. If you or your child gets splashed wash it off immediately with cold water.
- Instruct your child to add the salt to the vinegar and stir until the salt dissolves. Discuss what is happening to the salt. (The salt is dissolving in the vinegar and a solution is being formed.)
- Ask your child to draw a picture of the pennies or write in their lab notebook a description of what they look like. Dull? Dirty?
- Have your child use the spoon to place the pennies into the bowl while counting out loud as each penny is placed into the bowl. The pennies should not be stacked on top of each other. Instruct your child to record the time in their lab notebook.
- Look at the pennies and ask your child to make observations about what is happening. After 5 minutes remove the pennies.
- Wash 4 pennies thoroughly under water, and put them on a paper towel to dry. Label the paper towel “W” for washed.
- Place the 4 unwashed pennies on a second paper towel and label this towel “NW”, for not washed. Record the time.
- After one hour, look at the pennies on the paper towels.
- Have your child record their observations in their lab notebook.
Questions to ask your child:
Notice anything different between the two groups of pennies?
What happened to the pennies that were washed, not washed?
Why did the pennies look dirty to begin with?
Results and Conclusions:
Chemistry is used to make dirty things clean and you have just seen a chemical reaction remove the dirt from an object. When you put your dirty pennies in the vinegar and salt, the copper oxide dissolved and the pennies became clean.Vinegar is a weak acid and copper oxide dissolves easily in a mixture of a weak acid and salt.
Matter otherwise known as “Everything around you” is made up of tiny particles called atoms and a penny contains copper atoms. Sometimes different atoms join together to make molecules. When the copper atoms in the pennies combine with oxygen atoms from the air they form a molecule called copper oxide. When the pennies are coated with copper oxide they looked dull and dirty.
Why did the unwashed pennies turn blue-green?
When the vinegar-salt solution dissolves the copper-oxide layer on the penny, then the copper atoms on the pennies that were not washed can join easily with oxygen atoms from the air and chlorine atoms from the salt to make the blue-green compound (known as malachite) you now see on the pennies.
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