Honors Chemistry 1st Semester Review

Scientific Method - Observe• Observation – the receiving knowledge or

data through the senses, or from scientific instruments

• Inferences – Assumptions based on observations.

• Example:– Observation: Car won’t start in the morning.– What would you assume (or infer) the problem is?

Scientific Method - ObserveObservations:• 1. Qualitative

– Do you like this powerpoint?• Usually uses the five senses.

• 2. Quantitative– How many words are on this

powerpoint?• Usually can be answered precisely.

Scientific Method - Hypothesis

Hypothesis : a statement that answers a question

(a possible explanation)

Tells what are the independent and dependent variables and how to measure

them.

How do Scientists Communicate? By sharing information.-Poster sessions-Presentations at conferences/meetings-Scientific Journals-Shared Data Bases - Internet

What happens when scientists disagree?Scientific arguments are solved through further observation and experimentation

To reveal data trends, data is placed in graphs

Time (min)

Temp. (˚C)

0 01 02 03 54 105 156 207 258 259 30

10 30

Temperature Change over Time

05

101520253035

0 1 2 3 4 5 6 7 8 9 10

Time (min)

Tem

p (

C)

Finding Volume of Irregularly shaped items

This is called Water Displacement

The Graduated CylinderMeasures Volume

Start by locating the meniscus

Always make your reading at the bottom of the meniscus!!

Finding Density

Density is a ratio between mass and volume.

You need to divide to find the ratio. Density = mass divided by volume

OR D = M/V

Electronic BalanceMeasures Mass

Turn balance on Make sure it reads “0” Place item on balance Obtain mass Turn balance off

SI Unit for mass is the kg

SyllabusWhat is Chemistry?

Chemistry is the study of matter and energy and the interactions between them.

Chlorine – gas will kill you

Sodium – metal reacts violently with oxygenIt is stored in oil.

Sodium + Chlorine= Table Salt which our bodies need

Pure vs. Applied Science• BOTTOM LINE:

• Pure Science is just for the knowledge.

• Applied Science is for someone to make money off of the invention (new technology)

What IS science based on?

•Experimentation

•Observation

Rules for significant figures:

(1) All nonzero digits are significant (1-9):1.234 g has 4 significant figures1.2 g has 2 significant figures

(2) Zeroes between nonzero digits are significant:1002 kg has 4 significant figures3.07 mL has 3 significant figures

(3) Leading zeros (left) of the first nonzero digits are NOT significant; They indicate the position of the decimal point:

0.001°C has only 1 significant figure0.012 g has 2 significant figures

(4) Trailing zeroes (after a decimal point) are significant:

0.0230 mL has 3 significant figures,0.20 g has 2 significant figures.

(5) When a number ends in zeroes that are not to the right of a decimal point, the zeroes are not necessarily significant:

190 miles may be 2 or 3 significant figures50,600 calories may be 3, 4, or 5 sig figures

• The potential ambiguity in the last rule can be avoided by the use of standard exponential, or "scientific," notation.

• What is an "exact number"?

• Some numbers are exact because they are known with complete certainty.

• Most exact numbers are integers: exactly 12 inches are in a foot, there might be exactly 23 students in a class.

• Exact numbers are considered to have an infinite number of significant figures.

• Rules for mathematical operations• In calculations, the general rule is that the accuracy of a calculated

result is limited by the least accurate measurement involved

1) In addition and subtraction, the result is rounded off so that it has the same number of digits as the measurement having the fewest decimal places (counting from left to right). For example,

101 (3 sig figures) + 23.643 (5 sig figures) = 124.643, which should be rounded to 125 (3 sig figures).

302.1 + 54.345 = 356.445,which should be rounded to 356.4 (least shared decimal place)

2) In multiplication and division, the result should be rounded off so as to have the same number of significant figures as in the component with the least number of significant figures. For example,

3.0 (2 sig figures ) × 12.60 (4 sig figures) = 37.8000

which should be rounded to 38 (2 sig figures).

Temperature

Converting between ºC and K

Example

Practice

• ºC = K – 273• K = ºC + 273

• Normal human body temperature is 37 ºC. What is your temperature in K?

• Surgical instruments must be sterilized at 170 ºC. What is this in K?

Physical and Chemical Changes

Physical Changes: Do not alter the identity of a substance

Crushing, tearing, changes of state (solid to liquid to gas)

Chemical Changes: Alter the identity or chemistry of a substance

Burning, cooking, rusting

What is Matter?

Matter is anything that has mass and volume

States of Matter

Liquid has undefined shape but defined

volume

Pure Substances – Element Matter that can not be broken down into

simpler substances under normal lab conditions

Contains only one kind of atom Atom Molecule

Elements (symbols) Na, Au, C Where can you find a list of all the

elements?

Mixtures: Homogeneous Mixture with no visibly different

parts. Sea water - H2O + NaCl Air - N2 + O2 + CO2

Physical and Chemical Changes

Is this a physical or a chemical change? Explain your reasoning.

