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Classifying Matter
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Classifying Matter

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  • chalk = calcium carbonite (CaCH3) ammonia = NH3
  • Jell-O is a colloid: a heterogeneous mixture with particles larger than those in a solution, but not large enough to settle out. Milk, paint, and mayo are, too (and aerosols).
  • brass = copper + zinc vinegar = acetic acid and water.
  • CuSO4 = copper sulfate
  • Quick review on rounding to a whole number: Jeanne's method: circle the one's place number draw arrow to number on the right if it's 5 or above, the circled number is raised one digit if it's 4 or below, the circled number STAYS THE SAME In the example here, round the mass to 96. Neutrons = 96-42 = 54 Isotopes: One of two or more atoms that have the same atomic number (the same number of protons) but a different number of neutrons. Carbon 12, the most common form of carbon, has six  protons and six neutrons, whereas carbon 14 has six protons and eight neutrons. Isotopes of a given element typically behave alike chemically. With the exception of hydrogen, elements found on Earth generally have the same number of protons and neutrons; heavier and lighter isotopes (with more or fewer neutrons) are often unstable and undergo radioactive decay .
  • Don't go into too much detail at this point about valence electrons and reactivity.

Classifying Matter Classifying Matter Presentation Transcript

  • Classifying Matter Basic Chemistry Heartlife Physical Science
  • Matter - What is it?
    • Matter is anything that:
      • has mass
      • takes up space
    • All matter is made up of atoms
      • more than 100 different kinds
      • two or more combined (joined) atoms make a molecule
    • Elements are substances made from only one type of atom
      • i.e. gold, carbon, helium, neon, sulfur
    • Compounds are substances made from two or more different combined elements
      • ratios remain constant (there will always be twice as much Helium as Oxygen in water)
      • i.e. carbon dioxide, sodium chloride (salt), iron oxide (rust), ammonia, water, chalk
    Oxygen Molecule O 2 Water Molecule H 2 O Oxygen atom O
  • Mixtures
    • A mixture is made of different substances (elements or compounds) that can be physically separated
      • contain different ratios of substances
      • examples:
        • some fruit salad might have more grapes than bananas
        • some granite has more feldspar in with the mica than others
    Granite
      • How can substances be separated out of mixtures?
        • by hand or with tweezers
        • evaporation or distillation
        • filtering
        • settling in layers (centrifuge)
        • magnets
  • Mixtures - Fruit Salad vs. Whipped Cream
    • Heterogeneous mixtures are unevenly mixed
      • different substances clump together
      • easily identified as separate substances
      • examples: granite, soil, sand, salad dressing, OJ
    • Homogeneous mixtures are evenly mixed
      • particles are uniformly dispersed (spread out)
      • even with a microscope, different substances can't be identified
      • examples: air, brass, antifreeze, whipped cream, apple juice
  • Solutions
    • A solution is a homogeneous mixture in which one or more solutes (particles of a substance) are distributed uniformly throughout another substance (the solvent )
      • solutes & solvents can be solids, liquids or gases
      • the solvent is the substance in greatest quantity in the solution
    • Examples:
      • air is a solution of several different gases (O 2 , CO 2 , Ar) equally distributed in Nitrogen gas
      • alloys (such as sterling silver or dental fillings) are solid solutions
      • carbonated drinks are sugar, flavorings and carbon dioxide gas solutes uniformly dispersed in water
  • Summing up the "Matter"
  • Properties of Matter
    • Physical properties : observed characteristics that describe a substance
      • State of matter (solid, liquid, gas, plasma, B-E condensate)
      • Melting and boiling point
      • Size, density, mass, volume
      • Temperature, color , texture, etc.
    • Chemical properties : characteristics that describe how a substance's composition can change (undergo a chemical reaction)
      • Flammability
      • Susceptibility to rust (oxidation state)
      • Resistance to decomposition
      • Reactivity to other substances
      • Toxicity
  • Chemical Formulas
    • Each element has a symbol
      • O for Oxygen, C for Carbon, Cl for Chlorine, etc.
      • Periodic Table of the Elements lists these symbols
    • A compound's chemical composition can be written out as a formula showing the ratio of different elements
    • The subscript # refers to the symbol before it
    • Example: Water
      • For every one atom of Oxygen, there are two Hydrogen atoms
    H 2 O Water NaCl Sodium Chloride CH 4 Methane H 2 O 2 Hydrogen peroxide CO Carbon monoxide CO 2 Carbon dioxide NH 3 Ammonia Chemical Formula Compound Common Compounds
  • Physical vs. Chemical Changes
    • When matter undergoes a physical change:
      • it alters the state, shape or appearance
      • it retains it's chemical composition
      • the original matter can be recovered
        • i.e. wood is still wood after being cut or shredded into sawdust, but its size and shape may change
    • When matter undergoes a chemical change:
      • it changes into a totally different type of matter
      • it's chemical composition changes (atoms and molecules are broken apart or combined differently to form new substances)
      • the original matter cannot be recovered
        • i.e. wood that is burned changes into charcoal and ashes
  • Examples of Physical & Chemical Changes You fry an egg. Your body digests food.  You take an antacid to settle your stomach.  A match is lit. Food scraps turn into compost.   Hydrogen peroxide bubbles in a cut.  Rubbing alcohol evaporates on your hand. Gasoline is ignited. A juice box in the freezer freezes. Rust forms on a nail left outside. Water evaporates from the ocean's surface. Bread becomes toast. Butter melts on warm toast. Jewelry tarnishes. Clay is molded into a new shape. Milk goes sour. Aluminum foil is cut in half. Chemical Changes Physical Changes
    • Atoms are the smallest particles comprising matter
      • every atom is made up of
        • at least one positively charged proton
        • one or more neutrons (except hydrogen)
        • one or more shells of negatively charged electrons
    What is matter made of? in a dense, central nucleus Atoms are mostly empty space!
  • Nuclear Particles
    • Protons
      • located in the nucleus of an atom
      • each proton has a positive (+1) charge
      • "heavy" (has a significant mass)
    • The number of protons in an atom determines the type of element
      • 1 proton = Hydrogen
      • 3 protons = Lithium
      • 8 protons = Oxygen
    • # of protons can be found on the periodic chart as the atomic number
    p +
  • Nuclear Particles
    • Neutrons
      • located in the nucleus
      • neutrons have no charge (0)
      • "heavy" (has a significant mass)
    n 0
    • The number of neutrons varies within elements
      • # of neutrons can be determined using the periodic chart
        • atomic mass = average weight of protons & neutrons combined (taking into account all its isotopes )
        • neutrons = atomic mass (rounded to nearest whole #) minus the atomic number
  • Orbiting Particles
    • Electrons
      • travel around the nucleus in a circular pattern
        • impossible to know the exact position or velocity
      • each electron has a negative (-1) charge
      • "light" (contributes virtually nothing to the mass of an atom)
    e -
    • The number of electrons usually equals the number of protons (atomic #)
      • When the # of negative charges (electrons) equals # of positive charges (protons), they balance out.
      • Sometimes there are extra or missing electrons.
        • This results in an ion (net (-) or (+) charge on the atom)
  • Electrons in Motion
    • Electron Shells (also called energy levels or orbitals) show where electrons are likely to spend most of their time.
      • Each shell holds a different maximum number of electrons.
      • A better description of where electrons hang out is the term "electron cloud"
    • Electrons are happiest
      • in pairs
      • with full shells
    • Lone electrons are unstable and highly reactive!