Unit 1, Section 2 - PBworksmrswhittsweb.pbworks.com/w/file/fetch/113848606/Unit 1 L6-10.pdf ·...
Transcript of Unit 1, Section 2 - PBworksmrswhittsweb.pbworks.com/w/file/fetch/113848606/Unit 1 L6-10.pdf ·...
*Basic Building Materials
Unit 1, Section 2
* Lesson 6 A New Language
* Lesson 7 Now You See It
* Lesson 8 What Goes
Around Comes Around
* Lesson 9 Create a Table
* Lesson 10 Breaking the
Code
*Lesson 6: A New
Language
You will be able to:
• define new terms
• recognize whether a substance is
an element or a compound based
on its chemical formula or symbol
• decipher some basic chemical
formulas and symbols
*vocabulary
* Element
* Compound
* Aqueous
* Chemical formula
*Key Question
* What do chemical names, formulas and
symbols tell you about matter?
Au
Do you think both these bottles contain gold?
*Can we see patterns in chemical
formulas and their compounds?
All matter in the universe either is an element ,or is made of some combination of elements.
Element: A unique substance that cannot be broken down into simpler substances through chemical processes. Elements serve as the building materials of all matter.
There are approximately 118 known elements
which are organized in the Periodic Table
based on some of their properties.
An element is represented by a symbol.
The first letter of an element’s symbol is always
uppercase and if there is a second letter it is
always lowercase.
Compound: A pure substance that is a chemical combination of two or more elements in a fixed ratio.
Compounds are
represented by
chemical formulas
which are a
combination of
symbols and
subscripts that indicate
the number and types
of elements in the
compound.
*Chemical formula for copper sulfate
Symbol for sulfur
Symbol for oxygen
Subscript for # of
oxygen atoms
Symbol for copper
CuSO4(aq)
Chemical formulas indicate the number and types of
elements in the compound.
Compounds (therefore chemical formulas) are “fixed”.
Some common groupings of elements have their own specific names.
OH hydroxide
NO3 nitrate
SO4 sulfate
SO3 sulfite
Substances come in different physical forms, called phases.
In chemistry it is common to include the phase of the compound with its formula.
Phase: The physical form a substance is in, such as solid, liquid, or gas. Phase is greatly influenced by temperature.
Aqueous: A substance is aqueous when it is dissolved in water.
Remember: “liquid” is a phase
Sodium nitrate NaNO3(aq)
Copper II nitrate Cu(NO3) 2 (s)
Nitric acid HNO3(aq)
water H2O(l)
copper Cu(s)
Sodium hydroxide NaOH(s)
Sodium hydroxide NaOH(aq)
*summary * What do chemical names and symbols tell you
about matter?
* Chemical symbols represent the elements. Each element has either a one- or two-letter symbol. The first letter is always uppercase; the second letter is always lowercase.
* The chemical formula of a substance indicates what elements are in it as well as the relative amounts of each element in that substance.
* The symbols (s), (l), (g), and (aq) indicate the physical form or phase of a substance and whether it is dissolved in water.
*Lesson 7: Now You See It
* The Copper Cycle
*Check-in
* Imagine that you find a vial labeled Na2SO4(aq). What does the label tell you about what is in this vial?
* Compare and contrast “element” and “compound”
* What is the difference between (l) and (aq)?
*After this lesson You will be able
to:
* follow a lab procedure safely
* describe a chemical change or chemical
reaction
*Key Question
* What happens to matter when it is changed?
Read the lab procedure - pay close attention
to the safety precautions for today’s lab.
use
fume
hood
*Prepare for the Lab
During the lab, follow these safety guidelines:
* Wear your safety goggles at all times.
* Be very careful when handling chemicals. If any gets on your skin, wash the area immediately with water and inform your teacher.
* Use the fume hood when adding the nitric acid to the copper; do not breathe in any of the gas.
* When using the hot plate, set it at a medium setting. Be careful not to splash when stirring the chemicals.
* Remove the beaker from the hot plate with beaker tongs.
*Lab analysis
You could see copper only in the first and
last steps of the lab. Where do you think the
copper was the rest of the time? Be specific.
*Chemical changes
(reactions)
The copper cycle lab illustrates the process
of chemical reactions. You caused the
copper to undergo chemical changes.
