Chemistry TAKS Review

Fast Track

Density

Density = mass volume

D = M V

Math Tip for Density

D =

M V 1

Cross Multiply

Buoyancy

Buoyancy

• The force that acts on objects immersed in or floating on a liquid

Photo from: http://www.seed.slb.com/en/scictr/watch/bathroom/duck.htm

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: http://www.seed.slb.com/en/scictr/watch/bathroom/duck.htm

Viscosity

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

Na1+

Note this on your periodic table

1+

2+ 3-3+

0

2- 1-

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

1+

2+ 3-3+

0

2- 1-

Charges

Goal: Cancel out the charges

Example:Magnesium + bromine

Mg+2 Br-

I need two bromines to cancel out with 1 Mg

+ -+ -

MgBr2

Br

Criss Cross Method

2 1+ -Mg

Criss Cross Method

MgBr2

Criss Cross Method

3 2+ -Al SO4

Criss Cross Method

Al2 SO4 3( )

Al2(SO4)3

AlAl

o

o

So

o

o

os

oo

o

o

s

o

o

SO4

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

2H2 + O2 2H2O

H2O(s) H2O(l)

C + O2 CO2

100 grams 50 grams ?150 grams

32 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

H2 + O2 H2O

• Balanced Reaction

2H2 + O2 2H2O

How to balance a reaction

• Step one: list all the element symbols under the arrow of a reaction

H2 + O2 H2O

HO

How to balance a reaction

• Step two: count how many of each atom you have on each side of the reaction

H2 + O2 H2O

HO

2 22 1

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

H2 + O2 H2O

HO

2 22 1

42

422

The reaction

H2 + O2 H2O22

2 1

Balance Me!

___ XeF2 + ___ H2O __ Xe + __ O2 + __ HF

XeF

1 12 14

2

2

24 H

O1 2

2

2

22

22

4

4

4

Ions

in solution

Objective 4: IPC 9BTSW 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

Aci ase Re lueBD

• More solute will result in a boiling point elevation (increase) and freezing point depression (decrease)

• Why do people put salt on icy roads?