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What is Chemistry ?

What is Chemistry ?. Chemistry is the study of the composition of matter the study of all substances and the changes that they can undergo. Four Phases of Matter Solids. 1. Solids have definite shape & volume have strong forces between particles

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What is Chemistry ?

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  1. What is Chemistry ? • Chemistry is • the study of the composition of matter • the study of all substances and the changes that they can undergo

  2. Four Phases of MatterSolids 1. Solids • have definite shape & volume • have strong forces between particles • Therefore, the particles are very close to each other • usually the most dense phase • usually incompressible

  3. Four Phases of MatterLiquids 2. Liquids • have definite volume • take the shape of the container • “flow” and are incompressible • the forces between particles are intermediate

  4. Four Phases of MatterGases 3. Gases • have no definite shape or volume • dependent on the container they fill • have very weak forces between particles so they have very low densities • They are compressible and can diffuse

  5. Four Phases of MatterPlasma 4. Plasma • Energy is very high due to extremely high temperatures • Atoms are stripped of their electrons • “ionized” - charged • moves quickly & unevenly • Examples • the sun and lightning

  6. Law of Conservation of Mass/Energy :mass or energy can not be created or destroyed in a chemical reaction, it can only change forms. massreactants = massproducts

  7. Physical Property • Characteristic of a substance that can change without changing the substance’s composition.

  8. Physical Change • A change that does not affect the composition of a substance

  9. Examples of Physical Changes • Melting/ Freezing • Vaporizing/ Condensing • Cutting • Grinding • Squishing

  10. Chemical Property • Characteristic that describes the ability of a substance to change into a different substance.

  11. Chemical Change • Change in which a substance becomes a different substance.

  12. Examples of chemical changes • Flammability (burning) • Exploding • Fermenting • Digesting • Corroding • Tarnishing • Rusting

  13. Evidence of a chemical change

  14. Signs of a Chemical Reaction • Energy change (hot, cold, light) • Gas is produced (bubbles form without heating) • Formation of a precipitate (a solid) • Water is produced or made in the reaction • A new substance is made (color change)

  15. Physical or Chemical change • Ice melting • Cooking • Placing metal wire in acid • Placing Alka Seltzer in water • Tear paper • Boiling water • Boil potato

  16. Classifying Matter • Objectives • To learn to distinguish between mixtures and pure substances. • To learn different methods of separating mixtures.

  17. Mixtures and Pure Substances • Mixtures: a combination of two or more pure substances in which each pure substance retains its individual chemical properties • Examples: • Soda  water, sugar, carbon dioxide • Sea water  water, minerals, salt, etc. • 14 carat gold 36% gold, 25% silver, 37% copper • Dirt • Air nitrogen, oxygen, argon, helium, neon, carbon dioxide, water vapor, etc.

  18. Homogeneous Mixture: mixture that is the same throughout. Can also be called… solutions! Heterogeneous Mixture: mixture containing regions of varying composition. 2 Types of Mixtures

  19. Heterogeneous or Homogeneous Mixture?

  20. Alloys are a type of solution • Alloy • Mixture of two metals • Examples: • Bronze (copper and usually tin) • Sterling silver (92.5% silver and 7.5% other metals, usually copper) • Brass (copper with zinc)

  21. Ways to Separate a Mixture • Separation by hand • Filtration • Evaporation • Chromatography • Sublimation • Distillation

  22. How would you separate a mixture of: • Salt and water • Salt and sand • Water and alcohol • Clay and water • Different colors of ink • Two solids mixed evaporation filtration/evaporation distillation filtration chromatography sublimation

  23. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Matter Flowchart MATTER yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element C. Johannesson

  24. Matter Flowchart element hetero. mixture compound hetero. mixture solution • Examples: • iron • pepper • sugar (sucrose) • birdseed • tea C. Johannesson

  25. Pure Substances • Element • composed of identical atoms • EX: copper wire, aluminum foil C. Johannesson

  26. Pure Substances • Compound • composed of 2 or more elements in a fixed ratio • properties differ from those of individual elements • EX: table salt (NaCl) C. Johannesson

  27. Pure Substances • Law of Definite Composition • A given compound always contains the same, fixed ratio of elements. • Law of Multiple Proportions • Elements can combine in different ratios to form different compounds. C. Johannesson

  28. Pure Substances • For example… Two different compounds, each has a definite composition. C. Johannesson

  29. Classify each as an element, compound, homo/hetero mix Tap water aluminum air Polluted air store bought milk “whole” milk Sugar salt 14 K gold 24 K gold H2SO4 river water Salt water O.J. w/pulp ice & water Raw hamburger glass of Cherry Coke mercury Red Kool Aid cough medicine maple leaf Brass choc. chip cookie H2O2 Chunky peanut butter steel can of paint “bubble gum” medicine 1,3,5-trinitrotoluene

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