Matter is the Stuff Around You
Matter is everything around you. Matter is anything made of atoms and molecules. Matter is anything that has mass and takes up space. If you are new to the idea of mass, it is the amount of stuff in an object. We talk about the difference between mass and weight in another section. Matter is sometimes related to light and electromagnetic radiation. Even though matter can be found all over the Universe, you only find it in a few forms. As of 1995, scientists have identified five physical states of matter. Each of those states is sometimes called a phase. They may even discover one more state by the time you get old.
Five States of Matter
You should know about solids, liquids, gases, plasmas, and one state called the Bose-Einstein condensate (BEC). Scientists have always known about solids, liquids, and gases. Plasma was a new idea when it was noticed by William Crookes in 1879. The scientists who worked with the Bose-Einstein condensate received a Nobel Prize for their work in 1995. But what makes a state of matter? It's about the physical state of the molecules and atoms. Think about solids. They are often hard and brittle. Liquids are all fluidy at room temperature. Gases are there, but you usually smell them before you can see them. You don't see them because their molecules are really far apart. The BEC is all about molecules that are really close to each other (even closer than atoms in a solid).
Changing States of Matter
Elements and compounds can move from one physical state to another and not change their basic atomic parts. Oxygen (O2) as a gas still has the same properties as liquid oxygen. The liquid state is colder and denser, but the molecules (the basic parts) are still the same. Water (H2O) is another example. A water molecule is made up of two hydrogen (H) atoms and one oxygen (O) atom. It has the same molecular structure whether it is a gas, liquid, or solid. Although its physical state may change, its chemical state remains the same.
So you're asking, "What is a chemical change?" Let's start with a glass of pure water. If the formula of water were to change, that would be a chemical change. If you could just add a second oxygen atom, you would have hydrogen peroxide (H2O2). The molecules in your glass would not be water anymore. A chemical change happens when the atoms in a molecule are moved around or when atoms are added or taken away. Chemical changes happen when bonds between atoms are created or destroyed. Changing physical states of matter is about changing densities, pressures, temperatures, and other physical properties. The basic chemical structure does not change when there is a physical change.
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