Matter

PureSubstances

Mixtures

Mechanical Mixtures

Solutions Compounds Elements

Chemistry is the study of matter, its properties and its changes or transformations.

Matter is something that has mass and occupies space (has volume).

A pure substance is a kind of matter that cannot be separated into other kinds of matter by any physical process.

A mixture is a composition of two or more pure substances (not chemically bonded) with each other and are capable of being separated.

An element is a substance (homogenous) made up of one type of atom.

A compound is a substance (homogenous) made up of one type of molecule or formula unit.

A solution (homogenous mixture) is a mixture that displays one phase.

A mechanical mixture (heterogeneous mixture) is a mixture that’s displays two or more phases.

Examples

Elements:

Compounds:

Solutions:

Mechanical Mixtures:

Solutions and Mechanical Mixtures can be hard to distinguish. Liquid or gaseous solutions are transparent while mechanical mixtures are not (display the Tyndall effect).

(air, pop, hydrogen in Pt, sea water, gasoline, dental amalgams (Hg in Ag), Brass (Cu, Zn), Bronze (Cu, Sn), solder (Sn, Pb)) (Suspensions: penicillin, Peptobismol, Milk of Magnesia, salad dressing, milk, paint colloids: whipped cream, shaving cream, )

Solutions are made up of a solvent which is the substance that dissolves one or more solutes. A solution retains properties from the solute and the solvent.

Mechanical mixtures are heterogeneous which means that you can see the different particles in them (two or more phases). Two types of these mixtures seem homogenous but upon closer inspection are not. In a suspension the particles may be seen with the unaided eye or through a microscope. Over time gravity will cause the suspended particles to separate. If the suspended particles are small enough gravity will not cause the particles to separate. This type of mixture is a colloid.

Mixtures are separated by physical means such as evaporation, distillation, freezing, filtration, flotation). Elements can only be broken down by nuclear reactions while compounds can only be broken down by chemical reactions)

States of Matter

There are three states of matter: solid, liquid and gas.

Please sketch 20 water molecules in the ice form in a beaker. Next sketch 20 water molecules in the liquid form in a different beaker. Finally repeat this sketch for 20 molecules of water in the steam form.

Matter Drawings

Sketch 20 solid iron atoms. Sketch a solution of 20 water molecules and 10 sugar molecules. Sketch a mechanical mixture of 20 water molecules and 20 oil molecules before and after shaking.

Physical Properties

A property is a quality or characteristic. - a diamond is hard- iron rusts

The physical properties of a substance are those properties which can be determined without changing its composition or make-up. Physical properties include colour, odour, length, area, volume, mass, hardness, melting and boiling point, conductivity, solubility, and density.

Mercury is an odourless liquid with a silvery shine. It does not dissolve in water. It is an excellent conductor of electricity. It freezes at -39o C and boils at 357o C.

Chemical Properties

The chemical properties of a substance are those properties which can be determined only when a substance undergoes a change in composition (chemical reaction).

Gold is difficult to distinguish from fool’s gold. Fool’s gold reacts with nitric acid while gold does not. Carbon burns in air to produce carbon monoxide and carbon dioxide. Carbonic acid decomposes into water and carbon dioxide.

A substances reactivity can be broken down into a few areas. Reactivity with other substances, combustibility, stability and toxicity are some of these areas.

Quantitative and Qualitative Properties

A quantitative property is one that can be measured. Numbers will be used in expressing a quantitative property.

Qualitative properties are those which cannot be expressed numerically. Examples include appearance and odour.

Physical Change

A physical change is a change which alters one or more properties of the substance with no change in its composition or identity.

-freezing, melting, boiling, condensing, evaporation, sublimation, breaking, tearing, bending, flattening

What properties of the substance change in the following physical changes: melting, boiling, breaking, bending?

Chemical Change

A chemical change is a change in a substance which converts it into a different kind (or different kinds) of matter (each with a different composition and new properties).

PENPEN

location charge massproton nucleus +1 1 uelectron orbit -1 0 uneutron nucleus 0 1 u

an electron actually weight 1/1876 u but we treat this as 0 u for our purposes

X is the element symbolA is the atomic mass in atomic mass units (u)Z is the atomic number (number of protons)b is the electric charge c is the number of atomsRemember these simple rules for analyzing elements.

#p+ + #e- = b

#p+ + #no = A

bc

AZ X

B115

Hydrogen deuterium tritium

-only hydrogen has names for its isotopes

Mg2412 Mg25

12Mg26

12

F199 Si28

14 U23892

H11 H21 H31

2126

C 33717

Cl Au19779

6 p+, 4e-, 6no 17 p+, 20e- , 20no79 p+, 78e- , 118no

-try the PEN sheet -the # of p+ determines which element it is

Average Atomic Mass

Naturally occurring elements are made up of different isotopes. The mass of an element found on a periodic table is the average atomic mass. It can be calculated by a weighted average of the isotope masses and their percentage natural occurrence.

%7.78

2412Mg

%13.10

2512Mg

%17.11

2612Mg

uAverage

Average

32.24

)1117.0(26)1013.0(25)787.0(24

These calculations may not agree exactly with the average atomic mass on the periodic table because the isotope masses above are not exact. When making an atom from protons and neutrons mass is lost in the fusion or fission reaction.

The Periodic Table

The Periodic Table has gone through many forms to its present day arrangement. Today the only changes that are possible for the future are the addition of more elements.

There are various levels of organization in the Periodic Table of your textbook. Try and answer these questions to discern this organization.

How are gaseous, liquid and solid elements displayed?

How are metals, non-metals and metalloids displayed.

The highlight of the Periodic Table is the organization of elements in families or groups (vertical columns). These families have similar Lewis Dot diagrams and display similar chemical properties.

Lewis Dot DiagramsIn some ways chemistry can be thought of as how atoms interact with other atoms. The outer shell electrons or valence electrons are the most important part of this interaction. Lewis Dot Diagrams show the valence electrons of an atom. The pattern of valence electrons is the fundamental pattern that determines chemical reactivity.

H He

Li Be B C N O F Ne

Na Mg Al Si P S Cl Ar

The fourth period is 18 elements wide however the patterns set up in the second and third rows continue for the rest of the periodic table. The transition metal electrons do enter the outer shell but drop down a level upon leaving the transition metal area. The loss of these ten electrons means that once again the inert gases need eight electrons in their outer shell. Lewis Dot Diagrams are not drawn for transition metal elements.

K Ca Ga Ge As Se Br Kr

Rb Sr In Sn Sb Te I Xe

Ions

An ion is an electrically charged atom or group of atoms. Atoms lose or gain electrons to have a full outer shell. They become isoelectronic with the nearest Noble gas. This full outer shell is a more stable arrangement than the neutral atom. Noble gases do not form ions because they are already quite stable with a full outer shell.

Every atom has two choices (full or empty) but the choice which involves gaining or losing the least electrons forms the preferred ion.

Hydrogen can lose or gain one electron to become stable (H+ or H-) however the positive hydrogen ion (p+ or H+) is much more common.

Carbon and all other members in its group can lose or gain four electrons to become stable, however since this involves so many electrons neither positive or negative ion is common.

F- Cl- Br- I- At-

Li+ Na+K+ Rb+ Cs+

Be+2 Mg+2 Ca+2 Sr+2 Ba+2

B+3 Al+3 Ga+3 In+3 Tl+3

O-2 S-2 Se-2 Te-2 Po-2

N-3 P-3 As-3 Sb-3 Bi-3

Separating mixtures, conservation of mass, constant composition, evidence of chemical change