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Chapter 4
Matter and
Energy
Vanessa N. Prasad-Permaul
CHM 1025
Valencia Community College
1
Matter

Matter is any substance that has mass and
occupies volume.

Matter exists in one of three physical states:
1.
Solid
2.
Liquid
3.
Gas
2
Gaseous State
 In a gas, the particles of matter are far apart
and uniformly distributed throughout the
container.
 Gases have an indefinite shape and assume
the shape of their container.
 Gases can be compressed and have an
indefinite volume.
 Gases have the most energy of the three
states of matter.
3
Liquid State
 In a liquid, the particles of matter are loosely
packed and are free to move past one
another.
 Liquids have an indefinite shape and assume
the shape of their container.
 Liquids cannot be compressed and have a
definite volume.
 Liquids have less energy than gases, but more
energy than solids.
4
Solid State
 In a solid, the particles of matter are tightly
packed together.
 Solids have a definite, fixed shape.
 Solids cannot be compressed and have a
definite volume.
 Solids have the least energy of the three
states of matter.
5
Physical States of Matter
6
Changes in Physical States
 Most substances can exist as either a solid, a
liquid, or a gas.
 Water exists as a solid below 0 °C; as a liquid
between 0 °C and 100 °C; and as a gas above
100 °C.
 A substance can change physical states as the
temperature changes.
7
Solid ↔ Liquid Phase Changes
 When a solid changes to a liquid, the phase
change is called melting.
 A substance melts as the temperature
increases.
 When a liquid changes to a solid, the phase
change is called freezing.
 A substance freezes as the temperature
decreases.
8
Liquid ↔ Gas Phase Changes
 When a liquid changes to a gas, the phase
change is called vaporization.
 A substance vaporizes as the temperature
increases.
 When a gas changes to a liquid, the phase
change is called condensation.
 A substance condenses as the temperature
decreases.
9
Solid ↔ Gas Phase Changes
 When a solid changes directly to a gas, the
phase change is called sublimation.
 A substance sublimes as the temperature
increases.
 When a gas changes directly to a
solid, the phase change is
called deposition.
 A substance undergoes
deposition as the
temperature decreases.
10
Summary of State Changes
11
EXAMPLE 4.1 Change of Physical State
State the term that applies to each of the following changes of
physical state:
(a) Snow changes from a solid to a liquid.
(b) Gasoline changes from a liquid to a gas.
(c) Dry ice changes from a solid to a gas.
Solution
Refer to Figure 4.1 for the changes of
physical state.
(a) The change from solid to liquid is
called melting.
(b) The change from liquid to gas is
called vaporizing.
(c) The change from solid to gas is
called sublimation.
Figure 4.1 Changes in Physical State As temperature increases, a solid melts to a liquid and then vaporizes into a
gas. As temperature decreases, a gas condenses to a liquid and then freezes to a solid.
EXERCISE 4.1 Change of Physical State
Practice Exercise
State the term that applies to
each of the following changes of
physical state:
(a) A refrigerant changes from a
gas to a liquid.
(b) Water changes from a liquid
to a solid.
(c) Iodine vapor changes from a
gas to a solid.
Figure 4.1 Changes in Physical State As temperature increases, a solid melts to a liquid and then vaporizes into
a gas. As temperature decreases, a gas condenses to a liquid and then freezes to a solid.
EXERCISE 4.1 Change of Physical State
Concept Exercise
Identify the physical state (solid, liquid, gas) that corresponds
to each of the following pictorial representations:
Classifications of Matter

Matter can be divided into two classes:
1.
Mixtures
2.
Pure substances

Mixtures are composed of more than one
substance and can be physically separated
into its component substances.

Pure substances are composed of only one
substance and cannot be physically
separated.
15
Mixtures
 There are two types of mixtures:
1. Homogeneous mixtures
2. Heterogeneous mixtures
 Homogeneous mixtures have uniform
properties throughout.
 Salt water is a homogeneous mixture.
 Heterogeneous mixtures do not have
uniform properties throughout.
 Sand and water is a heterogeneous mixture.
16
Pure Substances

There are two types of pure substances:
1.
Compounds
2.
Elements

Compounds can be chemically separated
into individual elements.


