CHAPTER 1
MOLECULAR REASONS
ANSWERS TO QUESTIONS:
1. All natural phenomena in the world we can see are the result of invisible molecular
interactions.
Examples are numerous. Some suggestions are as follows:
a) Ice melting to water.
b) A match being struck produces a flame.
c) A shirt fading when exposed to light or too many washings.
2. There are three principal reasons for a non-scientist to study science.
a) Science influences society in very profound ways. In order to be able to make informed
and intelligent decisions about ethically complex problems like human cloning, genetic
engineering, or climate change, it is essential to have at least some understanding of the
workings of scientific principles.
b) Everyone has to some degree a responsibility in sustaining the variability of the planet for
future generations. Important decisions regarding science policy and funding are political
decisions generally made by nonscientists. An informed public can influence these
decisions and can help minimize the potential for misguided or perverted applications of
science by ignorant or evil governments.
c) Science can be described as a particular way to understand the workings of the world and
the universe. Lacking appreciation of scientific principles, an uninformed observer will
fail to appreciate completely the beauty, complexity and subtlety of nature. Learning
some of the basics of science leads to a deeper, richer, and more fulfilled life.
3.
a) The bright color of the rug is the result of particular molecules in the rug. When particles
of sunlight, photons, hit the rug, the bright color molecules are destroyed or altered in
some way.
b) Because water molecules are attracted to the salt crystals, the water breaks up the salt
crystals, and surrounds the individual particles of the salt, a process observed as
dissolving.
4. Chemistry is the science that investigates the molecular reason for the processes occurring in
our macroscopic world.
1
,Chapter 1 Instructor’s Manual
5. The scientific method involves first making observations of nature, from which patterns are
identified. From these patterns, broadly applicable generalizations called scientific laws are
established. A theory or model is then constructed to provide an interpretation of the
behavior of nature. The theory is then tested by further experiments and modified if
necessary to correct for any errors in the theory exposed by the experiments.
6. A law is a concise statement or equation that summarizes a great variety of observations,
while a theory explains the cause of the observations. A theory has been tested by experiment
over a length of time and has more predictive power than a law.
7. Science and art are similar mostly in their creativity and observations of the world. The
difference lies in what they do with their observations and how they are judged. Scientists
take their observations and create a model of reality that is judged by experimentation for its
validity. Artists observe the world and create a painting or sculpture that is judged by its
creativity and workmanship.
8. The Greek approach to scientific knowledge was through pure reason and intuition. Today
we approach science through experimentation.
9. Galileo Inquisition
Democritus Atomos
John Dalton The atomic theory
Andreas Vesalius Human anatomy
Empedocles Four basic elements
Joseph Proust Constant composition
Copernicus Sun-centered universe
Ernest Rutherford The nuclear atom
Thales All things are water
Lavoisier Conservation of mass
Boyle Criticized idea of four elements
10. The two main pursuits of alchemists were the transmutation of ordinary materials into gold
and the discovery of the “elixir of life”. Alchemists contributed to modern chemistry their
understanding of metals, specifically how metals combine to form alloys. Alchemists also
contributed laboratory separation and purification methods, including the isolation of natural
substances (pharmacological) used to treat various ailments.
11. The scientific revolution began in 1543, signaled by the publication of two books. The first
book by Copernicus announced his sun-centered universe theory. The second book by
Vesalius gave an accurate description of human anatomy. The reason these books mark the
beginning of the scientific revolution is the methods Copernicus and Vesalius used to learn
about the natural world – they both used observation instead of pure reason.
12. An element is a substance that cannot be separated into simpler substances by chemical
means. A compound can be separated into simpler substances by chemical means. All
compounds are made from two or more elements combined.
2
, Tro
The gas nitrogen and the metal gold are examples of elements; they cannot be separated into
anything simpler. Sugar and salt (sodium chloride) are examples of compounds; they can,
with more or less difficulty, be subdivided into their elements. Heating sugar in a pan is a
degree to that as one is left with a black carbonaceous deposit.
13. A pure substance cannot be separated into simpler substances by physical means, such as
filtration, chromatography, crystallization or distillation. A mixture consists of two or more
pure substances, and can be separated into those individual components by selection of the
appropriate physical methods.
The compounds sugar and sodium chloride in question 12 are examples of pure substances;
they cannot be further purified by any method. A mixture could be made by dissolving sugar
in water. We could recover the sugar simply by evaporating the water away. Another
example of a mixture is air, which is composed of several gases – nitrogen, oxygen etc.
