Elements and Compounds QBA Miguel A. Castro Ramírez
Elementary… “Elementary, my dear Watson.” Fundamentals or basics
An Ancient Definition Aristotle first classified matter as “elements”. “one of those bodies into which other bodies can be decomposed and which itself is not capable of being divided into other”
Elements Substances can be considered elements or compounds An element is the simplest form of matter that has a unique set of properties. All substances found on periodic table are elements.
Compounds A compound is a substance that contains two or more elements bonded together Can be broken down into simpler substances by CHEMICAL means (elements cannot)
Compounds Breaking down compounds must involve a chemical change. Dissolving salt – Physical Boil water – Physical Heat sucrose - CHEMICAL
Properties of Compounds Properties of compounds are usually different from their component elements Ex. Sodium is an explosive metal. Chlorine is a toxic, green gas. Sodium chloride is table salt.
Law of Conservation of Mass During any chemical reaction, the mass of the products is always equal to the mass of the reactants. Therefore, matter is neither created nor destroyed during a chemical reaction, only changed.
Questions to Think About Each group of 3 should answer all 6 questions. Questions should be answered neatly and completely. Your participation will be factored into your quarter grade.
1. Physical Change or Chemical 4. Propose a multi-step solution Change? to separating the following a) Dissolving sugar in iced tea mixture: iron fillings, sand, b) A bicycle rusting on the lawn salt, cooking oil, and water. c) Scrambling an egg d) Cooking the egg e) Recycling plastic bottles into 5. Explain why this statement is plastic benches false. Give examples. f) Burning plastics for energy “Because there is no change in composition during a physical change, the2. “Fools gold” is a compound appearance of the substance known as pyrite (iron and will not change.” sulfur). When completely broken down, a 45.2-g sample yields 21.0 g of iron. How much 6. Every day you encounter sulfur is produced? Explain. chemical changes that are harmful and that are helpful to humans or the environment.3. Explain this statement: “A gas Name at least two of each. requires a container but a solid Also, write how you KNOW is its own container. that it is a chemical change.