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Accelerated ScienceProperties of Matter
Properties of Matter
I. Pure Substance: matter that always has the same compositionEX: table salt (NaCl) is a pure substance b/c it is equally as salty throughout2 groups: elements and compounds
A. Element: a substance that cannot be further broken down into simpler substances
• 100 different known elements• Each has a unique atom• Ex: nitrogen, copper, hydrogen, uranium, carbon,
oxygen
B. Compound: made from 2 or more simpler substances
• can be broken down into those substances• Always a fixed proportion• Ex: water (H20) is a
compound of hydrogen and oxygen
There are over two million
known compounds
Do compounds behave the same as their elements?
• Not usually• EX: water is a liquid at
room temperature used to put out fires
• Hydrogen and oxygen are gases at room temperature and will fuel a fire.
• Compounds are chemically joined
II. Mixtures• Mixtures: the properties of
mixtures vary b/c the composition is not fixed or chemically joined
• Analogy: Salsa is a mixture of many ingredients but no matter how well mixed its never the same throughout
• Ex: sand is a mixture of various grain sizes and color
Test Your Knowledgeto the right are microscopic images of pure substances.
Are they elements, compounds, or mixtures?
1. Microscopic view of the atoms of
the element argon (gas phase). 2. Microscopic view of a gaseous
mixture containing two elements (argon and nitrogen) and a compound (water).
3. Microscopic view of the molecules of the compound water (gas phase). Oxygen atoms are red and hydrogen
atoms are white.
Meet the Elements: TMBG Video
2 Kinds of MixturesA. Heterogeneous: mixture does not appear to
be the same throughoutB. Homogenous: parts of the mixture are so
evenly distributed that they seem the sameWhat would sand be??• Heterogeneous
Reading StrategyPreviewing
Section 2.1
a. substanceb. compoundc. and d. homogeneous mixture or heterogeneous
mixture
What type of mixture are these?
• Stainless steel• Homogeneous• Mixture of iron, nickel,
and chromium
•Ocean water
•Homogenous
•Mixture of mainly water and salt but also many other elements and compounds
III. Solutions, Suspensions, and Colloids
A. Solution: a homogenous mixture that contains one or more solutions (solute) dissolved in another substance (solvent)
Ex: carbonated water = carbon dioxide and water
Solutions, Suspensions, and ColloidsB. Suspension: a heterogeneous mixture that separates
over timeEx: mud = water and fine silt or clayFilters can be use to remove the suspended materialWhat does a drink say the usually has suspended particles??“shake well before using”
Solutions, Suspensions, and ColloidsC. Colloids: in-between a solution and
suspension.• Particles usually larger than molecules but
smaller than a grain of sand• Ex: Smokes are suspensions of solid particles
in a gas. Fogs are suspensions of liquid particles in a gas
• Others: milk, mayonnaise, resin, paint, ink, expanded polystyrene, cell cytoplasm, blood serum
What are some of the Physical Properties of Matter??
• What do we mean by physical?• Some properties change in a material but the
substances remain the same• Ex: if you melt butter in a pan its still butter
just melted
Examples of Physical Properties1. Viscosity: how “thick” a
liquid ishigher viscosity = slower moving
2. Conductivity: a materials ability to allow heat to flow
• Metals are good conductors of heat
• Usually relates to electricity
Examples of Physical Properties3. Malleability: ability of a solid to be
hammered without shatteringWhat is a good malleable material?Clay, gold, silverWhat is a “brittle” solid?Ice and glass
Examples of Physical Properties4. Hardness: ability to scratch another object or
be scratched• Used to identify mineral• What is the hardest material?• Diamonds. They make the best knives !!
This knife is used to cut cells into micro-thin sections. The cost of the blade is over $5,000.
Examples of Physical Properties5. Melting and Boiling points• Only changes phase not composition• What is the only metal that it liquid at room
temperature?• Mercury
Examples of Physical Properties6. Density: mass of an
object per unit volume (D=M/V)
• Which box has the greater density?
• Can test purity b/c elements have known densities
B. Physical vs. Chemical
• Physical Property– can be observed without changing the identity of
the substance
• Chemical Property– describes the ability of a substance to undergo
changes in identity
Why Does Milk Curdle?• Milk contains many 'ingredients'. Of course
there is fat (non in 'non-fat' milk), but there are also proteins in milk. These proteins are floating around in your milk, which is a colloidal system.
When you add lemon juice (or vinegar), the water in which the proteins are floating becomes acidic and the proteins don't like this. They start to 'flock' together, because if they are curdled they have less surface which is in contact with the acidic water.
The same process, but not with lemon juice, is used when making cheese.
Cottage cheese is made by a chemical reaction.
B. Physical vs. Chemical
• Signs of a Chemical Change– change in color or odor (match turns black, copper
turns green)
– formation of a gas (backing soda and acid)
– formation of a precipitate (solid) (milk protein and acid)
– change in light or heat
B. Physical vs. Chemical
• Examples:– rusting iron
– dissolving in water
– burning a log
– melting ice
– grinding spices
chemical
physical
chemical
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