# Objective 4 ```Objective 4
► The
student will demonstrate an
understanding of the structures and
properties of matter.
3 overarching TEKS
► IPC(7)
The student knows relationships
exist between properties of matter and its
components.
► IPC(8) The student knows that changes in
matter affect everyday life.
► IPC(9) The student knows how solution
chemistry is a part of everyday life.
7(A)
►
Density: The amount of matter per given space (volume). The
formula to calculate density is D = mass/volume and is
found on the formula chart. The density of an object does not
change by changing the volume. Solids are more dense than
liquids and liquids are more dense than gases.
►
Viscosity: The resistance of fluids to flow. Thick fluids flow
slower than thin ones do. Oil flows more slowly than water,
thus, oil is more viscous than water.
►
Buoyancy: The force with which a more dense fluid pushes a
less dense substance upward. The student will have to
compare the densities of two substances and will need to
know that the more dense substance will be below the less
dense. You will have to know that the density of water is 1
g/cm3 .
► 1) A sample of an element has a volume of 78.0 mL
and a density of 1.85 g/mL. What is the mass in
nearest tenth.
► a.What does 78.0 represent?
 Mass
► b.
density
temperature
What does 1.85 represent?
 Mass
► c.
volume
volume
density
temperature
What is the question asking you to calculate?
 Mass
volume
density
temperature
Cont. problem
►
►
1) A sample of an element has a volume of 78.0
mL and a
78.0 mL
density of 1.85
1.85 g/mL.
g/mL What is the mass
mass in grams of the
d. What formula will you use from the formula sheet?
D
►
=
Mass
volume
e. Substitute numbers from the problem into the formula?
=
►
f. Calculate the unknown to the nearest tenth.
144.3 g
Another question
6) The picture shows the results of pouring a
blue liquid into a clear liquid and allowing the
mixture to settle for 25 minutes. Compared
to the clear liquid, the blue liquid is more —
► A massive
► B dense
► C viscous
► D soluble
See buoyancy notes.
7(D)
►
►
►
►
►
►
►
The periodic table organizes the elements into a grid of horizontal
rows (left to right) called periods and vertical columns (up and
down) called groups or families.
– there are 18 groups
- groups 1,2,13,14,15,16,17,18 have the pattern of representing the
number of valence (outermost) electrons an atom of that
element has; 1,2,3,4,5,6,7,8 electrons, respectively.
- groups 1 &amp; 2 want to lose their total valance electrons.
- groups 13-17 nonmetals want to gain or accept extra
electrons to have a total of 8 valence electrons.
- group 18 does not loose or gain electrons, thus becoming
non reactive.
-elements in the same group have similar chemical and physical
properties because they have the same number of valance
electrons.
7(D)
► The
zigzag line on the periodic table separates
metals from nonmetals – elements to the right of
the line are nonmetals and elements to the left of
the line are metals.
► The metals want to react with the nonmetals,
except group 18.
►
-The formulas for these compounds are written
by balancing charges. The total positive charge
has to cancel the total negative charge. This can
be accomplished by the drop and swap method –
drop the charge and swap the number of the
charge as a subscript of the other element or ion.
Ex Problems
1 Which of the following groups contains members with
similar chemical reactivity?
A Li, Be, C
All in group 2
B Be, Mg, Sr
C Sc, Y, Zr
D C, N, O
2 According to this information, what is the chemical formula
for aluminum sulfate?
A AlSO4
B Al2(SO4)3
C Al3(SO4 )2
Drop and Swap
D Al6 SO4
7(E)
► Element:
is a pure substance that can not be
broken down into simpler substances.
► Symbol form - “C” for carbon, “Ni” for nickel
*notice one capital letter.
► Word form – nitrogen, magnesium *words
found on the periodic table
► You will need to be able to identify an atom from
its model. Atomic number represents number of
protons (+ charge)
7(E)
► Compound:
a combination of 2 or more elements
that are combined chemically. There are two
common compounds to memorize; water (H2O)
and table salt (NaCl).
► Symbol form – CaBr2 ; Mg(NO3)2
*notice two or
more capital letters.
► Word form – calcium bromide; magnesium nitrate
*notice two elements names from the periodic
table.
7(E)
► Mixture:
two or more compounds and/or
elements together that are not chemically
combined.
periodic table.
Ex Questions
1 An unknown silvery powder has a constant melting
point and does not chemically or physically separate into
other substances. The unknown substance can be
classified as —
A an element
B a compound
C a mixture
D an alloy
► 2 The picture shows a model of the element —
A fluorine
4 protons so
B helium
look at atom
C beryllium
number 4
D oxygen
►
8(A)
Chemical Change: A process that involves one or
more substances changing into new substances.
►
Key words: explode, rust, oxidize, corrode,
tarnish, ferment, burn, rot, reacts
► Physical Change: A process that alters a substance
without changing its composition.
►
Key words: bend, grind, crumple, split, crush,
melt, condense, evaporate, boil, freeze.
► The questions on TAKS will be about the rock cycle,
digestive system, changes in state (water freezing,
evaporating, condensing), and oxidation (rusting,
burning, decomposing). You will have to decide if
the change is chemical or physical.
►
Ex. Questions
1) Which of the following is an example of a chemical change?
A Combustion of gasoline
B An apple being bitten
C An ice cube being swallowed
D Absorption of a water molecule
►
2 Which of the following processes is an example of a physical
change associated with an oak tree?
