Chemistry TAKS Review Fast Track

Density Density = mass volume D = M V

Math Tip for Density D =M V1 Cross Multiply

Buoyancy

The force that acts on objects immersed in or floating on a liquid Photo from:

Buoyancy Buoyancy is related to floating an object in a liquid is buoyed up (pushed up) by a force equal to the weight of the liquid the object displaces (pushes aside). This is known as Archimedes’ Principle. Photo from:

Viscosity

Viscosity is the resistance of a liquid to flow If a liquid flows slow, it is viscous, or has a high viscosity

Objective 4 - (I.7D)

Periodic Table of the Elements An organized table of all the known elements

Atomic Number = Number of Protons

Groups vertical columns contains elements with similar chemical properties EX: Li, Na, K

Periods horizontal rows EX: K, Ca, Sc

Staircase = Metalloids (metal/non-metal combo) Right side + Hydrogen = Non-metals Left side = Metals

Transition Metals Groups 3-12 are called transition metals

Alkali Metals Group 1 (IA) Very reactive

Valence Electron: Outer Electron Na

Number of valence electrons represented by the roman numerals

Note this on your periodic table Valence electrons

Every element wants 8 valence electrons to be stable Elements will lose or gain electrons (which ever is easier) to become stable

Predict if an element will lose or gain electrons? How many?

Charges When electrons are gained or lost, a charge is formed Na 1+

Note this on your periodic table Charges

Noble Gases Group 18 (8A) Very stable & will not lose or gain electrons Unreactive

Writing Formulas

To make an ionic compound, the charges must cancel out Charges

Goal: Cancel out the charges Example: Magnesium + bromine Mg +2 Br - I need two bromines to cancel out with 1 Mg +- MgBr 2

Br Criss Cross Method Mg

Criss Cross Method MgBr 2

Criss Cross Method Al SO 4

Criss Cross Method Al 2 SO 4 3 ()

Al 2 (SO 4 ) 3 Al o o S o o o o s o o o o s o o SO 4

Physical Changes More Examples –Cutting –Breaking apart

Law of Conservation of Mass Mass can not be created or destroyed

Using the Law of Conservation of mass 2H 2 + O 2  2H 2 O H 2 O(s)  H 2 O(l) C + O 2  CO grams50 grams? 150 grams 32 grams 60 grams20 grams? 40 grams

Balancing Equations

A reaction must be balanced to obey the law of conservation of mass Non-balanced Reaction H 2 + O 2  H 2 O Balanced Reaction 2H 2 + O 2  2H 2 O

How to balance a reaction Step one: list all the element symbols under the arrow of a reaction H 2 + O 2  H 2 O H O

How to balance a reaction Step two: count how many of each atom you have on each side of the reaction H 2 + O 2  H 2 O H O 22 21

Coefficients Numbers that are placed in front of a compound/molecules in a reaction

How to balance a reaction Step three: add coefficients to the compounds to help make each element even on both sides H 2 + O 2  H 2 O H O

The reaction H 2 + O 2  H 2 O 2 2

21 Balance Me! ___ XeF 2 + ___ H 2 O  __ Xe + __ O 2 + __ HF Xe F H O

Ions in solution Objective 4: IPC 9B TSW relate the concentration of ions in a solution to physical and chemical properties such as pH, electrolytic behavior, and reactivity

Distilled water is pure water. It has no ions in it at all. An ion is any substance that has a charge. A charge is indicated by a + or - sign. Ions in solution (dissolved minerals) can conduct electricity.

Litmus Paper Aciase Relue B D

More solute will result in a boiling point elevation (increase) and freezing point depression (decrease) Why do people put salt on icy roads?