Accelerated Science Properties of Matter

Properties of Matter I.Pure Substance: matter that always has the same composition EX: table salt (NaCl) is a pure substance b/c it is equally as salty throughout 2 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 (H 2 0) 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 Knowledge to 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 Mixtures A.Heterogeneous: mixture does not appear to be the same throughout B.Homogenous: parts of the mixture are so evenly distributed that they seem the same What would sand be?? Heterogeneous

Reading Strategy Previewing Section 2.1 a.substance b.compound c. 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 Colloids B. Suspension: a heterogeneous mixture that separates over time Ex: mud = water and fine silt or clay Filters can be use to remove the suspended material What does a drink say the usually has suspended particles?? “shake well before using”

Solutions, Suspensions, and Colloids C. 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 Properties 1.Viscosity: how “thick” a liquid is higher 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 Properties 3. Malleability: ability of a solid to be hammered without shattering What is a good malleable material? Clay, gold, silver What is a “brittle” solid? Ice and glass

Examples of Physical Properties 4. 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 Properties 5. Melting and Boiling points Only changes phase not composition What is the only metal that it liquid at room temperature? Mercury

Examples of Physical Properties 6. 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 physical