Transcript Chem TAKS Review (Exit Level Objective 4 from Ferrer

Chemistry TAKS Review
Fast Track
Density
Density = mass
volume
D=M
V
Math Tip for Density
D= M
1 V
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
1+
Na
Note this on your periodic table
1+
0
Charges
2+
3+
3-
2-
1-
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+
0
Charges
2+
3+
3-
2-
1-
Goal: Cancel out the
charges
Example:
Magnesium + bromine
Mg+2
Br-
I need two bromines to cancel out with 1 Mg
+
+
MgBr2
-
Criss Cross Method
Mg
+2
Br
-1
Criss Cross Method
MgBr2
Criss Cross Method
Al
+3
-2
SO4
Criss Cross Method
Al2(SO4)3
Al2(SO4)3
SO4
Al
Al
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
100 grams
50 grams
?
150 grams
H2O(s)  H2O(l)
32 grams
32 grams
C + O2  CO2
20 grams
?
40 grams
60 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
H
O
How to balance a reaction
• Step two: count how many of each atom
you have on each side of the reaction
H2 + O2  H2O
2
2
H 2
O 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
2 H2 + O2  2 H2O
4 2 H 2 4
2 O 1 2
The reaction
2 H2 + O2  2H2O
Balance Me!
2
2
2
4
4
2
24
2
Xe 1 2
F 1 2 4
H1 2 4
O2
___ XeF2 + ___ H2O  __ Xe + __ O2 + __ HF
1
2
2
1
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
Aci
Re
D
ase
lue
B
• More solute will result in a boiling point
elevation (increase) and freezing point
depression (decrease)
• Why do people put salt on icy roads?