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CHEMISTRY, ELEMENTS AND COMPOUNDS
An element is the simplest form of matter that has unique properties and includes all substances on the periodic table, while a compound contains two or more elements bonded together and can be broken down into simpler substances through chemical means. Compounds have different properties from their constituent elements, as sodium is an explosive metal, chlorine is toxic gas, but together they form the compound sodium chloride, which is table salt. Chemical changes involve the formation or breakdown of compounds through chemical reactions that conserve mass according to the law of conservation of mass.
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CHEMISTRY, ELEMENTS AND COMPOUNDS
- 1. Elements and Compounds QBA Miguel A. Castro Ramírez
- 2. Elementary… “Elementary, my dear Watson.” Fundamentals or basics
- 3. 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”
- 4. 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.
- 5. 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)
- 6. Compounds Breaking down compounds must involve a chemical change. Dissolving salt – Physical Boil water – Physical Heat sucrose - CHEMICAL
- 7. 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.
- 8. Matter Substances Mixtures Homogeneous Heterogeneous Elements Compounds Mixtures Mixtures
- 9. Symbols and Formulas One- and two-letter symbols used to identify elements Chemical formulas used to identify compounds Many elemental symbols reference the element’s LATIN name.
- 10. More Information onChemical Changes
- 11. Chemical Changes Also called chemical reactions During a chemical change, compounds can be formed, broken down, or both
- 12. Chemical Reactions Starting substances are called REACTANTS Ending substances are called PRODUCTS
- 13. Chemical Reactions Can result in formations of solids, liquids, or gases Precipitate – solid that forms within a liquid and settles out
- 14. Law of Conservationof Mass
- 15. Law of Conservationof 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.
- 16. Questions to ThinkAbout 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.
- 17. 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, the 2. “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.