Why did the vinegar and salt clean the pennies?
Copper oxide dissolves in a mixture of weak acid and table salt-and vinegar is an acid. You could also clean your pennies with salt and lemon juice or orange juice, because those juices are acids, too. Why did the unrinsed pennies turn blue-green? When the vinegar and salt dissolve the copper-oxide layer, they make it easier for the copper atoms to join oxygen from the air and chlorine from the salt to make a blue-green compound called malachite. How did the nail and the screw get coated with copper? To understand how the nail and screw got coated with copper, you need to understand a little bit more about atoms. Atoms are made up of even smaller particles called protons, neutrons, and electrons. Electrons and protons are both electrically charged particles. Electrons are negatively charged and protons are positively charged. Negative charges attract positive charges, so electrons attract protons. When you put your dirty pennies in the vinegar and salt, the copper oxide and some of the