Water is a compound that can be separated into
hydrogen and oxygen.
An element cannot be broken down further
by chemical reactions.
17
Matter Summary
18
EXAMPLE 4.2 Element, Compound, or Mixture
Consider the following properties of the element copper:
(a)
(b)
(c)
(d)
Copper metal cannot be broken down by a
chemical change.
Copper reacts with oxygen in air to give copper
oxide.
Copper, in the form of malachite ore, is found
worldwide.
Copper and tin compose bronze alloy.
Classify each of the following copper samples as an
element,
a compound, a homogeneous mixture, or a heterogeneous
mixture:
(a) copper wire
(b) copper oxide
(c) malachite ore
(d) bronze alloy
Solution
Refer to Figure 4.2 to classify each sample.
(a) Copper wire is a metallic element.
(b) Copper oxide is a compound of the elements
copper and oxygen.
(c) Malachite ore is a heterogeneous mixture of
copper and other substances.
(d) Bronze alloy is a homogeneous mixture of
copper and tin.
Figure 4.2 Classification of Matter Matter may be either
a mixture or a pure substance. The properties of a
heterogeneous mixture vary within the sample (oil and
water). The properties of a homogeneous mixture are
constant (salt solution). A pure substance may be either a
compound (water) or an element (gold). Left to right: oil
and water; NaCl solution; H2O; and gold nugget.
EXERCISE 4.2 Element, Compound, or Mixture
Practice Exercise
Consider the following properties of the element mercury:
(a) Mercury liquid cannot be broken down by a chemical change.
(b) Mercury oxide can be heated to give mercury and oxygen gas.
(c) Mercury, in the form of cinnabar ore, is found in Spain and Italy.
(d) Mercury and silver compose the alloy used for dental fillings.
Classify each of the following mercury samples as an element, a
compound, a homogeneous mixture, or a heterogeneous mixture:
(a) mercury liquid (b) mercury oxide
(c) cinnabar ore (d) dental alloy
EXERCISE 4.2 Element, Compound, or Mixture
Concept Exercise
Classify each of the following as an element, a compound, or a
mixture as shown in the illustration:
Occurrence of the Elements
 There are over 100 elements that occur in nature; 81
of those elements are stable.
 Only 10 elements account for 95% of the mass of
Earth’s crust:
22
Elements in the Human Body
 Oxygen is the most common element in
Earth’s crust and in the human body.
 While silicon is the second most abundant
element in Earth’s crust, carbon is the second
most abundant in the body.
23
Names of the Elements
 Each element has a unique name.
 Names have several origins:
 Hydrogen is derived from Greek.
 Carbon is derived from Latin.
 Scandium is named for Scandinavia.
 Nobelium is named for Alfred Nobel.
 Yttrium is named for the town of Ytterby, Sweden.
24
Element Symbols
 Each element is abbreviated using a chemical
symbol.
 The symbols are one or two letters long.
 Most of the time, the symbol is derived from
the name of the element.
 C is the symbol for carbon.
 Cd is the symbol for cadmium.
 When a symbol has two letters, the first is
capitalized and the second is lowercase.
25
Other Element Symbols
 For some elements, the chemical symbol is derived
from the original Latin name.
Gold – Au
Sodium – Na
Silver – Ag
Antimony – Sb
Copper – Cu
Tin – Sn
Mercury – Hg
Iron – Fe
Potassium – K
Tungsten – W
26
Types of Elements


