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

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