Mixtures A combination of two or more pure substances in which each pure substance retains its own individual chemical properties –physical combination –can be separated physically –has no definite ratio SECTION 3.3 – Mixtures

Homogeneous Mixtures Mixture with a constant composition throughout –each and every part is identical –different part cannot typically be identified –also called a solution Also known as solutions, which can contain solids, liquids, or gases. A solid-solid solution known as steel is called an alloy, which is a mixture of metal & nonmetal. SECTION 3.3 – Mixtures

Heterogeneous Mixtures Mixture that is not blended smoothly throughout. –each part is NOT identical –parts of mixture are typically easy to identify SECTION 3.3 – Mixtures

Mixtures versus Compounds S Fe Physically mixed, can be separated by physical means. Chemically reacted, cannot be separated by physical means.

Separating Mixtures Filtration –uses a porous barrier to separate a solid from a liquid Distillation –uses the differences in boiling points SECTION 3.3 – Mixtures

Using physical properties to separate mixtures filtration distillation crystallization solubility bp solubility

Separating Mixtures Crystallization –results in the formation of pure solid particles of a substance from a solution containing a dissolved substance Chromatography (1) (2) (1) (2) –separates components of a mixture on the basis of the tendency of each to travel or be drawn across the surface of another material SECTION 3.3 – Mixtures

Separating Mixtures Solubility –Water is added to the mixture and one part of the mixture dissolves into the water and the remaining component can be filtered out. –The water & substance solution must then go through distillation or crystallization to remove the dissolved substance from the water. –SALT DISSOLVING IN WATER (1) (2)(1) (2) Magnetism –Process by which parts are separated out based on their magnetic properties SECTION 3.3 – Mixtures

Elements A pure substance that cannot be separated into simpler substances by physical or chemical means. –91 occur naturally –Allotropes- element is found in more than one form. Ex. Carbon- diamond & graphite, Oxygen- O 2 & O 3. –Diatomic elements- found as a pair with itself Ex. O 2, N 2, F 2, Cl 2, H 2, I 2, Br 2 –Expressed with a chemical symbol -one, two or three letters -only the first letter is capitalized -organized on the Periodic Table SECTION 3.4 – Elements & Compounds

Periodic Table  Horizontal rows-periods  Vertical row- groups/family –Elements in a group/family together have similar properties SECTION 3.4 – Elements & Compounds

Compounds Chemical combination of two or more elements –definite ratio –can only be separated by chemical changes –Compounds that occur naturally are more stable than the individual component elements. –properties of a compound are different from the properties of the elements that make it Water aspirin sugar NaCl (salt) NH 3 (ammonia) HCl (hydrochloric acid) Fe 2 O 3 (Iron III Oxide) SECTION 3.4 – Elements & Compounds

CHAPTER 3

Law of Definite Proportions A compound is always composed of the same elements in the same proportion by mass Percent mass of element by Mass = mass of compound X 100 SECTION 3.4 – Elements & Compounds

Energy The ability to do work or produce heat. Energy exists as 2 basic forms: potential energy & kinetic energy. –Potential energy- stored energy or energy due to the composition or position of an object. –Kinetic energy- energy of motion. Work = Force x Distance

Conservation of Energy States that in any chemical reaction or physical process, energy can be converted from one form to another, but it is neither created nor destroyed. It can be accounted for as heat, stored energy, or work. Heat- energy transferred from an object at higher temperature to one at a lower temp. Temperature- measure of the average kinetic energy of the particles in a system.