Solubility Curve Day 2

Solubility Solubility- maximum amount of substance that can be dissolved in a given amount of solvent Solubility depends on temperature, pressure, and type of solvent being dissolved Solubility is not affected by agitation and surface area.

SolubLE By soluble we mean capable of being dissolved. Suppose a sugar cube is dropped into a glass of water. You know from experience that the sugar will dissolve. Sugar is described as “soluble in water” By soluble we mean capable of being dissolved. All traces of the sugar are gone but we know it is there because the water tastes sweet throughout. This mixture is now a solution. Solvent: The dissolving medium in a solution; what dissolves another substance. Solute: The substance being dissolved in a solution.

Solute and Solvent Solute Solvent Aqueous Solution

Solubility A saturated solution contains the maximum quantity of solute that dissolves at that temperature. A unsaturated solution contains less than the maximum amount of solute that will dissolve in a given amount of solvent.

Saturated & Unsaturated

supersaturated A supersaturated solution contains more than the maximum amount of solute that can dissolve at a particular temperature. (Not all solute is dissolved)

saturated Solution

Factors that affect solubility

Solutions Example Solute Solvent Solid Liquid Gas Brass (Zinc & Copper) Sugar in water Alcohol in water Fog (water in air) Soda (Carbon dioxide in syrup) Air (Oxygen in Nitrogen)

SOLUBILITY OF SOLIDS “LIKE DISSOLVES LIKE”

Effect of Heated solvent on dissolved gases INCREASING TEMPERATURE When a solution is heated, the dissolved gases held within are let off and decrease. The kinetic energy increases causing the molecules of the solvent to move more rapidly. As the molecules move they provide space for the dissolved gases to move. The gas is less dense than the liquid so it will rise to the surface and be let off.

Temperature A warm liquid will dissolve more solute-solid than a cold liquid. An increase in temperature will result in an increase in solubility of a solid in a liquid. This is not the case for everything. Have you ever observed bubbles forming before the water reaches boiling point. These bubbles are dissolved atmospheric gases escaping from the water.

Temperature & Dissolved Oxygen Oxygen and Nitrogen become less soluble in water as the temperature increases. When an industrial plant take COOL water from a lake and then dumps HOT water back in the lake, the temperature of the entire lake increases. Such a change in temperature is known as THERMAL POLLUTION The increase in temperature lowers the dissolved oxygen in the lake. The lower amounts of dissolved oxygen can harm the aquatic animals and plants in the lake.

EFFECT OF HEATED SOLVENT ON DISSOLVED GASES (Continued) DECREASING TEMPERATURE When solvents cool they can hold more gas. As the temperature decreases the kinetic energy decreases. As the kinetic energy decreases the molecules move closer together and move less. Gases get trapped between the molecules of the cooling solvent keeping it in solution.

Pressure & solubility If there is an increase in the pressure of a gas there is also an increase in the solubility of the gas. Ex: Carbonated beverages- Once you pop the top on a Coke, The external pressure has been reduced, and the solubility of CO2 goes down. This is why Coke goes flat once you open it. Pressure does NOT have any significant effect on the solubility of liquids or solids in water (solvent).

Types of Mixtures Mixtures are classified by how thoroughly the substances mix Heterogeneous and Homogeneous Mixtures Solutions, Suspensions, Colloids

Matter Flowchart MATTER MIXTURE PURE SUBSTANCE yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound MIXTURE PURE SUBSTANCE yes no Can it be chemically decomposed? Is the composition uniform? Element

Mixtures Mixture: A physical change resulting in 2 or more substances mixed together Mixtures can be separated by Physical Means. Each substance keeps its own identity.

Heterogeneous vs. Homogeneous Mixtures Characteristics of Heterogeneous Mixtures Not same throughout Uneven distribution Particles are large enough to see, and can be separated from mixture easily. Characteristics of a Homogeneous Mixture Same throughout Even distribution Solution Particles are very small and not easily seen or separated

Solutions vs. Suspensions Solution- a homogeneous mixture of two or more substances in a single physical phase. Examples: salt and water, sugar and water, copper(II) chloride and water Suspension- heterogeneous mixture containing solid particles that are sufficiently large for sedimentation Suspensions are "murky" or "opaque". They do not transmit light. The mixture of particles can be separated by filtration. Example: sand and water

Mixtures Colloid – is a type of mixture that never settles Its particles are larger than in a solution but not heavy enough to settle Milk and gelatin are examples of colloids Milk is a mixture of water, fats, and proteins in varying proportions and its components will never settle if left standing Tyndall Effect – the scattering of lght by colloidal particles Solutions don’t scatter light because their particles are to small Think of what fog does to light  fog is a colloid The light beam is not visible as it passes through a true solution (left), but it is readily visible as it passes through colloidal iron (III) oxide in water

Consider this Phase Diagram What process is occurring when a substance changes from point X (180 °K and 0.03 atm) to point Y (160 °K and .065 atm)? A) Melting (Fusion) B) Evaporation C) Deposition D) Condensation Y X

Which of the following processes is exothermic? A) A gas changes to a liquid B) A solid changes to a liquid C) A liquid changes to a gas D) A solid changes to a gas

Which of the following particles is an electrolyte? A) SO2 B) Al2(SO4)3 C) N2H4 D) CH4

The forces that keep atoms in a molecule together are called? A) Strong Covalent Bonds B) Weak Intermolecular Forces C) Weak Ionic Bonds D) Strong Intramolecular Forces

Between points X and Y, which of the following would be observed? A) Liquid and vapor will be present B) Solid and liquid will be present C) Only liquid will be present D) Only solid will be present X Y

Consider this Phase Diagram At what temperature does the normal boiling point occur? A) 195.3 °K B) 195.4 °K C) 239.8 °K D) 405.5 °K