METAL CLEANER
Materials:
table salt
ketchup
small bowl
spoon
paper napkin
dirty pennies or other copper objects
Directions: Combine equal parts salt and ketchup in a bowl. Mix
together well with a spoon. Use a napkin to rub the dirty pennies
with the solution. The tarnish on the pennies will rub off
relatively easily.
Science:
Tarnish on metal is caused by a chemical reaction between the metal
and oxygen in the air. Metal can be cleaned through abrasion (which
can damage the metal underneath) or through a chemical reaction. In
this experiment, the salt is lightly abrasive, but a chemical
reaction is also occurring . When an acid (as is found in ketchup)
is combined with salt, Cl- ions form in solution. When applied to a
tarnished penny, these ions attack the oxides in the tarnish without
affecting the base metal, leaving a shiny finish.
Extensions: Try doing the same experiment but with soy sauce,
lemon juice or vinegar instead of ketchup. Which solution works
best?
NOTE: These
solutions may not be safe for all metals. |