Solutions, Acids and Bases
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)?