Chemistry – Matter Unit • What is matter? • What is chemistry? • What is the organization of matter? • What is the nature of matter?
What is NOT Matter? • Energy !
Types of Energies • Mechanical • Chemical • Heat • Atomic • Light • Electrical
Is Air matter? • What are the two criteria for matter? • Does it take up space? • Does it have mass?
What is chemistry? • “Chemistry is the study of the composition, structure, and the properties of matter and the changes it undergoes.” • All chemical reactions involve energy.
What is the composition of matter? Matter Pure Matter Substance Impure Matter Mixture
What is a pure substance? • A pure substance has a definite composition (proportion). • The composition of a substance will have the same percent of elements no matter where the sample was obtained. • Water from Lake Okechobee and water from the Atlantic Ocean (once cleaned up) will have the same composition of hydrogen to oxygen. • Gold is the same as other gold (once cleaned up).
What is a pure substance? • A puresubstance, by definition, is an element or a compound. • A container with an almost pure compound:
Pure Substance Pure Substance Compound Element
What is an element? • “a pure substance made of only one kind of atom” • A substance that cannot be decomposed any farther by simple chemical means • An element has a definite composition. Gold from South Africa is the same, when purified, as a sample from California.
Periodic Table of Elements • Most elements on the periodic chart are metals. • Elements through 114 but not 113 have been discovered or made.
Elemental Samples • Zinc, copper, lead, carbon, sulfur
What is a compound? • “A compound is a substance that is made from the atoms of two or more elements that are chemically bonded.” • The definition is actually more involved than this.
What is a compound? • A compound is a substance that cannot be decomposed any farther by simple physical means. • A compound has a definite composition by mass. • A compound is made up of two or more elements chemically combined.
What is a compound? • A compoundno longer has the properties of its constituent elements. • Table salt, NaCl or sodium chloride, is a compound of the element sodium and the element chlorine.
Sodium metal • Soft, can be cut with a knife • Shiny • Good conductor of electricity • Very reactive
Chlorine gas • Greenish gas • Poisonous • Heavier than air
Sodium chloride, NaCl • Sodium chloride dissolves in water rather than reacts with water. • Sodium chloride is a white solid, not a poisonous green gas. • Sodium chloride is its own substance with its own properties, not those of either sodium or chlorine.
Samples of Other Compounds • Sucrose (table sugar), Sodium Chloride, Water, Copper(II) sulfate
Colored Compounds • Cobalt(II) chloride, Iron(II) sulfate, Potassium dichromate, Potassium chromate, Nickel(II) nitrate, copper(II) sulfate
What is the composition of matter? Matter Pure Substance Impure Matter Mixture
Impure Matter - Mixture • “A mixture is a blend of two or more kinds of matter, each of which retains its own identity and properties.” • A mixture is made up of two or more substances that are not chemically combined.
Mixtures • Mixtures can be separated by simple physical means. • Two mixtures containing the same substances may not have the same proportions. • Example: Very salty water versus barely salty water. Very sweet sugar water versus slightly sweet sugar water.
Water and Dye Mixture • Two mixtures of the same substances may have different proportions.
Mixtures Mixtures Homogeneous Mixture Heterogeneous Mixture ?
Solutions • Mixtures • Mixture = a blend of two or more kinds of matter, each of which retains its own identity and properties a) homogeneous mixture = a mixture that is uniform in composition throughout Ex: Food coloring and water b) heterogeneous mixture = a mixture that is NOT uniform in composition throughout Ex: Oil and water
Heterogeneous Mixtures • Sand and water on the left and sand and gravel on the right.
Types of Mixtures: 1) solution = a homogeneous mixture 2) suspension = a mixture in which the particles are so large that they settle out unless the mixture is constantly stirred or agitated Heterogeneous mixture Ex: Sand and water • 3) colloid = a mixture consisting of particles that are • intermediate in size between those in solutions and those in suspensions • Heterogeneous mixture • Ex: Milk
Colloidal Suspension • Fog
THE NATURE OF SOLUTIONS: • Solvent= the substance that does the dissolving in a solution a) Typically present in the greatest amount b) Typically a liquid c) Water is the most common or “universal” solvent 2) Solute = substance being dissolved in a solution a) Typically present in the least amount b) Typically a solid
Factors Affecting the Rate of Dissolving (Increase Solution Rate): • 1) Grinding: increases surface area • 2) Stirring: allows solvent continual contact with solute • 3) Heating: increases kinetic energy; increases mixing
SOLUBILITY: 1) Solubility = quantity of solute that will dissolve in specific amount of solvent at a certain temperature. (pressure must also be specified for gases). • Ex: 204 g of sugar will dissolve in 100 g of water at 20°C • solubleand insoluble are relative terms • solubility should NOT be confused with the rate at which a substance dissolves 2) saturated solution = a stable solution in which the maximum amount of solute has been dissolved.
3) solution equilibrium = state where the solute is dissolving at the same rate that the solute is coming out of solution (crystallizing). a) Opposing processes of the dissolving and crystallizing of a solute occur at equal rates. b) solute + solvent solution
4) unsaturated solution = a solution that contains less solute than a saturated solution under existing conditions 5) supersaturated solution = a solution that temporarily contains more than the saturation amount of solute than the solvent can hold (unstable)
3 FACTORS EFFECTING SOLUBILITY: The extent to which a given solute dissolves in a solvent depends on the identity of the solute and solvent and also on the existing conditions of pressure & temperature • 1) Nature of solute and solvent • “Like dissolves like” = rule of thumb for predicting whether or not one substance dissolves in another • • “Alikeness” depends on: • o Intermolecular forces • o Type of bonding o Polarity or nonpolarity of molecules: ionic solutes tend to dissolve in polar solvents but not in nonpolar solvents
2) Pressure: a)Pressure has little effect on the solubility of liquids or solids in liquid solvents. b)The solubility of a gas in a liquid solvent INCREASES when pressure increases. It is a direct relationship.
3) Temperature: a)The solubility of a gas in a liquid solvent DECREASES with an increase in temperature. b)The solubility of a solid in a liquid solvent MOST OFTEN increases with an increase in temperature. However, solubility changes vary widely with temperature changes sometimes decreasing with temperature increases.
Mixtures vs. Compounds • Rocks are mixtures. • Minerals are pure substances • Granite rock
Mixtures vs Compounds • Minerals are pure substances although many have impuities that must be cleaned up first.
Minerals Amethyst Halite Diamond