New substances formwhen there is a chemical change.

ATOMIC THEORIES J.J. Thomson 1897 Experiment - discovered electrons

Atom is made up of charged matter

ATOMIC THEORIES Ernest Rutherford: 1910 – Planetary Model Atom is mostly empty space Found the nucleus (a small dense region of positively

charged particles).

If the nucleus were the size of a marble, Then the atom would be the size of Cardinal’s stadium Theorized about the neutron – not proven until 1932

RUTHERFORD – GOLD FOIL EXPERIMENT DISCOVERED THE NUCLEUS

ATOMIC THEORIES John Dalton – 1808

Atomic Theory:1. Elements are made up of tiny particles called atoms.2. Atoms of one element are identical.3. Atoms of other elements are different from each other.4. Atoms can combine to form compounds.5 Atoms are not created, nor destroyed, but can change they way they are grouped together.

Periodic Table Trends The most important difference

between Mendeleev's table and today’s table:

the modern table is organized by increasing atomic number, not increasing atomic weight.

Why was the table changed? Discovery of isotopes and ions.

PERIODIC TABLEAtomic Number = Number of Protons

Hydrogen – 1 proton = #1 Helium – 2 protons = #2 Gold – 79 protons = #79

Rules: All elements on the period table are neutral.

Therefore, #of protons = #of electrons What about neutrons – we’re coming to that

later

Periodic Table Trends Groups – Columns

Elements within a group share several common properties.

Groups have the same outer electron arrangement.

Like families, the share the same characteristics

Periodic Table Trends Metals Most of the elements are metals. You see metals every day. Aluminum

foil, gold, silver. If someone asks you whether an element is a metal, metalloid, or non-metal and you don't know the answer, guess that it's a metal.

Properties of Metals lustrous (shiny) malleable (can be hammered) good conductors of heat and electricity

Periodic Table Trends Group 18: Noble Gases Helium and neon are examples of noble

gases. These elements are used to make

lighted signs, refrigerants, and lasers. The noble gases are not reactive.

He Never Argued with Superman Xenon’s a Nurse.

Periodic Table Trends Group 17: Halogens (Examples of halogens are

chlorine and iodine.) You find these elements in

bleaches, disinfectants, and salts. highly reactive.

What does this mean and why do we care?

Properties of atoms correlate with the number and energy of electrons

Atoms like to have full outer shells

Valence electrons have the most energy (this is where all the action occurs)

This will help us predict what reactions may occur when we start mixing elements together

Note periodicity of charges

Main Group Elements & Their Ions

Periodic Table – Long Form

PERIODIC TABLE Atomic # = # of Protons Symbol

Atomic Mass

PERIODIC TABLEIsotopes: elements with a different number of neutrons.

Elements have to have the same number of protons to be the same element.

ATOMIC THEORIES Mass Number

ProtonsNeutrons

NOT Electrons(too small to want to count)

PERIODIC TABLE Atomic mass

Review: What does one proton weigh? 1 atomic mass unit (amu) What does one neutron weigh? 1 amu What does one electron weigh? So small we will consider it to be zero

PERIODIC TABLE Atomic # = # of Protons Symbol

What is this?

PERIODIC TABLE Why the weird number?

We know that Lithium has 3 protons 3 amu We assume it has 3 neutrons 3 amu We assume the electrons are zero mass. So we total 6 amu. Where is the 0.941

coming from? Isotopes 6.941 is the average of all the naturally

occurring isotopes of lithium.

ELECTRON CONFIGURATION

Li-, Mg 2- Cu2+, F+

Note periodicity of charges

Main Group Elements & Their Ions

PERIODIC TABLEIsotopes: elements with a different number of neutrons.

How do we write isotopes? 14C

Alka

liAl

kalin

e Ea

rth

Transition Metals

Chal

coge

nsHa

loge

nsNo

ble

Gase

s

Periodic Table Trends Nonmetals upper right side of the periodic

table (Yellow) The halogens, the noble

gases, and the rest. Poor conductors of heat and

electricity. Solid nonmetals are brittle and

lack metallic luster.

Hund’s Rule: electrons will not share an orbit until needed

White Board PracticeLewis Symbols or Lewis Dot Diagrams• We place the electrons on four sides of a

square around the element symbol.

Practice:O Na Ca Ba

Ne H I Cs

• Check with your partner

Shorthand If it is in a row past a noble gas,

we can use that for a shortcut.

Short-hand Notation[Ne] 3s1

[Ar] 4s2, 3d1

[He] 2s2, 2p5

Energy NotesEnergy – Capacity to do work or produce

heat

– Capacity to move or change matter

Types of Energy• Stored

– Energy of position (water wheel, book on shelf)– Chemical energy (gas, food, batteries)

• Motion– Mechanical energy (moving parts of

machines)– Sound: vibration of molecules

• Radiant (EMR)Thermal energy (Sun’s heat)

Light

Potential

Kinetic

ENERGY• Energy can be converted from one form to another.

