Why does matter matter?

Matter is the "stuff" that makes up the universe. Everything around us, from the air we breathe to the chairs we sit on, is made of matter. In this study guide, we will explore what matter is, its states, and how it can change. We will also classify different types of substances and understand the basic structure of matter.

---

3️⃣ States of Matter

Matter is any physical object that has mass (weighs something) and takes up space (has volume). It can be found in three primary states: solid, liquid, and gas.

🧊 Solids

Here are some characteristics of a solid:

• Definite Shape and Volume: Solids have a fixed shape that does not conform to the container in which they are placed. Their volume is also fixed.
• Closely Packed Particles: The particles in a solid are tightly packed together in a regular pattern.
• Vibrational Movement: Particles in a solid vibrate about fixed positions but do not move from place to place significantly.

Based on these characteristics, the properties of solids include:

• High Density: Solids generally have higher densities than liquids and gases due to the close packing of their particles.
• Low Compressibility: Because their particles are already close together, solids cannot be easily compressed.

Think about an ice cube, which is just frozen water! It melts super quickly, but when it’s frozen, we cannot change its shape or volume. We also can’t compress it in the palm of our hands.

Image Courtesy of Live Science

💧 Liquids

Let’s discuss the characteristics of liquids:

• Indefinite Shape and Definite Volume: Liquids take the shape of the container they are in but maintain a constant volume.
• Less Closely Packed Particles than Solids: The particles in a liquid are close together but not in a fixed position, allowing them to slide past one another.

Now what about density and compressibility?

• Moderately High Density: Liquids have densities lower than solids but higher than gases. The density can vary with temperature and pressure.
• Slightly Compressible: Liquids are slightly more compressible than solids due to the greater distance between their particles.

So what if we take that ice cube from earlier and melt it down to water? It’ll take the shape of its container, but its volume is the exact same!

Image Courtesy of Live Science

⛽ Gases

Last but not least, some characteristics of gases include:

• Indefinite Shape and Volume: Gases expand to fill the entire volume of their container, adopting both its shape and volume. Think of gases as free within their space.
• Widely Spaced Particles: The particles in a gas are much further apart than in solids and liquids, leading to lower densities.
• Rapid and Random Movement: Gas particles move quickly in all directions, leading to the spreading out or diffusion of gases.

✌🏼 And their two properties:

• Low Density: Gases have much lower densities than solids and liquids due to the large distances between particles.
• Highly Compressible: Because of the large spaces between their particles, gases can be compressed much more than liquids or solids.

We can’t really visualize water vapor, but we know that gases, in general, float freely within the space they exist.

Image Courtesy of Live Science

---

🔄 Phase Changes

We’ve discussed three different states of matter, but how do objects transition between them?

Phase changes refer to the transitions between these three states, depending on if energy is being added or removed.

Here are the phase changes you should be familiar with:

1. Melting: solid to liquid (requires energy)
2. Freezing: liquid to solid (releases energy)
3. Condensation: gas to liquid (releases energy)
4. Vaporization: liquid to gas (requires energy), which includes boiling and evaporation
5. Sublimation: solid to gas without becoming a liquid first (requires energy)
6. Deposition: gas to solid without becoming a liquid first (releases energy)

Image Courtesy of Shmoop

Let’s focus on melting and why we require energy to melt an object or transition it from solid to liquid. Think about the ice cube example: how do we get ice to melt?

We hold it in the warmth of our hand! The heat energy in our palm gets transferred to the ice cube, giving it energy to melt into liquid water. That’s essentially what we mean when a phase change requires energy to occur.

The opposite is true for phase changes that release energy. Consider the process of making ice cubes: how do we turn water into ice?

We put it in the freezer! The cold environment of the freezer removes heat energy from the water, reducing the energy of the water molecules. As they lose energy, the molecules move less and start to arrange themselves into a fixed, structured pattern, turning the liquid water into solid ice.

---

🖇️ Physical vs Chemical Properties

Every substance has physical and chemical properties that we should be familiar with. We’ll delve deeper into this later in the course when we discuss bonding, but here’s a quick introduction.

📄 Physical Properties

Physical properties are characteristics that can be observed without changing the substance's chemical identity:

• Color
• Odor
• Density
• Melting point
• Boiling point

Experiment Idea: Measure various physical properties such as mass or boiling water to observe a physical change.