Elements can be divided into three classes:
1.
Metals
2.
Nonmetals
3.
Semimetals or metalloids
Semimetals have properties midway
between those of metals and nonmetals.
27
Metal Properties
 Metals are typically solids with high melting
points and high densities and have a bright,
metallic luster.
 Metals are good conductors of heat and
electricity.
 Metals can be hammered into thin sheets and
are said to be malleable.
 Metals can be drawn into fine wires and are
said to be ductile.
28
Nonmetal Properties
 Nonmetals typically have low melting points
and low densities and have a dull appearance.
 Nonmetals are poor conductors of heat and
electricity.
 Nonmetals are not malleable or ductile and
crush into a powder when hammered.
 Eleven nonmetals occur naturally in the
gaseous state.
29
Summary of Properties
30
Periodic Table of the
Elements
 Each element is assigned a number to
identify it. It is called the atomic number.
 Hydrogen’s atomic number is 1; helium is 2;
up to uranium, which is 92.
 The elements are arranged by atomic number
on the periodic table.
31
The Periodic Table
32
Metals, Nonmetals, & Semimetals
 Metals are on the left side of the periodic table,
nonmetals are on the right side, and the semimetals
are in between.
33
Physical States of the Elements
Shown are the physical states of the elements at 25 °C
on the periodic table.
34
Law of Definite Composition
 The law of definite composition states that
“Compounds always contain the same
elements in a constant proportion by mass.”
 Water is always 11.19% hydrogen and 88.81%
oxygen by mass, no matter what its source.
 Ethanol is always 13.13% hydrogen, 52.14%
carbon, and 34.73% oxygen by mass.
35
Chemical Formulas
 A particle composed of two or more
nonmetal atoms is a molecule.
 A chemical formula is an expression of the
number of and types of atoms in a molecule.
 The chemical formula of
sulfuric acid is H2SO4.
36
Writing Chemical Formulas
 The number of each type of atom in a molecule
is indicated with a subscript in a chemical
formula.
 If there is only one atom of a certain type, no “1”
is used.
 A molecule of the vitamin niacin has six carbon
atoms, six hydrogen atoms, two nitrogen atoms,
and one oxygen atom. What is the chemical
formula?
C6H6N2O
37
Interpreting Chemical
Formulas
 Some chemical formulas use parentheses to
clarify atomic composition.
 Ethylene glycol, a component of some
antifreezes, has a chemical formula of
C2H4(OH)2. It contains two carbon atoms, four
hydrogen atoms, and two OH units, giving a
total of six hydrogen atoms and two oxygen
atoms. How many total atoms are in
ethylene glycol?
 Ethylene glycol has a total of ten atoms.
38
Physical and Chemical
Properties
 A physical property is a characteristic of a
pure substance that we can observe without
changing its composition.
 Physical properties include appearance,
melting and boiling points, density,
conductivity, and physical state.
 A chemical property describes the chemical
reactions of a pure substance.
39
Chemical Properties
Sodium metal (Na)
reacts with
chlorine gas (Cl2)
to produce
sodium chloride (NaCl).
40
Physical and Chemical Change
 A physical change is a change where the
chemical composition of the substance is not
changed.
 These include changes in physical state or
shape of a pure substance.
 A chemical change is a chemical reaction.
 The composition of the substances changes
during a chemical change.
41
Evidence for Chemical Changes
 Gas release (bubbles)
 Light or release of heat energy
 Formation of a precipitate
 A permanent color change
42
Conservation of Mass
 Antoine Lavoisier found that the mass of
substances before a chemical change was
always equal to the mass of substances after
a chemical change.
 This is the law of conservation of mass.
 Matter is neither created nor destroyed in
physical or chemical processes.
43
Conservation of Mass Example
 If 1.0 gram of hydrogen combines with 8.0
grams of oxygen, 9.0 grams of water is
produced.
 Consequently, 3.0 grams of hydrogen
combine with 24.0 grams of oxygen to
produce 27.0 grams of water.
 If 50.0 grams of water decompose to produce
45.0 grams of oxygen, how many grams of
hydrogen are produced?
50.0 g water – 45.0 g oxygen = 5.0 g hydrogen
44
Potential and Kinetic Energy
 Potential energy, PE, is stored energy; it
results from position or composition.
 Kinetic energy, KE, is the energy matter has
as a result of motion.
 Energy can be converted between the two
types.
 A boulder at the top of the hill has potential
energy; if you push it down the hill, the
potential energy is converted to kinetic energy.
45
Energy
46
KE, Temperature, and Physical
State
 All substances have kinetic energy regardless of
their physical state.
 Solids have the lowest kinetic energy, and gases
have the greatest kinetic energy.
 As you increase the temperature of a substance, its
kinetic energy increases.
47
Law of Conservation of
Energy

Just like matter, energy cannot be created or destroyed,
but it can be converted from one form to another.

This is the law of conservation of energy.

There are six forms of energy:
1.
Heat
2.
Light
3.
Electrical
4.
Mechanical
5.
Chemical
6.
Nuclear
48
Energy and Chemical Changes
 In a chemical change, energy is transformed
from one form to another. For example:
49
Law of Conservation of Mass and
Energy
 Mass and energy are related by Einstein’s theory
of relativity, E = mc2.
 Mass and energy can be interchanged.
 The law of conservation of
and energy states that
mass and energy of
mass
the total
the universe is
constant.
50
Chemistry Connection: Al
Recycling
 Although aluminum is very
abundant in Earth’s crust, it
is difficult to purify it from
its ore.
 The energy from 8 tons of
coal is required to produce 1
ton of aluminum metal
from its ore.
 However, it only takes the
energy from 0.4 tons of coal
to produce 1 ton of
aluminum from recycled
scrap.
51
Chapter Summary

Matter exists in three physical states:
1.
Solid
2.
Liquid
3.
Gas

Substances can be converted between the
three states.

