UNIT 1 Introduction to Chemistry

CLASSIFICATION OF MATTER

Matter Chemistry involves the study of the structure, composition, properties, and the behavior of matter. Matter is the physical material of the world It has mass, volume, and inertia > 100 elements constitute all matter Scientists use Kinetic Molecular Theory (KMT) as a way to model the structure of matter All matter can be classified according to its phase and its composition

Kinetic Molecular Theory KMT states the following: All matter is composed of tiny particles. These particles are in constant motion. The amount of motion is proportional to temperature. Increased temperature means increased motion. Solids, liquids and gases differ in the freedom of motion of their particles and the extent to which the particles interact.

Phases of Matter All matter can be classified into 4 phases (physical states) Solid – definite volume and shape; particles packed in fixed positions Liquid – definite volume but indefinite shape; particles close together but not in fixed positions Gas – neither definite volume nor definite shape; particles are at great distances from one another Plasma – high temperature, ionized phase of matter as found on the sun. The amount of internal thermal energy (heat) determines the state of matter.

Composition of Matter Matter Pure Substance Element Compound Mixture Homogeneous Mixture Heterogeneous All matter can be divided up into four main categories.

PHYSICAL / CHEMICAL PROPERTIES & CHANGES

Properties of Matter Property – any characteristic that allows us to recognize a particular type of matter and to distinguish it from other types of matter Each substance has a unique set of physical and chemical properties. Physical Properties are measured without changing the substance. e.g., color, density, odor, melting point Chemical Properties describe how substances react or change to form different substances e.g., rusting of an iron nail at room temperature, sodium reacts violently with water, radioactive decay, lack of reactivity

Properties of Matter-Practice DIRECTIONS: Classify each of the following properties as either physical or chemical. Blue color Density Flammability Solubility Reacts with acid to form hydrogen gas Supports combustion Sour taste Melting point Reacts with water to form a gas Hardness

Using Properties of Matter Separation techniques exploit the differences in properties of matter Filtration - remove solid from liquid Distillation - boil off one or more components of a mixture Chromatography - exploit the solubility of components

accompanied by a transfer of energy*** Changes of Matter ***Both physical and chemical changes are ALWAYS accompanied by a transfer of energy*** PHYSICAL CHANGE - changes in the physical properties of matter Properties of a material change but the composition remains the same

Changes of Matter 3 basic categories Phase change (e.g. melting, freezing, condensing, sublimation, etc.) Mechanical change (e.g., ripping, chopping, breaking, cutting, etc.) Dissolving a solute into a solvent (e.g., forming a solution from CuSO4) Can be classified as reversible and irreversible Which of the above would be reversible/irreversible?

Changes of Matter CHEMICAL CHANGE-one or more substances transforms into one or more chemically different substances Composition of matter ALWAYS changes (i.e., change in identity) Created by chemical reactions

Changes of Matter Indicators of a chemical reaction: Color change Formation of a gas Formation of a solid Formation of an odor Heat/light released/absorbed Change in pH

Changes of Matter DIRECTIONS: Classify each of the following examples as a physical or chemical change. Sodium hydroxide dissolves in water. Hydrochloric acid reacts with sodium hydroxide to produce a salt, water, and heat. A pellet of sodium is sliced in two. Water is heated and turned to steam. Potassium chlorate decomposes to potassium chloride and oxygen gas. Iron rusts. Ice melts. Acid on limestone produces carbon dioxide gas. Milk sours. Wood rots.

PHASE CHANGES & PHASE DIAGRAMS

Phase Changes Phase Change - transition when a solid, liquid or gas changes from one phase to another due to the increased/decreased motion of molecules Phase changes often occur due to the absorption or release of heat energy Phase changes come from the competition between temperature and attractive intermolecular forces Intermolecular forces tend to attract molecules together into rigid structures As the amount of thermal energy increases in a substance, this rigid structure is disrupted

Phase Changes SOLID - LIQUID melting - (solid to liquid) - increased molecular motion due to absorbed heat freezing - (liquid to solid) decreased molecular motion due to released heat Both occur at the same temperature called the melting point or the freezing point

Phase Changes LIQUID - GAS vaporization (boiling/evaporating) - (liquid to gas) - increased molecular motion due to absorbed heat condensation – (gas to liquid) decreased molecular motion due to released heat Both occur at the same temperature called the boiling point or the condensation point

Phase Changes SOLID - GAS sublimation - (solid to gas) - increased molecular motion due to absorbed heat deposition - (gas to solid) decreased molecular motion due to released heat

Phase Diagrams Phase Diagram (Heating and Cooling Curve) – a common way to represent the various phases of a substance and the conditions under which each phase exists.

Warming (Endothermic) Energy is absorbed GAS LIQUID / GAS LIQUID SOLID / LIQUID Cooling (Exothermic) Energy is released SOLID

(Boiling/Evaporating) Vaporization (Boiling/Evaporating) Boiling Point and Condensing Point are at the SAME temp!!! Condensing Point Boiling Point Condensing Melting Melting Point and Freezing Point are at the SAME temp!!! Melting Point Freezing Point Freezing