A Decomposition of bark by bracket fungi
B Starches and sugars being broken down during energy
production
C Water and carbon dioxide being converted to glucose
D Evaporation of water from the surfaces of leaves
►
8(C) Law of conservation of mass
There are two basic questions on TAKS on this TEK:
1) choosing a balanced equation or balance one.
2) making sure the mass of reactants equal the mass of
products.
► BALANCING EQUATIONS:
► Let’s first review counting atoms in a chemical formula.
► The numbers to the lower right of each chemical symbol,
called the subscript, tells how many of those atoms make
up the compound.
► If no number appears, then there is considered only one of
those atoms.
►
H2 O
8(C)

The numbers in front of the chemical formula are
called coefficients and tell how many compounds
are represented.
O
2H2O
O
H
2 water molecules
H
H
H
So 4 hydrogens and 2 oxygens. You multiply the
coefficients by the subscripts for counting.
Ex. Problem
What are the coefficients that will balance this chemical
equation?
A 2, 1, 1
B 3, 4, 2
C 2, 2, 1
D 4, 3, 2
Cont. 8(C) Law of conservation of
mass
► MASSES
OF REACTANTS EQUAL TO
MASSES OF PRODUCTS
► Remember that reactants are on the left
side of the arrow and products are on the
right side of the arrow.
Ex. Problem
According to the law of conservation of mass, how much
zinc was present in the zinc carbonate?
A 40 g
B 88 g
64g + 192g = 152g + ?
C 104 g
D 256 g
9(A) Relate the structure of water to
its function [as a universal solvent].
► The
water molecule (H2O) is a polar molecule –
meaning that one end of the molecule is slightly
(δ+) positive and the other end is slightly (δ-)
negative.
►
-the difference in charges allows the water
molecule to surround charged particles and thus
dissolve them.
► The water molecule is also important because its
solid form (ice) is less dense than its liquid form.
Thus, ice floats on water to form a protective
insulation to prevent further freezing.
Water molecules surrounding ions.
Positive end of
water (H)
Negative end
of water (O)
Ex. Problem
Fish survive through severe winters because of the property of water that
allows water to —
F form chemical bonds as it freezes, raising the water temperature
below the ice
G increase in density while it freezes, dissolving more oxygen from the
air
H expand when it freezes, creating a floating and insulating layer of ice
J precipitate vital nutrients when it freezes, increasing the food supply
Water acts as a solvent of ionic compounds because —
F water is liquid over a wide range of temperatures
G water molecules are polar
H water is found in three states of matter
J water takes the shape of its container
9(B)relate the concentration of ions in a solution to
physical and chemical properties such as pH,
electrolytic behavior, and reactivity.
► Concentration
of ions is the amount of ions per
given volume. Concentration can be expressed as
percent(%) solution.
► pH is the measure of H+ ions in water. The “p” in
pH means power, so, pH means power of H+ ions
in solution. We have the pH scale that is used to
measure the acidity of solutions. The higher
concentration of [H+] the greater the acidity, but
can be confusing when looking at the pH scale
because lower pH means more acidity.
► One cause of Acid rain is by burning fossil fuels.
This is pH.
Notice as pH
decreases,
[H+] increases
and becomes
more acidic.
Electrolytic behavior
►
Electrolytic behavior of a solution is its ability to conduct
electricity. The more ions are dissolved in water the
greater the conduction of electricity. In the picture below,
seawater has lots of salt dissolved in water making
electricity flow through it.
The greater the
concentration of ions
the brighter the light.
Ex. Problem
The table shows data from an investigation designed to find a
liquid solution that is both an acid and a strong electrolyte. Based
on the data, a solution that is both an acid and a strong
electrolyte is —
A Solution 1
B Solution 2
C Solution 3
D Solution 4
Bathwater normally has electrolytic behaviors
even though distilled water does not. This is
because bathwater —
► F contains isotopes of hydrogen
► G has been heated
► H is separated into H+ and OH– ions
► J contains dissolved minerals
9(D) demonstrate how various factors influence solubility
including temperature, pressure, and nature of the solute and
solvent.
►
►
►
In most cases the solvent will be water and the solute will
be what ever is being dissolved. Some things do not
dissolve and are thus called insoluble. Some substances,
compounds or elements, are more soluble than others.
There are Solubility Rules that scientist follow but is not
required to memorize for TAKS.
Several factors affect solubility for solids and gases.
These are the factors for solids:




increasing temperature of solvent (water) increases solubility.
crushing or increasing surface area increases solubility.
stirring or agitation increases solubility.
pressure does not affect solubility of solids.
9(D) cont.
Notice the trend
between solubility
and temperature.
9(D) continue
► Gases:
 increasing temperature of solvent decreases
solubility of gases. (heating a can of soda
makes it fizz)
 stirring or agitation of solvent decreases
solubility of gases. (shaking a soda)
 increasing pressure of gas above solvent
increases solubility – pushes gas into water.
► *Notice the relationship between temperature and
solubility of gases in the table.
Ex. Problems
Pain medications can be made as powders or tablets. The powders tend to
work faster than tablets with the same ingredients because powder —
F dissolves faster in solution than a single tablet
G has more total mass than a single tablet
H travels through the bloodstream more easily than a tablet
J is easier to swallow than tablets
Over time an open soft drink will lose carbonation (dissolved CO2). Which of
these allows the CO2 to remain in solution the longest?
A Reduced air pressure
B Exposure to direct sunlight
C Increased air currents
D Cooler temperatures
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