Substances can be mixtures or pure
substances.
52
Chapter Summary, Continued
 Pure substances can be either compound or
elements.
 The elements are arranged in the periodic
table.
 Each element has a name and a one- or two-
letter symbol.
 Elements are classified as either metals,
nonmetals, or semimetals.
53
Chapter Summary, Continued
 A physical change is a change in physical
state or shape.
 A chemical change is a change in the
chemical composition of a substance.
 Both mass and energy are conserved in
chemical and physical changes.
54
EXAMPLE EXERCISE 4.3 Properties of Metals
Which of the following properties is not characteristic of a metal?
(a) good conductor of heat
(b) malleable
(c) high melting point
(d) reacts with other metals
Solution
Refer to Table 4.4 to classify each of the following properties:
(a) Metals are good conductors of heat.
(b) Metals are malleable.
(c) Metals usually have high melting points.
(d) Metals do not react with other metals; they mix to form alloys.
EXAMPLE EXERCISE 4.3 Properties of Metals
Continued
Practice Exercise
Which of the following properties is not characteristic of a
nonmetal?
(a) insulator of electricity (b)
ductile
(c) low density
(d)
reacts with nonmetals
Answer: (b) Nonmetals crush to a powder and are not
malleable or ductile.
Concept Exercise
Which of the following is a solid metal under normal
conditions: calcium, phosphorus, mercury, or silicon?
(Refer to Figure 4.7.)
Answer: See Appendix G.
Figure 4.7 Pictorial Periodic Table of the Elements The natural abundance is the percent by mass of an
element in Earth’s crust, oceans, and atmosphere. The natural abundance of an element listed as rare is less than
1 mg per metric ton (1000 kg). An element listed as synthetic is made artificially and does not occur naturally.
An element listed as unstable often disintegrates in a fraction of a second.
EXAMPLE EXERCISE 4.4 Physical States of the Elements
Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each element
as a metal, nonmetal, or semimetal:
(a) barium
(b) boron
(c) bismuth
(d) bromine
Solution
Referring to Figures 4.5 and 4.6, we observe the following:
(a) Barium (Ba) is on the left side of the periodic table; it is a solid metal under normal conditions.
(b) Boron (B) is in the middle of the periodic table; it is a solid semimetal.
(c) Bismuth (Bi) is to the right, but below the semimetals in the periodic table, it is a solid metal.
(d) Bromine (Br) is on the right side of the periodic table; it is a liquid nonmetal at normal conditions.
Figure 4.5 Metals, Nonmetals, and
Semimetals The symbols of elements
having metallic properties are on the
left side of the periodic table,
nonmetallic are on the right side, and
semimetallic are midway between.
Notice the special placement of
hydrogen, a nonmetallic element.
EXAMPLE EXERCISE 4.4 Physical States of the Elements
Continued
Figure 4.6 Physical States of the
Elements At 25 °C and normal
atmospheric pressure, all metals are in the
solid state except Hg. Most nonmetals are
gases except C, P, S, Se, and I, which
are solids. The only elements in the liquid
state at normal conditions are Hg and Br.
Practice Exercise
Indicate the physical state for each of the following elements at 25 °C and normal pressure; classify each
element as a metal, nonmetal, or semimetal:
(a) aluminum
(b) hydrogen
(c) helium
(d) radium
Answers: (a) solid metal; (b) gaseous nonmetal; (c) gaseous nonmetal; (d) solid metal
EXAMPLE EXERCISE 4.4 Physical States of the Elements
Continued
Concept Exercise
Which of the following is a liquid nonmetal under
normal conditions: sodium, mercury, bromine, or
sulfur? (Refer back to Figure 4.7.)
Answer: See Appendix G.
Figure 4.7 Pictorial Periodic Table of the
Elements The natural abundance is the percent by
mass of an element in Earth’s crust, oceans, and
atmosphere. The natural abundance of an element
listed as rare is less than 1 mg per metric ton
(1000 kg). An element listed as synthetic is made
artificially and does not occur naturally. An element
listed as unstable often disintegrates in a fraction of
a second.
