Chemistry Mixtures Overview

Mixtures

• Mixtures are combinations of two or more pure substances.
• Mixtures can be homogeneous or heterogeneous.
• Homogeneous mixtures have a uniform composition throughout.
• Heterogeneous mixtures have a non-uniform composition.
• Mixtures can contain different states of matter.
• Physical separation methods can be used to separate mixtures.
• Chemical methods are required to separate compounds and molecules, not mixtures.

Homogeneous Mixtures

• Homogenous mixtures appear uniform throughout.
• Particle size is typically atomic or molecular size.
• Particles are not visible to the naked eye.
• Components cannot be distinguished.
• Separated by physical means like filtration or sieving.
• Examples: solutions, metal alloys, sugar water, air, lemonade, soda.

Heterogeneous Mixtures

• Heterogeneous mixtures do not appear uniform throughout.
• Particle size is larger than atomic or molecular size.
• Particles are visible to the naked eye.
• Components can be distinguished.
• Separated by physical methods like filtration.
• Examples: blood, sand and salt, chex mix, gravel, chocolate milk

Solutions

• Homogenous mixtures of liquids are called solutions.
• A solution has a solute (the substance being dissolved) and a solvent (the substance doing the dissolving).
• The concentration of the solute is usually less than 50%.
• Examples: sugar mixed in water, salt mixed with water, vinegar and water.

Electrolytes

• Electrolyte solutions contain ions that conduct electricity.
• Examples of electrolytes include salts like NaCl and strong acids.
• Nonelectrolytes do not conduct electricity.
• Examples include sugar, ethanol and other carbon based molecules

Water as a Solvent

• Water is known as the universal solvent because it dissolves more substances than other solvents.
• Water's polarity and intermolecular forces allow it to dissolve many substances.
• "Like dissolves like" is a general rule for solubility in water: Polar substances dissolve better in water

Solubility

• Solubility refers to how much solute can dissolve in a given amount of solvent.
• Solubility of solids depends on temperature
• Solubility of gasses depends on temperature and pressure.
• Miscible substances dissolve in each other while immiscible substances do not.
• Factors affecting rate of dissolution include: temperature, agitation, and surface area.

Saturation

• A saturated solution contains the maximum amount of solute that can dissolve at a given temperature and pressure.
• An unsaturated solution holds less solute than the maximum amount it can hold.
• A supersaturated solution holds more solute than it can theoretically hold at a given temperature and pressure; it's unstable and will eventually deposit excess solute.

Solubility Curves

• Solubility curves graphically show the relationship between temperature and the solubility of a given substance.
• The area above the curve on a solubility curve represents a supersaturated solution.
• Gasses tend to be less soluble at higher temperatures