Materials

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.

The gases around you every day, inside or outside, is called the air. You need to breathe air to stay alive.

An alloy is a mixture of two or more metals, or one metal and something that isn't a metal. They are mixed together so well you cannot tell that the alloy is not a pure metal. Alloys typically have very different properties to the components that went into making the alloys. Alloys are often much, much stronger than their individual components. Many tools and machines are made from alloys because they need to be strong.

Aluminium, also spelt aluminum, is the most common metal in the world, and the third most common element (after oxygen and silicon). It is durable and lightweight, and is a very important metal for making planes out of.
Aluminium is highly reactive and you cannot find pure aluminium in the same way you can find pure gold or copper, so it was once considered a rare precious metal. It is a very energy intensive process to refine aluminium.
Aluminium is used for building (particularly frames for doors and windows) and vehicle construction, household aluminium foil, masts on ships, walking sticks, and lots of household utensils and appliances.

Amethyst is a violet variety of quartz, with the purple colour coming from trace amounts of iron and aluminium. Amethyst is a popular stone for making jewelry from.

Asbestos refers to a group of silicate rocks that have the interesting property of forming long, thin fibers. Asbestos was cheap, strong, had great insulating qualities and was widely used as a building material, with its use peaking in the 1970s.
Asbestos can cause lung cancer, mesothelioma and other issues if it is inhaled, and because of this its use is currently banned in many countries.

Aventurine is a type of quartz which has impurities that make it green, translucent, and with a shimmering effect. Some types of aventurine are orange, brown, yellow, blue, or grey but the most common is green. Most of the world's green aventurine is found in India.

Basalt is a common rock made by lava cooling down quickly. Basalt is usually dark grey or black. Depending on how it cools down, basalt can be found in columns like in the picture, in a grid or hexagonal pattern, or even full of bubbles.

Beryl is a colorless mineral made up of beryllium aluminium cyclosilicate. It forms hexagonal crystals that can be very large. When beryl has impurities, it can have a coloured tint or be opaque. Coloured beryl has different names - green beryl is called emerald, pale blue beryl is called aquamarine and pink beryl is called morganite.

A block is a piece of wood, stone or another kind of masonry that is used to build things out of.
Blocks can be very big and used to make buildings from, or very small and used as a children's toy.
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.