Unit 1 Notes on Matter: Elements, Molecules, Compounds, and Mixtures

Elements are pure substances comprised of only one specific kind of atom.
Atoms function as the most basic unit of matter.
On the periodic table, elements are represented by letters known as symbols.
The first letter of an elemental symbol is always capitalized.
Specific examples of elements include:
- $Na$ : Sodium
- $O$ : Oxygen
- $H$ : Hydrogen
- $Zn$ : Zinc

A molecule is defined as two or more atoms bonded together.
- General examples include: Oxygen ( $O_2$ ), Carbon Dioxide ( $CO_2$ ), and Water ( $H_2O$ ).
An Elemental Molecule consists of two or more of the same type of atom (element) bonded together.
- Examples include: $O_2$ and $Cl_6$ .
A compound consists of two or more different elements that are chemically bonded.
- Examples include: Sodium Chloride ( $NaCl$ ) and Water ( $H_2O$ ).
- Identification Hint: To identify a compound, look for the presence of multiple capital letters in the chemical formula.
The Relationship Rule: All compounds are considered molecules, but not all molecules qualify as compounds.

A mixture is composed of two or more different substances or types of matter that occupy the same space but are not chemically combined.
Substances within a mixture do not join together at the atomic level.
Individual Properties: Each substance in a mixture retains its individual identity and properties. For example, tomatoes in a salad do not change their nature simply because they are mixed with other vegetables.
Ratio and Proportion: Unlike compounds, mixtures do not have a set ratio of components.
- A set ratio is a fixed proportion between two things. For instance, Water ( $H_2O$ ) always has a ratio of $2:1$ (two parts hydrogen to one part oxygen), meaning it is not a mixture.
- In a mixture, such as a bag of chocolate candy, the ratio of colors (e.g., 5 greens, 5 reds, 10 browns, 5 blues, 4 yellows, and 3 oranges) is not the same every time.
Atomic Level Ratios: Mixtures lack an exact ratio at the atomic level, meaning they will not consistently have a specific count of one atom type to another.

Mixtures can be separated through physical means rather than chemical reactions.
Methods for physical separation include:
- Manually picking out pieces with hands.
- Boiling the mixture.
- Using a sieve.
- Using a magnet.
There are two primary categories of mixtures based on their composition:
- Heterogeneous Mixtures: The prefix "hetero" means unlike or mixed. In these mixtures, you can visually distinguish the different parts. Examples include salad, vegetable soup, and soil.
- Homogeneous Mixtures: The prefix "homo" means same or alike. These mixtures are evenly mixed and appear uniform throughout, making it impossible to see the different parts. Examples include solid deodorant, cheddar cheese, and chocolate pudding.

Identification Practice (Element, Molecule, or Compound):
- $HCl$ (Hydrochloric Acid)
- $Zn$ (Zinc)
- $C_6H_{12}O_6$ (Glucose)
- $H_2$ (Hydrogen molecule)
- $C$ (Carbon)
- $CO_2$ (Carbon Dioxide)
Determining Mixture Types (Can the parts be seen?):
- Cheeseburger: Heterogeneous (parts like the bun, meat, and cheese are visible).
- Soda with carbonation: Heterogeneous (bubbles are visible separate from the liquid).
- Creamy peanut butter: Homogeneous (appears uniform throughout).
- Chocolate pudding: Homogeneous (appears uniform throughout).
- Hidden Valley Ranch Dressing: Homogeneous.
- Marzetti Olive Oil and Vinegar: Heterogeneous (distinct layers are visible).
- Bubbleology: Heterogeneous.
- Listerine (Antiseptic/Mouthwash): Homogeneous.
Soil Analysis: A handful of damp soil containing grains of sand, clay, and water droplets is a mixture. It is a mixture because its parts retain their individual properties, and the ratios of sand, clay, and water vary depending on the location from which the soil was taken.