An element is matter than cannot be separated into different types of matter by ordinary chemical methods.

The liver produces bile which emulsifies (separates) fat.

A neutron is a subatomic particle found in the nucleus of an atom. It is neutral as it carries no electric charge.

Food is mixed with gastric acid and pepsin in the stomach to help break down protein.

The Earth's rocks fall into three categories based on how they're formed. Igneous rock (granite, basalt, obsidian) is formed from the hardening of molten rock (lava), sedimentary rock (shale, sandstone, coal) is formed by the gradual despositing and cementing of rock and other debris, and metamorphic rock (marble, slate, quartzite) which is formed when existing rock is altered though pressure, temperature, or chemical processes.