NOTES: Elements, Compounds, and Mixtures

RECALL… MATTER: anything that has mass and occupies space

Matter Pure Substances Mixtures Elements Compounds Homogeneous Heterogeneous

PURE SUBSTANCES: A pure substance is made of only one kind of material and has definite properties. EXAMPLES: elements, compounds

What are the Differences Between an Element and a Compound? ELEMENTS – simplest form of matter that can exist under normal laboratory conditions Elements cannot be separated into simpler substances by chemical means Building blocks for all other substances Examples: nitrogen (N 2 ), hydrogen (H 2 ), and carbon (C)

ELEMENTS (continued)… The smallest particle of an element that has the properties of that element is called an ATOM.

**Currently we have about 115 kinds of atoms. In the natural world there are 88 different kinds of atoms. The others have been artificially produced in laboratories. Making stuff nature never dreamed of. The Elements Song

PERIODIC TABLE:

Abundance of the elements, by weight

The Earth’s interior is rich in IRON (Fe)

Sand is made of silicon & oxygen

The ocean waters are made of oxygen & hydrogen

Atoms are made up of protons, neutrons, and electrons. Protons and neutrons are found in the nucleus of atoms -- roughly at the center Electrons travel around the nucleus. Of course real atoms don’t look anything like this!

Different kinds of atoms, or elements, are different because they have different numbers of protons. They don’t look anything like this either!

We list the elements by their atomic numbers - the number of protons they have. Hydrogen, number 1 Helium, number 2

COMPOUNDS COMPOUNDS = pure substances that can be separated into simpler substances only by chemical means made of more than one element bound together Examples: water, table salt, and carbon dioxide

sodium (Na) chlorine (Cl)Sodium chloride (NaCl)

CHEMICAL SYMBOLS: CHEMICAL SYMBOL – one or two letter symbol representing an element on the periodic table First letter is always capitalized Second letter is always lower case Examples: sodium – Naiodine – I lead – Pb iron – Fenickel – Ni

CHEMICAL FORMULAS: Chemical formulas: Chemical symbols and numbers indicating the type and number of atoms contained in the basic unit of a substance. Examples: water – H 2 O sodium chloride – NaCl sucrose – C 12 H 22 O 11

Chemical Formulas… C 16 H 10 N 2 O 2 Carbon # of Carbon atoms 2 Oxygen atoms

CaCl 2 No subscript because there’s only 1 calcium atom How many chlorine atoms? Interpreting Chemical Formulas…

CaCl 2 No subscript because there’s only 1 calcium atom How many chlorine atoms? 2 Interpreting Chemical Formulas…

5 H 2 O 5 molecules of H 2 O How many hydrogen atoms? How many oxygen atoms? Interpreting Chemical Formulas…

5 H 2 O 5 molecules of H 2 O How many hydrogen atoms? 10 How many oxygen atoms? 5 Interpreting Chemical Formulas…

3 (NH 4 ) 3 PO 4 3 molecules of (NH 4 ) 3 PO 4 How many hydrogen atoms? How many nitrogen atoms? How many oxygen atoms? Interpreting Chemical Formulas…

3 (NH 4 ) 3 PO 4 3 molecules of (NH 4 ) 3 PO 4 How many hydrogen atoms? 36 How many nitrogen atoms? 9 How many oxygen atoms? 12 Interpreting Chemical Formulas…

Matter Pure Substances Mixtures Elements Compounds Homogeneous Heterogeneous

MIXTURES: MIXTURE = physical blend of two or more substances (that are NOT chemically combined) can be classified as: HOMOGENEOUS or HETEROGENEOUS

Homogeneous Mixture Uniform in composition; Exhibits identical properties throughout the mixture; Examples: air, salt water, soda water, solutions, whipped cream, mixture consisting of one phase

Heterogeneous Mixture Not uniform in composition; Exhibits portions with different properties; Examples: salad, sand, muddy water, oil and water, soup, granite, soil, mixture consisting of two or more phases, etc.

How are Mixtures Separated? Many mixtures can be separated by simple PHYSICAL means: Boiling point differences Melting point differences Particle size Density Magnetism Solubility Color Smell