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# Classifying Matter

## on Nov 28, 2011

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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&apos;s method: circle the one&apos;s place number draw arrow to number on the right if it&apos;s 5 or above, the circled number is raised one digit if it&apos;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&apos;t go into too much detail at this point about valence electrons and reactivity.

## Classifying MatterPresentation 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 &quot;Matter&quot;
• 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
• &quot;heavy&quot; (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)
• &quot;heavy&quot; (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
• &quot;light&quot; (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 &quot;electron cloud&quot;
• Electrons are happiest
• in pairs
• with full shells
• Lone electrons are unstable and highly reactive!