Up to now, we’ve been looking at how matter reacts and changes on a large scale. Now, we’re going to examine why matter changes. To do this, we need to break matter down into its smallest units to understand how it works.
THE PARTICLE MODEL
All matter can be broken down into smaller pieces until you can’t break it down any smaller. The smallest particle that makes up any piece of matter is called a “building block.” Picture one Lego piece as a building block and a Lego castle as a large piece of matter. We can break the castle apart into smaller pieces: the individual Lego bricks, which represent building blocks. Building blocks of matter are called “atoms.” The particle model of matter is comprised of four main ideas:
- All matter is made up of tiny particles. Everything around you can be broken down into smaller particles called atoms.
- The particles of one substance are all the same and different substances are made up of different particles. For example, a glass of pure water is made up of only water molecules. All the molecules join together to create a large amount of water. A teaspoon of salt, on the other hand, is all made up of very small salt molecules
- Particles are always moving. If the particles have more energy, they will move faster. Heating causes particles to move faster because heating provides more energy to the particles. Particles in solids move very slowly, particles in liquids move fairly fast, and particles in gases move extremely fast.
- Particles are chemically attracted to each other. This force becomes stronger when the particles are closer together.
Understanding that all matter is made up of particles allows us to understand what happens in physical and chemical reactions. For example, when we add heat to ice, it starts to melt into water. This is because the heat is providing more energy to the water particles in the ice and they start to move faster. Once they move fast enough, the ice starts to break up and form liquid water.
PURE SUBSTANCES, MIXTURES, AND THE PARTICLE MODEL
All matter can be classified into two main categories: Pure Substances and Mixtures. Mixtures contain many different types of particles. There are many examples of mixtures, such as:
- Milk – milk is a combination of water, fats, proteins, vitamins, and minerals
- Potato Chips – These are a mix of potatoes, salt, oils, and preservatives.
As you may have noticed, mixtures can be separated into different substances. When we separate mixtures, we end up with pure substances. Pure substances are chemicals that cannot be broken down into smaller molecules. For example, we can take milk (a mixture) and separate all the parts into the water, fat molecules, protein molecules, and vitamin molecules (all pure substances that can’t be broken down into smaller particles without being those individual substances).
ELEMENTS, COMPOUNDS, AND THE PARTICLE MODEL
Scientists were further able to classify pure substances into two groups: elements and compounds. Elements are very small pure substances and include particles such as carbon, lead, gold, and over 100 others. Each element is a specific kind of atom and will be discussed further in a couple of days. Compounds are small molecules made up of two or more atoms in a fixed ratio, for example, water (H2O), salt (NaCl), and carbon dioxide (CO2).