unit 2 – section a why we use what we do. hw 1 read & take notes on sections a.1 (pg. 110)...

Unit 2 – Section A

Why we Use What We Do

HW 1

Read & take notes on sections A.1 (pg . 110) & A.2 (pg. 111) , being

certain to address all the examples in section A.2

A.1 – Properties Make the Difference

Physical properties: » Color» Density» Odor

May be determined without altering chemical make-up

Ex.

2.06 g/cm38.96 g/cm

3

A.1 – Properties Make the Difference(continued)

Physical change: » Melting» Boiling» Bending

An actual physical change, material unalteredEx.


Chemical change is when a material changes into one or more new substances.


Chemical properties determine a chemical’s usefulness.

A.2 – Physical & Chemical Properties

S.P. 1: Copper compounds are often blue in color

S.P. 2: Oxygen gas supports the burning of wood

PHYSICAL PROPERTY

CHEMICAL PROPERTY

A.2 – Physical & Chemical Properties(continued)

1: Pure metals have a high luster (shiny)

2: The surface of some metals become dull when exposed to air

PHYSICAL PROPERTY CHEMICAL PROPERTY


3. N2 which is a relatively nonreactive element at room temp. , can form NO2 at high temperatures of an auto engine.

4. Milk turns sour if left too long at room temperature

CHEMICAL PROPERTY CHEMICAL PROPERTY


5. Diamonds are hard enough to be used as coating for drill bits.

6. Metals are typically ductile (can be drawn into wires)

PHYSICAL PROPERTY PHYSICAL PROPERTY


7. Leavened bread dough increases in volume if it is allowed to rise before baking.

8. Unreactive argon gas, rather than air, is used to fill many light bulbs to prevent the metal filament wire inside the bulb from being destroyed through oxidation.

CHEMICAL PROPERTY CHEMICAL PROPERTY


9. Generally, metals are better conductors of heat and electricity than are nonmetals.

CHEMICAL PROPERTY

HW 2

Read & take notes on sections A.3 & A.4.And complete the following

Element Cards

A.3 – Properties Matter: Designing the new coin…

Every element has its own physical & chemical properties.

When deciding what to use how do we decide the best substance for our needs?

1. 2. 3.

4. 5. 6.

7. 8. 9.

A.4 – The Chemical ElementsHow are chemical elements placed on the

periodic chart of elements?

A.4 – The Chemical Elements(continued)

Two major classes of elements are metals and nonmetals. Several elements have properties of both and are called metalloids.

HW 3

Pre-read section A.5

A.5 – Metal or Nonmetal?

See pgs 115 – 117

By the end of class – answer how you did on the predictions AND questions 1-4 on pg 117.

A.5 – Metal or Nonmetal? (Lab follow up)

Common lab issues:1) Make certain you answer the question being

asked.2) Restate the question in the form of a

statement and ADD your information.3) Make it a goal to show me that you have

actually thought about the question, rather than prove you never even considered it.

(example next slide)

No shoveling please . . .

Q – How did you do on your predictions? (tell me below)

Student answer:“On my predictions I made the common sense

answer but there was a few more per question and a few surprising ones but relatively well.”

As apposed to the following

Q – How did you do on your predictions? (tell me below)

Student answer:“Malleable * I got 2/4 correct. Me – Mg & Zn,

results Al, Cu , Mg ,Zn

HW 4

Pre-read and take notes on A.6And make certain you have your element

cards with you when you come to class next day.

A.6 – The Periodic Table(A Brief History)

By mid-1800s, chemists identified ~60 elements. Five were nonmetals, gasses at room temperature.

hydrogen (H)oxygen (O)nitrogen (N)

fluorine (F)

chlorine (Cl)

Two liquids were also known.

Metal : mercury (Hg)

Nonmetal : bromine (Br)

Scientist tried to place elements near one another based on similar properties.

A.6 – The Periodic Table(A Brief History)

Dimitri Mendeleev, a Russian chemist published one of the first such tables in 1869.

An offshoot is still used today based on two characteristics: 1) atomic masses and

2) combining capacity.

A.6 – The Periodic Table(continued)

A.7 – Grouping the Elements

See page 119

HW 5

Read & take notes on sections A.8

A.8 – The Pattern of Atomic Elements

Refresher : Atoms consist of sub-atomic particles

Protons , small positively charged particles and neutrons, particles with no charge make up the nucleus of an atom.

Electrons are a negatively charges particles found in varying energy levels surrounding the nucleus.

A.8 – The Pattern of Atomic Elements(continued)

The number of protons in an atom is called the atomic number. For the example to the right the value would be _____

Mass number is the total number of protons and neutrons in the nucleus of an atom. Example to the right the value would be ____


While all atoms of particular elements have the same number of protons, they contain different number of neutrons.

Example (from book) , carbon (C) always has 6 protons, but may contain 6,7, or 8 neutrons – these are called isotopes.


So why are the atomic masses we see on the periodic table not integers (whole numbers)?

They take into account the weighted average of the atomic masses of the naturally occurring isotopes.

Candium Isotopes

HW 6

Pre-read section A.9

A.9 – Periodic Variation in Properties

See pgs 122-123 Graphing lab we’ll do together.After graphing the data , please answer

questions 1,3 & 4 on pg 123

HW 7

Read & take notes on sections A.10 and answer A.11

A.10 – Organization of the Periodic Table

The table forms horizontal rows called periods.Their periodic relationship is seen in the modern table

shown below.

A.10 – Organization of the Periodic Table(continued)

Each of the columns is called a group or family, due to their similar properties


The alkali metal family is the six (6) elements in the first column starting with Lithium


The noble gas family is the six (6) elements in the rightmost column which are unreactive, chemically inert

elements.


The halogen family is the five (5) elements immediately to the left of the nobles that readily form ions.

A.11 – Predicting PropertiesUsing the periodic chart we can predict properties of the various elements.

A.11 – Predicting Properties(continued)

1) Given, the b.p. of argon (Ar) is -186°C and of xenon (Xe) is -112°C. Estimate the b.p. of krypton (Kr).

Krypton should have a boiling point between argon 87 K and xenon 161 K of about 124 K – actual = 120 K.


2a) Given, the m.p. of potassium (K) is 337°K and of cesium (Cs) is 302°K. Estimate the m.p. of rubidium (Rb).

2b) Would the m.p. of sodium (Na) be higher or lower than (Rb) , explain.

Actual = 312 K


3) Known, silicon tetrachloride exists (SiCl4) Predict the formula for Ge and Cl.

GeCl4


4) Known, the following exist : NaI, MgCl2, CaO, Al2O3, and CCl4

Predict the combination

a) C and F

CF4




b) Al and S

Al2S3




c) K and Cl

KCl




d) Ca and Br

CaBr2




e) Sr and O

SrO

HW 8

Read & take notes on sections A.12

A.12 – What Determines Properties?

Major difference between metals and nonmetals is that metal atoms lose electrons more easily.

A.12 – What Determines Properties?(continued)

Some physical properties of metals depend on attractions among their atoms. Stronger attractions = higher melting points

m.p. of Mg is 650°C

m.p. of Na is 98°C

A.12 – What Determines Properties?(continued)

Understanding properties of the chart is the key to predicting – this allows chemists to create new chemical compounds to meet specific needs.

Predicting Properties

Periodic Chart of Elements Online

Link http://www.ptable.com/

http://www.ptable.com/

http://www.ptable.com/

HW 9

See the next slide

A.13 – It’s Only Money

Address questions 1-6 on pg 127.

unit 2 – section a why we use what we do. hw 1 read & take notes on sections a.1 (pg. 110)...

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