solutions, acids and bases. solution formation a solution is a homogeneous mixture of two or more...

Solutions, Acids and Bases

Solution Formation

• A solution is a homogeneous mixture of two or more substances (Unit 1)

• A solution has two parts: – Solute– Solvent

Solutes and Solvents

• A solute is a substance whose particles are dissolved in a solution

• A solvent is the substance in which the solute dissolves

Solutes and Solvents cont.

Example: In a solution of seawater, salt is the solute and water is the solvent

- Salt dissolves in water

Dissolving

Substances can dissolve in three ways:

DissociationDispersionIonization

Dissociation

• Dissociation is the process in which an ionic compound separates into ions as it dissolves

Dispersion

• Dispersion is the breaking apart of a compound into small pieces – Sugar in water

Ionization

• The process in which neutral molecules gain or lose an electron– Ions in the solution are formed by the reaction of

the solute and solvent

Properties of Liquid Solutions

• Liquid solutions share three physical properties

ConductivityFreezing PointBoiling Point

Conductivity

• Conductivity is an object’s ability to conduct electricity

• HCL gas is a poor conductor of electricity, however HCL in liquid form easily conducts an electric current– Due to ionization of the HCL in water

Freezing and Boiling Points

• Freezing point: The temperature at which a substance freezes and becomes a solid

• Boiling Point: The temperature at which a substance begins to boil, creating a gas

Freezing and Boiling Points cont.

• Fresh water freezes at 0 degrees Celsius

• Saltwater freezes at -6 degrees Celsius – With a 10% salt solution – The more salt you add, the lower the freezing

point will be

Factors That Affect Rates of Dissolving

• Surface Area: The larger the surface area, the quicker the substance dissolves

• Stirring: Stirring a solution will speed up dissolving

• Temperature: An increase in temperature increases the dissolving rate

Acids and Bases

• A solution can either be an acid or a base depending on which properties a solution takes on as well as by indicating an acid or a base by using the pH scale

Identifying Acids

• An acid is a compound that produces hydronium ions (H3O+) when dissolved in water

HCL + H2O H3O+ + Cl-

Properties of Acids

Sour tasteReactivity with metals

Ability to produce color changes in indcators

Sour Taste: Foods that taste sour often contain an acid- Citrus fruits (lemons, limes, etc.) naturally

contain citric acid

Reactivity with metals: Acids may dissolve weak metals

Color Change: On a pH indicator, acids will turn a certain color

Bases

A base is a compound that produces hydroxide ions (OH-)

NaOH Na+ + OH-

Properties of Bases

Bitter taste – Objects that taste bitter contain a base

Slippery Feel – Bases often have a slippery feel to them

Color Change – Bases change a certain color when tested for pH levels

Strengths of Acids and Bases

The strength of an acid or base can be indicated by the pH scale

pH Scale

• A scale from 0-14 – 0 = most acidic– 14 = most basic

Pure water has a pH of 7

Acid, Base, or Neutral?

Lemon Juice?

Milk?

Ammonia (found in household cleaners)?