EXAMPLE EXERCISE 4.5 Composition of Chemical Formulas
State the total number of atoms in a molecule of vitamin B 3, C6H6N2O.
Solution
The chemical formula for vitamin B3 indicates 6 carbon atoms, 6 hydrogen atoms, 2 nitrogen atoms, and
1 oxygen atom. Thus C6H6N2O has a total of 15 atoms.
Practice Exercise
Write the chemical formula for vitamin B6, if a molecule is composed of 8 carbon atoms, 11 hydrogen
atoms, 1 nitrogen atom, and 3 oxygen atoms.
Answer: C8H11NO3 (total of 23 atoms)
Concept Exercise
Examine the model for vitamin C and
determine the molecular formula. In the
model shown, the black sphere = C atom,
white = H atom, and red = O atom.
Answer: See Appendix G.
EXAMPLE EXERCISE 4.6 Composition of Chemical Formulas
State the total number of atoms in a molecule of glycerin, C 3H5(OH)3.
Solution
The chemical formula for glycerin indicates 3 carbon atoms, 5 hydrogen atoms, and 3 OH units. Thus,
C3H5(OH)3 has a total of 14 atoms.
Practice Exercise
Write the chemical formula for nitroglycerin if a molecule is composed of 3 carbon atoms,
5 hydrogen atoms, 3 oxygen atoms, and 3 NO2 units.
Answer: C3H5O3(NO2)3
Concept Exercise
State the total number of atoms in a molecule of nitroglycerin, C 3H5O3(NO2)3.
Answer: See Appendix G.
EXAMPLE EXERCISE 4.7 Physical and Chemical Properties
Classify each of the following properties as physical or chemical:
(a) Water appears colorless and odorless at 20 °C.
(b) Water dissolves sugar crystals.
(c) Water produces a gas with calcium metal.
(d) Water exists as ice at –10 °C.
Solution
If a reaction occurs, there is a change in composition and the property is chemical. Otherwise, the property
is physical.
(a) Color and odor are physical properties.
(b) Solubility is a physical property.
(c) A chemical reaction is a chemical property.
(d) A physical state is a physical property.
Practice Exercise
Classify each of the following properties as physical or chemical:
(a) Water appears hard and crystalline at 0 °C.
(b) Water is insoluble in gasoline.
(c) Water is a very weak conductor of electricity.
(d) Water produces a gas with sodium metal.
Answers: (a) physical; (b) physical; (c) physical; (d) chemical
Concept Exercise
Copper melts at 1083 °C, has a density of 8.92 g/mL, is a good conductor of electricity, and turns black
when heated. Which of these is an example of a chemical property?
Answer: See Appendix G.
EXAMPLE EXERCISE 4.8 Physical and Chemical Changes
Classify each of the following observations as a physical or a chemical change:
(a) Touching a lit candle to hydrogen soap bubbles gives an explosion.
(b) Heating water in a flask produces moisture on the glass.
(c) Combining two colorless solutions gives a yellow solid.
(d) Pouring vinegar on baking soda produces gas bubbles.
Solution
An observation that indicates a physical change is a change of physical state. The observations that suggest
a chemical change include burning, fizzing, changing color, or forming an insoluble substance in solution.
(a) Hydrogen explodes; thus, it is a chemical change.
(b) Water is boiled; thus, it is a physical change.
(c) Two solutions give an insoluble substance; thus, it is a chemical change.
(d) Baking soda fizzes; thus, it is a chemical change.
Practice Exercise
Classify each of the following observations as a physical or a chemical change:
(a) Freezing water in a refrigerator makes cubes of ice.
(b) Adding silver nitrate to tap water gives a cloudy solution.
(c) Burning sulfur gives a light blue flame.
(d) Grinding aspirin tablets produces a powder.
Answers: (a) physical; (b) chemical; (c) chemical; (d) physical
EXAMPLE EXERCISE 4.8 Physical and Chemical Changes
Continued
Concept Exercise
An Alka-Seltzer tablet dissolves in water and produces gas
bubbles. Is this an example of a physical change or a chemical
change?
Answer: See Appendix G.
Alka-Seltzer An Alka-Seltzer tablet in water
releases carbon dioxide gas bubbles.
EXAMPLE EXERCISE 4.9 Conservation of Mass Law
In an experiment, 2.430 g of magnesium metal was ignited and burned with oxygen in the air. If 4.030 g of white