Evidence of a chemical change is
the formation of “new”
substances.
An iron nail is left in contact with water and air and
forms a reddish brown coating (rust).
a. Is this a chemical change? What’s the evidence?
b. Is rust an element, a compound or a mixture?
Explain
c. How could you gather evidence to answer b above?
When a chemical change/reaction occurs, a
new substance is formed with different
chemical properties than the original
substance.
Clues of chemical changes:
• gas is formed
• precipitate is formed
• color change**
• light/sound
Chemical changes do not change the
underlying elements.
*A familiar example
NaHCO3(s) + CH3COOH(l) →
CO2(g) + H2O(l) + Na+(aq) + CH3COO-(aq)
*Lesson 8: What Goes Around
Comes Around
* Conservation of Matter
What do you think happened to the
copper powder in the copper cycle
experiment when it was mixed with the
nitric acid?
*Key Question
What happens to elements in a chemical change?
youtube
You could prove that copper was not
destroyed by measuring the mass of the
copper powder at the beginning and at
the end of the experiment.
•.
Law of conservation of mass: The law
states that mass cannot be gained or lost in
a chemical reaction–matter cannot be
created or destroyed, but it can change form.
Why might it be difficult to demonstrate the
Law of Conservation of Mass with your
copper cycle lab?
Chemical reaction:
Cool chemical reactions
reactants products
Chemical reactions occur when substances combine or
break apart. The starting substances are called reactants.
The ending substances are called the products.
In a chemical reaction, the end products have
different properties than each of the individual
reactants.
Chemical equations are a way to write out a
chemical reaction. They can be written in word form,
or in symbol form.
*an example:
Golden rain
potassium iodide + lead nitrate →
lead iodide + potassium nitrate
KI(aq) + Pb(NO3)2(aq) → PbI2 (s) + KNO3(aq)
*text notes
No matter what was done to the copper, it was
not broken down any further.
The observations we have made in the copper
cycle lab provide further evidence that the
golden penny is not gold.
*Lesson summary
What happens to elements in a chemical
change?
* Elemental copper can be transformed through
chemical reactions and then recovered.
* We can represent elements with symbols and keep
track of them during chemical reactions.
* Elements combine and recombine but are not
created or destroyed in chemical reactions.
Video summary
*Balancing chemical
equations
* remember: Compounds are represented
by chemical (molecular) formulas
2 Cl Cl2 2Cl2
• Molecules may also have brackets to
indicate numbers of atoms. E.g. Ca(OH)2
O H
O H
Ca
• Notice that the OH is a group
• The 2 refers to both H and O
a) NaOH
b) Ca(OH)2
c) 3Ca(OH)2
Na = 1, O = 1, H = 1
Ca = 1, O = 2, H = 2
Ca = 3, O = 6, H = 6
How many of each atom are in the
following?
*Law of conservation of
mass
Mass is not created or destroyed during a chemical reaction or physical change – but it can change form.
Must have same number of atoms before and
after the reaction.
When this condition is met, you have a
balanced equation.
Fe + O2 Fe2O3
Coefficients are written in front of the
formulas to satisfy the law of conservation
of mass.
2 3 4
*Balancing equations: MgO
Magnesium + Oxygen magnesium oxide
Mg + O2 MgO
O Mg O + Mg O
• However, this is not balanced
Left: Mg = 1, O = 2
Right: Mg = 1, O = 1
*Balance equations by
“inspection”
Mg + O2 MgO
2Mg + O2 2MgO is correct Mg + ½O2 MgO is incorrect
4Mg + 2O2 4MgO is incorrect
a) Mg + HCl MgCl2 + H2
b) Ca + N2 Ca3N2
c) NH4NO3 N2O + H2O
d) BiCl3 + H2S Bi2S3 + HCl
e) C4H10 + 13O2 8CO2 + 10H2O
f) 6 O2 + C6H12O6 CO2 + H2O
g) NO2 + H2O HNO3 + NO
h) Cr2(SO4)3+ NaOH Cr(OH)3+ Na2SO4
i) Al4C3 + H2O CH4 + Al(OH)3
Balance these skeleton equations: 2
3
3
3
2
2
2
2
3
3
2
6
6 6
6
12 4
*Lesson 9: Create A
Table
Properties of the Elements
*Check-in
Sodium chloride, NaCl (aq), is added to silver nitrate, AgNO3 (aq), resulting in NaNO3 (aq) and a white solid.