🔥 Chemical Properties

Chemical properties describe a substance's ability to undergo changes that transform it into different substances:

• Reactivity with other chemicals
• Flammability
• Oxidation state

Experiment Idea: Combining vinegar with baking soda demonstrates a chemical change where new substances form.

---

🤔 Categorizing Matter by Composition

So far, we discussed categorizing matter by its state: solid, liquid, or gas. We’ll now begin to categorize it by composition: what is it made of? What is the arrangement of its atoms?

Pure Substances

Pure substances consist of only one type of atom or molecule. They are characterized by having uniform and definite composition and can be further divided into:

1. 🪙 Elements: An element is a pure substance made up of only one kind of atom. Think about the periodic table of elements, some examples include carbon (C) and gold (Au)
2. 🌊 Compounds: A compound consists of two or more elements chemically bonded together in a fixed ratio. They will always be combined in that said ratio to create that specified compound. Since compounds are made up of several elements, they can be broken down by chemical reactions. Some examples are water (H₂O) and carbon dioxide (CO₂).

These pure substances are one division of matter. Mixtures are the next. 👇

Mixtures

Whereas pure substances have one type of atom or molecule, a mixture contains two or more substances physically combined but not chemically bonded. Since they are not chemically bonded, each substance retains its own chemical properties and identity.

Mixtures can be categorized based on their uniformity and the size of their particles into:

1. 💨 Homogeneous mixtures: These mixtures have a uniform composition throughout. Their components are evenly distributed and cannot be distinguished from one another.
   1. An example is atmospheric air made of gases such as N₂ and O₂. We can’t tell what is oxygen and nitrogen, so it is homogenous.
2. 🥗 Heterogeneous mixtures: These do not have a uniform composition. Their components are unevenly distributed and can typically be physically separated.
   1. An example is a salad, which is a mixture of lettuce, tomatoes, and other things, but we can easily see the pieces and split them up.

Image Courtesy of General Chemistry Steps

---

🗂️ Purity & Separation Methods

Chemists often want to separate a mixture into its components in chemical experiments.

There are several ways to separate mixtures, but the most common ways are:

• Filtration - separates solids from liquids
• Distillation - separates based on boiling points
• Chromatography - separates based on movement through a medium

Let’s discuss each of these in a bit more detail.

Filtration

Filtration is a technique used to separate solids from liquids using a porous barrier or filter that allows only the fluid to pass through. This technique works because of the size difference between the particles in the mixture and the pores of the filter used.

Image Courtesy of BBC.

If you have a mixture of sand and water, you can use this technique to filter the sand out. It can get trapped by the filter paper and get left behind.

Distillation

Distillation is a separation technique used to separate components of a liquid mixture based on differences in their boiling points. The process involves heating the mixture to vaporize the component with the lowest boiling point, then cooling the vapor to condense it back into a liquid, which is collected separately.

Image Courtesy of Britannica.

Think about a mixture of water and alcohol. Since the boiling point of alcohol is lower than that of water, the alcohol is going to evaporate first. Therefore, the vapor collected will contain more alcohol than water.

Chromatography

Chromatography is a broad range of techniques designed to separate, identify, and quantify components in a mixture based on differences in their distribution between a stationary phase and a mobile phase. The components move at different speeds, causing them to separate.

There are several types of chromatography, including:

• Paper Chromatography: Uses paper as the stationary phase and a solvent as the mobile phase.
• Thin-Layer Chromatography (TLC): Uses a thin layer of material (such as silica gel) coated on a plate as the stationary phase.
• Gas Chromatography (GC): Separates volatile substances in a gaseous mobile phase interacting with a liquid or solid stationary phase.
• Liquid Chromatography (LC): Involves a liquid mobile phase passing through a column containing the stationary phase.

You’ll likely only have to understand thin-layer chromatography for this class. You may not cover this technique at all! It depends on your instructor.

---

⭐ Closing

You made it through and can now concretely discuss what matter is! Remember that these concepts build upon each other. Mastery in understanding matter provides a strong foundation for further chemistry studies. If possible, try to do a couple of experiments about this topic as it’ll help solidify your understanding of this topic!