Chapters 8 and 9 Classification and Composition of Matter

1) Matter and Temperature

    a) Matter- “stuff”; has mass and takes up space

    b) 4 Categories of Matter – These are based on the materials’ molecular motion  (how fast the molecules are moving)
            i) Solids
            ii) Liquids
            iii) Gases
            iv) Plasma

    c) Kinetic Theory of Matter – the particles that make up matter are always moving

    d) Solids – definite volume and shape; the particles are held closely together and can move but can not move out of position 

            i) Crystalline – particles are arranged in repeating geometric shape ex.  Snowflake (hexagon)
            ii) Amorphous – solids with no definite shape; Very thick liquids; ex. plastic, glass

    e) Liquids – definite volume and take the shape of the container they are in ; the particles have enough kinetic energy to move over and around each other

    f) Gases – “springy”; take the shape and volume of the container the particles are in;  can be compressed (squeezed) into other volumes;  particles have enough kinetic energy to completely separate from each other

    g) Plasma – 99% of all matter in the universe; most plasma in our solar system is in the sun; gas-like mixture of charged particles ex.  fluorescent light – electricity is passed through mercury (Hg) gas  and the gas is converted to plasma

    h) Thermal Expansion – kinetic theory also explains why matter shrinks when cooled and expands when heated (exception :  water to ice);  this is why bridges and sidewalks are built with expansion joints

    i) As matter is heated the molecules move faster, the faster molecules move the farther apart they move.

2) Changes in State
    a) Evaporation – liquid to a gas below the boiling point ex.  a bowl of water left out will eventually dry up

    b) Condensation – gas to a liquid ex.  dew on grass, “sweat” on a cup

    c) Sublimation – when a solid turns directly into a gas without ever becoming a liquid; ex.  dry ice

    d) Heat of fusion - The amount of heat energy needed to convert a solid into a liquid (ice to water) or a liquid into a solid (water to ice)

    e) Heat of Vaporization – the amount of heat energy needed to convert a liquid to a gas (water to steam ) or a gas to a liquid (steam to water)

3) Composition of Matter
    a) Objects can be described by the state of matter they are in or by the particles they are made of

    b) Element - all particles (atoms) in the matter are identical ex.  carbon, iron
        i) There are 116 known elements

    c) Compounds – two are more atoms of elements combined

        i) Molecule – smallest unit of a compound that can exist

        ii) Ex.  water = H20  = 2 atoms of hydrogen and 1 atom of oxygen

        iii) Ex.  oxygen gas = O2 = 2 atoms of oxygen combined  (this is the form of oxygen we breathe)

        iv)  In compounds, the ratio of the atoms is always the same.  Ex.  all water molecules are made of 2 hydrogen atoms and 1 oxygen atom

        v) Compounds have a different appearance than the elements that make them.
                (1) Ex.  Table sugar – white grains;  sugar is made of the elements carbon (C), oxygen (O), and hydrogen ( H); carbon is a black solid  (coal), oxygen is clear gas, hydrogen is a clear gas;  sugar tastes different than C, O, or H

    d) Physical processes can not separate elements and compounds.
        i) Ex. of physical processes – filtering impurities from water; using a magnet to pick nails out of a pile of saw dust

    e) Mixture – made of 2 or more compounds; mixtures do not always contain the same amount of substances; Ex.  Chocolate chip cookies – a combination of cookie and chips but not all cookies have the same # of chips

        i) Heterogeneous mixtures – unevenly mixed mixtures; different materials are easily distinguished; hetero  = different; Ex.  pizza, granite

            (1) Colloid – a heterogeneous mixture, that does not separate, the particles are large enough to scatter light (Tyndall Effect); Ex.  mayo, jello, milk, fog, smog

            (2) Suspension – heterogeneous mixture whose particles settle out; Ex.  muddy water

    ii) Homogeneous mixtures (Solution) – evenly mixed mixtures; homo = same; Ex.  Vinegar = a uniform mixture of water and acetic acid

4) Describing Matter
    a) Physical Properties –characteristics of matter that can be observed without changing the substance Ex.  Boiling point ( liquid to gas) (b.p. of water = 100 C); Freezing point of water (liquid to solid) (f.p. of water = 0 C); shape color, mass, density, size, magnetism

    b) Physical Changes – do not change the identity of the substance Ex.  evaporation of water ( liquid to gas);  separation of substances by filtration (cleaning water with a filter)

    c) Chemical Properties – tell you what type of chemical changes a substance can undergo; must change the substance to observe

    d) Chemical Changes – changes the identity of a substance Ex.  burning a candle; baking a cake; combustion (burning) of gas; turning food into usable energy in your body

        Grass + O2 = CO2 (gas) + H20 (gas) + carbon  (ashes)
                    (31 g)                                    (31 g)

    e) Law of Conservation of Mass – matter can not be created or destroyed during a chemical change; the mass of what you start with is the same as the mass you end with