*Identify the white solid from the list below. Explain your choice.
A. AgCl (s) B. AgCl (aq)
*C. AgNO3(s) D. NaCl (s)
Chemical reaction of molten
NaCl
*Key Question
* Key Question:
How is the periodic table organized?
*You will be able to:
* describe how the organization of the periodic
table is based on reactivity and atomic mass
* predict the characteristics of a missing element
on the periodic table based on its position in the
table
* Work in groups of three with one set of Create a
Table cards for each group.
Aristotle
*Early Greeks
* 400 B.C. - Democritus thought matter could not
be divided indefinitely.
• 350 B.C - Aristotle modified an earlier theory that
matter was made of four “elements”: earth, fire,
water, air.
Democritus
Aristotle was wrong. However, his theory
persisted for 2000 years.
fire
air
water
earth
This led to the coining of the name “atom”.
*Dmitri Mendeleev
Early chemists understood
the importance of
relationships among chem.
and phys. properties of
elements.
*Mendeleyev organized his periodic table based on the
properties of the elements, such as reactivity and atomic
mass.
*Mendeleyev’s arrangement of the elements helped predict
the existence and properties of as-yet-undiscovered
elements.
What is reactivity?
Reactivity is a property that describes whether an
element or compound will chemically combine
with other substances to form compounds and
also describes the speed of a reaction.
Reactivity
of the Alkali
metals
Reactivity
information is
included on the
Create a Table
cards.
*A Closer Look at
Chemical
Reactions Reaction Lab
Bill Nye
*Reactivity is an important
chemical property of elements
Can we predict how different elements will
react?
Position in the
periodic table is
important.
Atomic Mass: The mass of a single
atom (or isotope) of an element.
Each element has an average atomic mass
that is expressed as a decimal number.
These are the
numbers that appear
on the Create a Table
cards.
*Examining patterns
Based on your table:
• What approach did you choose as your
main basis of organization?
• Did you have to abandon any
characteristics and pick different ones?
• Why didn’t everyone choose the same
method?
* examining patterns cont.
• What were some patterns you discovered in
your arrangement?
• Where did you put H and He? What was your
reasoning?
• Did you have any cards that didn’t fit your
pattern? Or were difficult to place?
Which card did you choose?
Where did you place it?
Reacts
slowly with
oxygen
Found in
GeH4 gas
Moderately
soft, silvery
solid,
metalloid
* examining
patterns cont
• Did you discover any new characteristics or
patterns in this activity?
• How do you think this organization of the
elements might be useful to chemists?
• How did Mendeleyev predict
new elements before they
were discovered?
*Patterns in the Periodic table
The Periodic Table contains tremendous
amounts of information about the elements.
Knowing the precise location of an element in
the Periodic table can help predict many of its
characteristics.
Mendeleyev organized his periodic table
based on the properties of the elements, such
as reactivity and atomic mass.
Mendeleyev’s arrangement of the elements
helped predict the existence and properties of
as-yet-undiscovered elements.
*summary
How is the periodic table organized? * Mendeleyev organized his periodic table based on
the properties of the elements, specifically, reactivity and atomic mass.
* Elements in each column of the periodic table have similar properties.
* Reactivity describes whether an element will chemically combine with other common substances and also describes the speed of the reaction.
* Mendeleyev’s arrangement of the elements helped predict the existence of undiscovered elements.
*Lesson 10: Breaking the
Code The Periodic Table
*Check-in
Which of these elements would be grouped
together on the periodic table? Explain your
thinking.
cadmium
Cd
moderately soft,
silvery, solid, metal
reacts very slowly
with water found in CdCl2(s)
zinc
Zn
moderately hard,
silvery, solid, metal
reacts very slowly
with water found in ZnCl2(s)
iodine
I
purple, solid,
nonmetal
reacts slowly with
metals found in ICl(s)
mercury
Hg silvery, liquid, metal
does not react
with water found in HgCl2(s)
Where would you place silver (Ag) and
gold (Au) in the periodic table you
created with your cards?
