Elements

Elements, The Simplist Substance A pure substance that cannot be broken down into simpler substances by physical or chemical means. Pure Substance: Substance in which there is only one type of particle Each element contains only one type of particle (atoms)

Properties of Elements Each element has its own characteristic properties that will help identify the element. Physical properties Boiling point Melting point Density Chemical properties Reactivity Flammability Elements may share similar properties, but have other properties that will identify the substance.

Classifying Elements by Their Properties Categories of Elements: Metals: (Most Elements) Shiny Conduct heat energy and electric current Iron, nickel, cobalt Nonmetals: Dull (solid) Do not conduct heat energy and electric current Carbon, sulfur, iodine Metalloids: Properties of both metals and nonmetals

Compounds Compound: Substance that is composed of two or more elements that are chemically combined. Combine by reacting (reactivity; chemical property) Made up of molecules Formed when atoms of 2 or more elements join Elements join in a specific ratio according to their masses to form a compound A ratio of a certain compound is always the same. Hydrogen to oxygen 1:8 to form water.

Properties of Compounds May be identified by both physical and chemical properties. Properties of compounds differ from those of the elements that form them. Ex: Sodium Chloride (Table Salt) Sodium reacts violently with water Cholorine is a poisonous gas Properties: Compounds vs. Elements

Breaking Down Compounds Some compounds may be broken down into elements by chemical change. Some break down into simpler compounds. Carbonic Acid breaks down into carbon dioxide and water. Break down through chemical change Need energy Heat Electric current (electrolysis) Methods of Breaking Down Compounds

Compounds in Your World Food School Supplies Clothes Compounds found in nature usually need to be broken down for use in industry. Aluminum – produced by breaking down aluminum oxide Ammonia - nitrogen + hydrogen Proteins are compounds found in living things Need the element nitrogen to make proteins Carbon Dioxide is needed by plants to produce carbohydrates Produce energy for plants and animals Compounds in Industry Compounds in Nature