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Chapter 2

Chapter 2. Matter and Change. States of Matter. No definite shape No definite volume Very compressible. No definite shape Definite volume Not compressible. Definite shape Definite volume Not compressible. What is a Vapor?. Vapor = gas

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Chapter 2

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  1. Chapter 2 Matter and Change

  2. States of Matter No definite shape No definite volume Very compressible No definite shape Definite volume Not compressible Definite shape Definite volume Not compressible

  3. What is a Vapor? • Vapor = gas • Use “vapor” for a gas that is a solid or liquid at room temperature • Examples: water, bromine Water is liquid at 20C Water is vapor at 100C

  4. Substance: matter with uniform and definite composition • Element • The simplest form of matter that has a unique set of properties • Cannot be broken down by chemical means • 118 right now • Ex: carbon, oxygen, hydrogen • Compound • A substance that contains two or more elements chemically combined in a fixed proportion • Can be broken down by chemical means • Glucose - C6H12O6 • Properties are very different from the elements it is made of

  5. Mixture vs. Pure Substance Mixture Substance Fixed composition Water is always H2O Can be chemically separated • Composition can vary • Can be physically separated

  6. Mixture: physical blend of two or more components • Heterogenous • NOT uniform composition • Ex: pepperoni pizza • Homogenous • Uniform composition • Called “solution” • Can be solid, liquid, or gas • Ex: air

  7. Quick Check!Are these mixtures or substances?

  8. Quick Check!Are these mixtures hetero- or homogeneous?

  9. Heterogenous Mixtures and Phases • Phase: any part of a sample with uniform composition and properties Mixed sample has 1 phase! There are 2 phases here!

  10. Separating Mixtures Filtration: separation by size difference Chromatography: separation by polarity difference

  11. Distillation: separation by boiling point difference

  12. Properties of Matter Chemical Property Physical Property Can be observed or measured without changing the composition of a substance Ex: color, density, melting point, boiling point, hardness • How a substance reacts to form other substances • Ex: flammability, ability to react with acid

  13. Two Types of Physical Properties Extensive Property Intensive Property Depends on type of matter, not amount Color, hardness, density, melting point, boiling point • Depends on amount of material present • Mass and volume

  14. Quick Check!Are these properties of Si physical or chemical? • blue-gray color • physical • brittle • physical • does not dissolve in water • physical • reacts vigorously with water • chemical

  15. Physical Change: substance changes appearance, NOT composition Irreversible Change Reversible Change Can be undone Ex: change of state • Cannot be undone • Ex: cutting hair, ripping paper

  16. Chemical Change • Substance changes composition • H2O(l) → H2(g) + O2(g) • Ex: cooking, rotting, fermenting, rusting, exploding • Chemical change =chemical reaction (rxn)

  17. Clues for Chemical Changes • Transfer of heat • Gets hot or cold, without YOU adding the heat • Production of a gas • Bubbles appear, without YOU adding heat • Formation of a precipitate • Solid forms from liquids • Cloudiness – means solid particles are in there • Color change

  18. Quick Check!Are these chemical or physical changes?

  19. Law of Conservation of Mass • “Matter is neither created nor destroyed.” • Lavoisier, 1789 • Mass of products = mass of reactants • Need to mass precisely • Need to capture/measure gases Merci, Monsieur Lavoisier!

  20. Conservation of Mass Problems • 27 g of water is broken down into oxygen gas and hydrogen gas. If 18 g of hydrogen is produced, how much oxygen is produced? • H2O  H2 + O2 • Limonite (Fe2O3) is the mineral name for rust. If 28 g of limonite are produced from 15 g of Fe, how much O2 was used in the reaction? • Fe + O2 Fe2O3

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