• Law of Conservation of Energy:

• energy is not created nor destroyed, but can CHANGE from one form to another.

• 3 examples of Chemical Energy.

ROYGBIV – backwards – R least energy

Wednesday – October 24• Rube Goldberg Poster –

Presentations

How do atoms release energy?Energy In Energy Out

Heat and TemperatureExothermi

c

Endothermic

• System that releases energy into its surroundings

• Release energy because a change has occurred

• Combustion reactions

• System that takes energy in as heat from the surroundings

• Needs energy from outside source in order for a change to occur

• Changing water to steam Or melting ice

How do we measure energy?

SI Unit: Joule (J)

1 Calorie = amount of energy required to raise 1g of water by 1°C

1000cal = 1 kilocalorie = 1Cal = food Calories

Conversion Factor1 calorie = 4.184 Joules

Calculating Energy

Specific Heat Capacity or Specific Heat:The amount of energy required to change the temperature of 1 g of substance by 1̊CUnits are: J (Joule) g ̊C Centrigrade NOT Calories

It takes different amounts of energy to heat different substances.

Phase Diagram - Overview

Phase Change diagram

sublimationdeposition

ExothermicEndothermic What definition are we missing?

Q= mCT• Example

4

• Practice 4

• What is the specific heat of lead if a 30.0 g piece of lead undergoes a 250ºC change while absorbing 229.5 calories?

• 0.0306 cal/gºC = sigfigs? • 3.06x10-2 cal/gºC• What is the specific heat of

an unknown substance if the addition of 950 J of heat energy caused a 20 gram sample to warm from 18ºC to 42ºC?

1.97 cal/gºC = sigfigs? 2.0 cal/gºC

Writing Formulas for Ionic Compounds• Crisscros

s Method

• Example

• Write the element symbols for the cation and anion, with the cation on the left and the anion on the right.

• Write each ion’s charge as a superscript.

• Crisscross the two charges moving them downward diagonally from one superscript to the other subscript.

Naming Binary Ionic CompoundsName Formula

Example:Calcium ChlorideCa +2 and Cl -1

CaCl2

1. Identify the ions involved2. List the cation first and

then the anion3. Determine that charge of

each ion involved4. Balance the charges so

the compound is neutral.

Naming Binary Covalent Compounds

Prefixes 1= mono (can be omitted – assumed)2= di3 = tri4 = tetra5 = penta6 = hexa7 = hepta8 = octa9 = nona10 = deca

Naming Binary Covalent Compounds

PracticeName Formula

What is the formula for the following compounds?

1. Write the chemical formula of the first element listed.

2. Write the prefix number as a subscript.

3. Write the chemical formula of the second element listed.

4. Write the prefix number as a subscript.

a. Pentachlorine dioxideb. Carbon monoxidec. Tribromine hexasulfide

Naming Binary Covalent Compounds

PracticeFormulaName

What is the name of the following compounds?

1. Write the number of the first element as a prefix, add the name of chemical.

2. Write the number of the second element as a prefix, add the name of chemical and end in –ide.

a. P4C8

b. F9I6

c. SN3

• Solids are usually soft• low melting points• low boiling points• Properties arise because molecules are

not strongly held together• Usually found with nonmetals

Properties of Covalent Bonds

• Ionic bonds are very strong (separating ions requires lots of energy)

• High melting points, boiling points• Crystals are hard and brittle• Electrical insulators when solid, electrical

conductors when molten or dissolved in water• Between a metal and a non-metal

Properties of Ionic Bonds

Why do atoms form bonds?Octet Rule

Lewis Dot Diagrams

Atoms tend to gain, lose, or share electrons in order to acquire a full set of valence electrons.

• Used to illustrate valence electrons

• Used to illustrate how electrons rearrange during chemical reactions (when bonds are formed or broken)

Review: Ions • What are Ions?• Ions are formed by adding or subtracting electrons

from a neutral atom or molecule.

Cation: positive charge Anion: negative charge (remove electrons) Na+ (add electrons) Cl-

Naming Binary Covalent Compounds

PracticeFormulaName

What is the name of the following compounds?

1. Write the number of the first element as a prefix, add the name of chemical.

2. Write the number of the second element as a prefix, add the name of chemical and end in –ide.

a. P4C8

b. F9I6

c. SN3

ORGANIC • In Chemistry, Organic means it has a carbon atom in it.

• Question: can there be an organic ion? NO – carbon does not form ions.• Can there be organic covalent bonds? YES – all carbon bonds will be covalent and therefore they will be organic.

Carbonated Drinks

• Carbonate: special group of polyatomic ion• CO3

2-

• What kind of Ion does • It need to balance?• 2+ like what family?• Alkaline Earth Metals• How many Carbon molecules? 1