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CH1: General Chemistry

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  1. CH1: General Chemistry The Heart of the Matter

  2. Bring out ½ sheet of paper • Name the three states of matter (bonus of a half-point each if you can name the two others) • In outer space, would an apple have less mass? • Back on Earth, if we cut this apple into segments, what type of changes would occur? (physical or chemical?)

  3. Problem Solving • I have a glass jar filled with a mixture of mineral oil and acetone, both of which are colorless. Oil and acetone do not mix, and thus form two layers in the jar. Liquid A Liquid B

  4. Problem Solving • You want to know which of the liquids is acetone and which is mineral oil, but you can’t tell by the appearance alone. Thus, you conduct an experiment and find that: • 2.00 ml of acetone weighs 1.58 grams • 1.50 ml of mineral oil weighs 1.26 grams • What are the densities (in g/ml) of mineral oil and acetone? Based on this, which liquid floats on top?

  5. The Heart of the Matter • MATTER – the stuff the universe is made of. It’s anything that has mass and occupies space • MASS – the amount of matter an object contains

  6. Mass vs. Weight • Mass is constant for a given sample of matter • Weight depends on the strength of gravitational force • Will an apple have less mass in outer space? NO

  7. Classifications of matter urea • SOLID – definite volume, definite shape • LIQUID – definite volume, no permanent shape • GAS – no definite volume or shape Titration setup chlorine

  8. Atoms and molecules wiggle? • Matter moves on an atomic level – even solids. • Solids are held in rigid structures; their atoms vibrate • Liquid molecules slip and slide against each other • Motion and other forms of energy

  9. Energy and state changes • Why does heating a substance result in state changes (e.g. ice to water to steam)? • Thermal to kinetic energy

  10. Plasma: the fourth state of matter • So much energy, the electrons are ejected. • “ion soup” Plasma

  11. Examples of Plasma

  12. Absolute Zero • -273 degrees C • Outer space? • Technology: less than 1 millionth of a degree above absolute zero • Bose-Einstein condensates

  13. BEC, briefly • Atoms occupy the same space • Atoms are indistinct from each other and form one blob

  14. Test yourself • Steam • Fluorescent light • Gravel • Milk • Mercury (room temp)

  15. Classifying by composition • Pure substances vs. Mixtures • Substances: fixed composition and distinct properties (e.g. salt, water) • Mixtures: combos of 2 or more substances, each retaining its own properties (e.g. sand, milk) HETEROGENOUS HOMOGENOUS

  16. MIXTURES • COMBINATION OF TWO OR MORE SUBSTANCES IN WHICH EACH SUBSTANCE RETAINS ITS OWN CHEMICAL IDENTITY • Homogenous • heterogenous ALLOYS : Mixtures of metals eg. YELLOW BRASS (Cu, Zn) STAINLESS STEEL (Fe, Cr, Ni, C) PLUMBER’S SOLDER (Pb, Sn) STERLING SILVER (Ag, Cu) GOLD ALLOYS AMALGAMS : Metal mixtures with mercury COLLOIDS: Intermediate dispersions or suspensions (Borderline)

  17. COLLOIDS EVERYWHERE

  18. Classification “pachinko” ALL MATTER Is it uniform throughout? YES NO Heterogeneous Mixture Homogeneous e.g. SAND Can it be separated by physical means? NO YES Homogeneous Mixture (SOLUTION) PURE SUBSTANCE Can it be decomposed into other substances by chemical processes? e.g. seawater NO YES Element Compound

  19. Pure Substances • ELEMENTS – cannot be decomposed into simpler substances.

  20. Pure Substances • Elements – composed of only one type of atom • Compound – composed of two or more different types of atoms

  21. Classification Recap • States: solid, liquid, gas, plasma, BEC • Composition • Mixtures: homogenous and heterogenous • Pure substances • Elements • Compounds

  22. PHYSICAL PROPERTIES - Measurable without changing the identity and composition of the substance CHEMICAL PROPERTIES - Describe the way a substance may change or react to form other substances • INTENSIVE PROPERTIES • Do not depend on the amount of sample being examined. • Useful in identification Eg. Temp., Melting point, Density EXTENSIVE PROPERTIES - Depend on the amount of sample being examined. Eg. Mass, Volume Properties of Matter

  23. Some Physical Properties • Temperature • Color • Boiling point • Freezing point • Hardness • Density

  24. Some chemical properties • Oxidation (rusting and tarnishing) • Flammability • Inertness

  25. Changes in matter • Physical change – doesn’t entail any change in chemical composition • Chemical change – entails change in chemical structure BOTH physical and chemical change

  26. What type of change is this?

  27. Next meeting • Read about atomic theory