Chemistry Review Physical vs Chemical Properties Physical properties

Chemistry Review

Physical vs Chemical Properties • Physical properties describe the physical appearance and composition of a substance Ex. Boiling point, melting point, malleability, ductility, colour etc. • Chemical properties describe the ability of a substance to change into a new substance (or substances) Ex. Ability to burn, react in air or water etc.

Metals, Non-metals, Metalloids, Period, Group/Family, Alkali metals (react with oxygen and water), Alkaline earth metals, Halogens (very reactive), Noble Gases (very nonreactive)

Metals, Non-metals, Metalloids • Metals : ▫ ▫ ▫ Conduct heat and electricity Ductile Malleable Shiny, often silver Solid at room temperature (except mercury) • Non-metals: ▫ Poor conductors of heat/electricity ▫ At room temperature some are solids, some gases, and Bromine is a liquid • Metalloids: ▫ Properties are intermediate of metals and non-metals

Elements on the Periodic Table Atomic number = number of protons in an atom of an element 16 -2 S 32. 065 • Ion charge = an atom that gains electrons becomes a negatively charged ion (anion), and an atom that loses electrons becomes a positively charged ion (cation) Atomic mass = the average mass of one atom of that element

Subatomic Particles • Electrons have a charge of -1 • Neutrons have a charge of 0 • Protons have a charge of +1 • The mass of protons and the mass of neutrons is almost 2000 x the mass of electrons • PICTURE

Bohr Model of the Atom Electrons (charge of -1) surround the nucleus in shells, each shell has an energy level First, and innermost, shell has 2 electrons max Second and third shells can hold up to 8 electrons each Protons (charge of +1) and neutrons (no charge) are in the nucleus The outermost shell in an atom is the valence shell, and electrons in this level are called valence electrons

Lewis Dot Diagrams • Draw the chemical symbol with the valence electrons surrounding it • H • • C • • • N • • • F • • • Form bonds (two electrons per bond) between elements to draw the compounds

Compounds • Pure substance made up of two or more elements, where the elements are chemically combined • IONIC Formed by one or more positively charged ions and one or more negatively charged ions • MOLECULAR Formed when atoms of two or more elements combine

Ionic Compounds • Electrons are transferred between the atoms that are combining • Metal atoms tend to lose electrons, non-metal atoms tend to gain electrons • Bonded ions will now have 8 electrons in their valence shells • Name metal ion first, name non-metal ion with “ide” when it becomes a negative ion

Molecular Compounds • Atoms are joined together by bonds, formed by a single pair of electrons Other important concepts: • Polyatomic Ions • Diatomic Molecules • Chemical Formula • Chemical Name***

Chemical Reactions • Transformation of substance(s) into new substance(s) with new properties Reactants Products Law of Conservation of Mass of the reactants equals the mass of the products in a chemical reaction Exothermic Reaction = Energy is released in the form of heat, energy required is less than energy released Endothermic Reaction = Energy is absorbed in the form of heat; energy required is greater than energy released

• Word Equation vs Formula Equation

Balancing Equations • Word Equations vs. Formula equations • Start with a skeleton equation (unbalanced) • Ensure that all atoms have the same amount on both sides, by changing ONLY the coefficients (number placed in front of the element or chemical formula) Li + Al. Cl 3 Li. Cl + Al Ag. I + Fe 2(CO 3)3 Fe. I 3 + Ag 2 CO 3

Chemical Reactions Synthesis Reactions – two or more elements or compounds combine to form a more complex compound A + B AB 8 Fe + S 8 8 Fe. S 2 H 2 + O 2 2 H 2 O

Decomposition • A complex compound is broken down into two or more elements or simpler compounds AB A + B 2 H 2 O 2 H 2 + O 2

Single Displacement • One element takes the place of another element in an ionic compound A + BC AC + B 2 Ag. NO 3 + Zn 2 Ag + Zn(NO 3)2 Mg + 2 H 2 O Mg(OH)2 + H 2

Double Displacement • Positive or negative ions (cations or anions) in two dissolved compounds switch places, forming two entirely different compounds • Reactants are always compounds AB + CD AD + CB Pb(NO 3)2 + 2 KI Pb. I 2 + 2 KNO 3

Combustion • A fuel (often a hydrocarbon, Cx. Hy) reacts with enough OXYGEN to produce heat and light Cx. Hy + O 2 CO 2 + H 2 O COMPLETE combustion • A fuel reacts with less OXYGEN to produce less heat and light Cx. Hy + O 2 CO 2 + CO + C(s) + H 2 O. . . . INCOMPLETE combustion

Acids • Proton donors • Release H+ ions in aqueous solutions • High concentration of H+ ions • p. H less than 7 • Taste sour • Turn blue litmus paper re. D • Conduct electricity, dissolve in water (aqueous solution), cause skin burns or irritation

Bases • Proton acceptors • Release OH- ions in aqueous solutions • High concentration of OH- ions (low H+) • p. H greater than 7 • Taste bitter • Turn red litmus paper Blue • Conduct electricity, dissolve in water (aqueous solution), cause skin burns or irritation

p. H • Power of Hydrogen • 0 -14 scale • <7 Acidic • 7 Neutral • >7 Basic • Logarithmic scale (10 fold change per p. H unit) • p. H is tested for aqueous solutions (dissolved in water) • p. H indicators are compounds that change colour in the presence of acids or bases (ex. litmus paper, universal indicator)

Neutralization Reactions • When an acid and a base react to form a salt and water Acid + Base A salt + Water HCl + Na. OH Na. Cl + H 2 O H 2 SO 4 + NH 4 OH (NH 4)2 SO 4 + H 2 O H 2 SO 4 + 2 NH 4 OH (NH 4)2 SO 4 + 2 H 2 O