magnesium oxide powder, MgO, was collected, what was the mass of oxygen gas that reacted?
Solution
Applying the conservation of mass law, we find that the mass of the magnesium metal plus the mass of the
oxygen gas equals the mass of the magnesium oxide powder. That is,
2.430 g Mg + mass of oxygen = 4.030 g MgO
mass of oxygen = 4.030 g MgO – 2.430 g Mg
mass of oxygen = 1.600 g
Practice Exercise
If 0.654 g of zinc metal reacts with 0.321 g of yellow powdered sulfur, what is the mass of the zinc sulfide
produced?
Answer: 0.975 g
Concept Exercise
Heating 1.000 g copper metal with yellow sulfur produces 1.252 g of black copper sulfide. What is the mass
of sulfur that reacted with the copper metal?
Answer: See Appendix G.
EXAMPLE EXERCISE 4.10 Kinetic Energy and Molecular Motion
A balloon filled with helium gas is cooled from 25 °C to –25 °C. State the change in each of the following:
(a) kinetic energy of the gas
(b) motion of helium atoms
Solution
Temperature, kinetic energy, and velocity are related as follows:
(a) As the temperature cools from 25 °C to –25 °C, the kinetic energy of helium
atoms decreases.
(b) Since a drop in temperature produces a decrease in kinetic energy, the motion of helium atoms
decreases.
Practice Exercise
A steel cylinder containing air is heated from 25 °C to 50 °C. State the change in each of
the following:
(a) kinetic energy of the gas
(b) motion of air molecules
Answers: (a) increases; (b) increases
Concept Exercise
What happens to the kinetic energy and velocity of air molecules when the temperature increases?
Answer: See Appendix G.
EXAMPLE EXERCISE 4.11 Forms of Energy
Identify two forms of energy that are involved in each of the following conversions:
(a) Radioactive emissions vaporize water to steam.
(b) Steam drives a turbine.
(c) A turbine spins and drives an electrical generator.
Solution
We can refer to the six forms of energy listed above. It follows that
(a) Nuclear energy is converted to heat energy.
(b) Heat energy is converted to mechanical energy.
(c) Mechanical energy is converted to electrical energy.
Practice Exercise
Identify two forms of energy that are involved in each of the following devices:
(a) flashlight
(b) solar calculator
(c) lead–acid battery
Answers: (a) chemical and light; (b) light and electrical; (c) chemical and electrical
Concept Exercise
Which of the following is not a basic form of energy: chemical, electrical, heat, light, mechanical, nuclear,
solar?
Answer: See Appendix G.
The change from gas to solid is
called
a. condensing.
b. deposition.
c. freezing.
d. sublimation.
© 2011 Pearson Education, Inc.
The change from gas to solid is
called
a. condensing.
b. deposition.
c. freezing.
d. sublimation.
© 2011 Pearson Education, Inc.
Air is an example of a(n)
a. compound.
b. element.
c. heterogeneous mixture.
d. homogeneous mixture.
© 2011 Pearson Education, Inc.
Air is an example of a(n)
a. compound.
b. element.
c. heterogeneous mixture.
d. homogeneous mixture.
© 2011 Pearson Education, Inc.
Ca is the symbol of the element
a. cadmium.
b. calcium.
c. californium.
d. carbon.
© 2011 Pearson Education, Inc.
Ca is the symbol of the element
a. cadmium.
b. calcium.
c. californium.
d. carbon.
© 2011 Pearson Education, Inc.
Which is classified as a
nonmetal?
a. P
b. As
c. Sb
d. All of the above
© 2011 Pearson Education, Inc.
Which is classified as a
nonmetal?
a. P
b. As
c. Sb
d. All of the above
© 2011 Pearson Education, Inc.
How many atoms are in a
molecule of trinitrotoluene,
C7H5(NO2)3?
a. 3
b. 4
c. 15
d. 21
© 2011 Pearson Education, Inc.
How many atoms are in a
molecule of trinitrotoluene,
C7H5(NO2)3?
a. 3
b. 4
c. 15
d. 21
© 2011 Pearson Education, Inc.
Example 1: Molecular Formula
Glucose contains 6 carbons, 12 hydrogens, and 6
oxygens. Write the molecular formula for glucose
78
Example 2: Molecular Formula
List how many of each type of element the following
compounds have
A) H2O
B) NH3
C) C2H4(OH)2
79
Example 3: Conservation of Mass
C(s) + O2(g)  CO2(g)
a)
12.3g C reacts with 32.8g O2, ?g CO2
b) 0.238g C reacts with ?g O2 to make .873g CO2
c)
?g C reacts with 1.63g O2 to make 2.24g CO2
80