List of materials.
Things that you can use to make other things from.
Acids are a type of chemical with certain properties. They react with metals and bases. Acids are found in all sorts of everyday things, and are not as dangerous as the industrial grade acids you sometimes see in movies. Many fruits contain acid. Oranges and lemons contain citric acid, which is shown being mixed with water in the picture.
Barbed wire, or barb wire, is a type of wire usually used for fencing that has twists of sharp wire along its length. Barbed wire is most often used on fences that keep livestock like cows and sheep from escaping. The sharp barbs on the wire will hurt anything that tries to climb over it.
A block is also a word used to describe a lot of small places that you live, like flats or apartments, that are joined together into one building.
Block is also used to describe something that stops something else from happening, like when you have writer's block you can't have any good ideas.