Pure Substances and Mixtures Study Guide

Dmitri Mendeleev
- He was a Russian chemist and inventor who formulated the Periodic Law.
- He organized the periodic table of elements based on atomic weight and similar chemical properties.
- His organizational system allowed him to successfully predict the properties of eight elements that had not yet been discovered.

Definition of Matter
- Matter encompasses everything around you.
- It is defined as anything that possesses mass and occupies space (volume).
- Atoms and molecules are the constituent components of all matter.
Solid Phase of Matter
- Characterized by a definite volume and a definite shape.
- The molecules within a solid are tightly packed together.
- Solids do not flow easily because the particles are locked in place and cannot move or slide past one another.
Liquid Phase of Matter
- Characterized by a definite volume but no definite shape.
- This phase flows easily because particles can move and slide past one another.
- There is a significant amount of free space between particles compared to solids.
- Liquids take the shape of the container they inhabit.
Gas Phase of Matter
- Characterized by having no definite shape and no definite volume.
- There is a large amount of free space between particles.
- Gases flow easily as particles move freely past one another.
- A gas takes both the shape and the total volume of its container.

Definition of Pure Substances
- These possess a definite (certain) and constant (same) composition or set of ingredients.
- The composition of a pure substance does not vary; it is the same throughout the entire sample.
- Pure substances can be classified as either an element or a compound.
- Real-world examples include salt or sugar.
Elements
- An element is a substance that cannot be broken down into any other simpler substance.
- Elements are represented on the periodic table by specific symbols.
- Example: $Au$ represents Gold.
- Single atoms are represented by symbols like $H$ , while molecules of elements are represented by formulas like $H_2$ .
Compounds
- A compound is a substance formed when two or more elements have chemically combined through a chemical reaction.
- This chemical reaction results in the formation of an entirely new substance.
- Compounds are represented by chemical formulas.
- Example: $NaCl$ (Sodium Chloride or salt) and $H_2O$ (water).
Identifying and Counting Elements in a Compound
- To determine the number of different elements in a compound, count the number of different capital letters or unique element symbols present in the formula.
- Example: In the formula $Na_2O$ , there are two distinct elements represented: $Na$ (Sodium) and $O$ (Oxygen).

Definition of Mixtures
- A mixture is a combination of many different elements or substances.
- Unlike compounds, the components of a mixture are NOT chemically combined.
- Mixtures can be physically separated into their original components.
- Example: Trail mix.
Homogeneous Mixtures
- The prefix "homo" indicates sameness.
- These mixtures have a uniform appearance throughout the sample.
- Many homogeneous mixtures are referred to as solutions.
- Examples include salt dissolved in water, sugar dissolved in water, apple juice, and tea.
Heterogeneous Mixtures
- The prefix "hetero" indicates difference.
- These mixtures consist of substances or phases that are visibly different.
- They can involve different states of matter: gas, liquid, and solid.
- Examples include sand in water, oil and water, a mixture of sulfur and iron, and granite.

Definitions
- A solution is a specific type of homogeneous mixture that appears to be one single substance.
- Examples include tap water, vinegar, and gold jewelry.
- The process of making a solution involves one substance dissolving into another.
Components of a Solution
- Solute: This is the substance that is being dissolved. It is typically found in the smaller amount within the mixture.
- Solvent: This is the substance in which the solute dissolves. It is the component found in the greatest amount within the mixture.