Basic Concepts About Matter

Chemistry and Matter Matter - anything that has mass and takes up space (has volume) What are some examples? Chemistry – the study of matter and the changes it undergoes What types of chemists are there?

Three phases (states) of matter What are the three phases of matter? How do they compare in terms of shape, volume, and compressibility?

Physical and Chemical Properties Physical property – can be observed without changing the identity of the substance What are some examples? Chemical property – describes how a substance undergoes (or resists) change (chemically reacts) to form new substances

Physical and chemical changes Physical change – substance changes in appearance but its identity is not changed What are some examples? Chemical change – substance changes (chemically reacts) in a way that changes its chemical composition and therefore changes its identity

Properties and Changes

Pure substances and mixtures Pure substance – can not be separated into simpler substances by physical means (as opposed to chemical reactions that break chemical “bonds”) Mixture – two or more pure substances mingled in a way where each retains its own identity

Pure substances Element: Pure substance that cannot be broken down into simpler substances by chemical means (breaking bonds) 115 known Compound: Pure substance made up of two or more elements chemically combined. Can be broken down into those elements by chemical means. 9 million known

Mixtures Homogeneous: Has one visible phase Has the same composition throughout Examples? Heterogeneous: Has two or more visible phases Has a different composition when sampled in different areas

Relative abundance of elements

Common elements and polyatomic ions The first three periods Family IA (the first six elements) Family IIA (the first five elements) Family VIIA (the first five elements) The following elements: Cr, Mn, Fe, Co, Ni, Cu, Zn, Ag, Sn, Au, Pb, Hg Know the following polyatomic ions: NH4+ (ammonium ion), OH- (hydroxide ion), NO3- (nitrate ion), NO2- (nitrite ion), SO32- (sulfite ion), SO42- (sulfate ion), PO43- (phosphate ion), CO32- (carbonate ion), HCO3- (bicarbonate ion)

Atoms, molecules and compounds Atom: smallest particle of an element that still has the properties of that element Molecule: two or more atoms chemically combined Compound: two or more atoms from different elements that are chemically combined

Different types of molecules

Classify these as: a) diatomic, triatomic, etc… b) homoatomic or heteroatomic c) elemental or compound

Chemical formulae Tells you what elements are present in a molecule and the number of atoms of each type of element Molecular formula: Tells you the elements and the actual number of each atom within the true molecule Empirical formula: Tells you the elements and the lowest whole number ratio of each type of atom