*Key Question
What information does the periodic table reveal about the
elements?
*You will be able to:
* use the periodic table to identify elements that are metals, nonmetals, metalloids, alkali metals, alkaline earth metals, transition elements, halogens, noble gasses, lanthanides, and actinides
* describe the general properties of elements, that are periodic in nature
* predict the general properties of an element based on its location on the periodic table and identify elements that will exhibit similar chemical behavior
In groups of four, sort the Create a Table cards
using the patterns you discovered in Lesson 9:
Create a Table.
Now open up the table to accommodate for more
elements.
*Evolution of the Periodic Table
Add Mendeleyev’s remaining elements.
Elements are arranged in the Periodic table based on their atomic number
the atomic number identifies the element
The atomic
number is equal
to the number of
protons in the
nucleus of the
element.
Important information about the
elements are shown:
Grouping elements shows a recurring,
periodic, predictable pattern.
Rows are called “periods”
Columns are called
“groups” or “families”
Elemental properties in periods increase/decrease as you move across the periodic table. The patterns in Periods repeat periodically over and over again.
*Periodic Table vocabulary
The Families of the periodic table
All elements in a family exhibit similar properties.
Lanthanides and actinides
If you examine the atomic numbers of these elements,
you’ll see they belong in the sixth and seventh
periods. They are “pulled out” and typically shown
below the Periodic Table merely for convenience.
Their periodic trends are consistent with the rest of the
table.
The elements of the periodic table can be broken into three
different groups: metals, metalloids (or semi-metals) and
nonmetals.
Alkali metals: The elements in Group 1A.
Alkaline earth metals: The elements in Group 2A.
Halogens: The elements in Group 7A.
Noble gases: The elements in Group 8A. They are called
“noble” gases because they are not reactive.
Periodic Families (Groups)
*The metals
Properties of Metals
• solid at room temperature (with
the exception of mercury)
• usually shiny
• high melting point
• good conductor of heat
• good conductor of electricity
• malleable – able to be pounded
into sheets
• ductile – can be pulled into wire
• high density (exceptions:
lithium, potassium and sodium)
• corrodes in air or seawater
• loses electrons in
reactions
alkali metal reactions.html
Specific metal families:
• they react with water to form hydroxide
ions, creating basic solutions (pH>7),
• among the most reactive metals
• Lowest electronegativity of all element
families.
• They produce bright, colorful flames
making them very useful in fireworks.
• shiny.
• silvery-white.
• somewhat reactive
metals at standard
temperature and
pressure.
• readily lose their two
outermost electrons to
form cations with a 2+
charge.
• low densities.
• low melting points.
• low boiling points.
Alkali earth
metals
Specific metal families:
*The nonmetals
Properties of nonmetals
• dull, not shiny
• poor conductor of heat
• poor conductor of electricity
• not malleable or ductile,
usually brittle
• lower density (when
compared to metals)
• lower melting point and
boiling points (when
compared to metals)
• gain electrons in
reactions
nonmetals
Many are gas at r.t. Solids tend to be brittle Low conductivity Poor conductors of heat
halogens
Noble gases
Gas at r.t. Non-reactive – have stable octets
metalloids
Characteristics of both metals and nonmetals
ALL are solid at r.t.
Semiconductors
Can gain and loose electrons in reactions
There is no standard definition of a metalloid, nor is there complete
agreement as to which elements are appropriately classified as such.
*More trends in the
Periodic Table
Elemental phases
Most elements are
solid at room
temperature
Hg
Ga
Br
Once the
elements are
arranged
according to
atomic number
and general
properties, many
other patterns
emerge.
There are
horizontal,
vertical and
diagonal!
patterns.
*Summary
*What information does the periodic table reveal about the elements?
* Patterns repeat on the periodic table. The table is organized so elements in each column of the periodic table have similar properties.
* The periodic table lists the name, symbol, and average atomic mass of each element.
* Several groups of elements and some periods have specific names, such as halogens or noble gasses.
* Metals are in the center and left, and nonmetals are at the top right; elements near the dividing line are considered metalloids.
*Compounds can be
separated based on their
size and charge.