14. A homogeneous mixture is completely uniform on the molecular scale. Air and a solution of
sugar in water are examples of homogeneous mixtures. Heterogeneous mixtures are not
uniform on a molecular scale. If sand is thrown into the solution of sugar, the sandy regions
are clearly distinguishable from the non-sandy ones.
15. The three states of matter are distinguished by the strength of the interactions between the
molecules relative to their thermal energy. (For the sake of brevity we will refer here only to
molecules, but it should be remembered that substances may be composed of atoms,
molecules or ions) The relative strength of the molecular interactions decreases in the
sequence solid – liquid – gas. In a solid, the interactions are strong enough to prevent free
movement of the molecules and they are locked into rigid arrangements (lattices). In a liquid,
the molecular energies are strong enough to loosen the grip of the intermolecular forces
sufficiently to allow free movement of molecules; but the intermolecular forces still maintain
enough control to keep the molecules together. In a gas, molecular energies have increased to
the extent that now all inter-molecular shackles are broken and gas molecules behave
completely independently. This molecular picture explains the obvious properties of solids,
liquids and gases. Solids are rigid and dense; liquids flow freely yet have a density similar to
the solid; gases have a very low density and are confined only by their container.
16.
a) Solid: incompressible, fixed volume, fixed shape
b) Liquid: incompressible, fixed volume, variable shape
c) Gas: compressible, variable shape, variable volume
17. John Dalton, using the laws of Lavoisier and Proust and the data from his own experiments,
combined a number of ideas to formulate the “atomic theory.” Dalton’s atomic theory was
based on three parts:
First, each element is composed of particles called atoms, which can neither be created
nor destroyed.
Second, all atoms of the same element have the same mass and other properties. These
properties are unique characteristics of each element, and thus differ from other elements.
3
, Chapter 1 Instructor’s Manual
Third, atoms of different types can combine to form compounds in simple whole number
ratios. For example, the compound carbon dioxide is formed from one carbon atom and
two oxygen atoms. The numbers, 1 and 2, are simple whole numbers.
18. Rutherford examined atomic structure through his gold foil experiment. By shooting alpha
particles at a thin sheet of gold foil, Rutherford tested his idea that atoms were either soft,
like blueberry muffins, or hard, like billiard balls. The results of his experiment were
surprising. The majority of particles passed though the gold foil without deflection (as
expected), but some deflected, scattering at angles both large and small. A small portion
bounced back in the direction they had come from.
19. The only way to explain the results of the gold foil experiment was to propose a new model
of the atom in which most of the atom must be empty space. This structure would allow most
of the alpha particles to pass through the gold foil with little or no deflection. However, the
atom must also contain a nucleus, a dense positively charged central core containing most of
the mass. In the experiment, whenever an alpha particle came close to a nucleus, or hit it
head on, it experienced a large repulsive force causing it to be scattered. Furthermore, since
the atom is electrically neutral, it must contain an equal number of negative charges
(electrons) and positive charges. The exact identity of the positive charge was later
established to be the proton. Rutherford purposed the electrons were outside the nucleus.
20. A black hole is a very dense form of matter where the structures of atoms have broken down,
to form “solid” matter. The large mass and small size associated with the black hole causes a
strong gravitational field, which allows mass and light to enter but not leave the black hole.
Thus, because black holes neither reflect nor emit light, they are referred to as “black”. If
atoms did not have their characteristic structure of a tiny dense nucleus surrounded by a large
volume of "empty" space, then all matter should have the enormous density of a black hole.
SOLUTIONS TO PROBLEMS:
21.
a) Water boiling and bubbles forming represent an observation. It would be made during an
experiment on heating water.
b) “Two grams of hydrogen combine with sixteen grams of oxygen to form eighteen grams
of water” represents an observation. It would be the result of one experiment.
c) “Chlorine and sodium readily combine in a chemical reaction that emits much heat and
light” is also an observation.
d) “The properties of elements vary periodically with the mass of their atoms” is a law. The
relationship between element properties and size statement was derived from examination
of many observations. It is often referred to as the periodic law.
4
MOLECULAR REASONS
ANSWERS TO QUESTIONS:
1. All natural phenomena in the world we can see are the result of invisible molecular
interactions.
Examples are numerous. Some suggestions are as follows:
a) Ice melting to water.
b) A match being struck produces a flame.
c) A shirt fading when exposed to light or too many washings.
2. There are three principal reasons for a non-scientist to study science.
a) Science influences society in very profound ways. In order to be able to make informed
and intelligent decisions about ethically complex problems like human cloning, genetic
engineering, or climate change, it is essential to have at least some understanding of the
workings of scientific principles.
b) Everyone has to some degree a responsibility in sustaining the variability of the planet for
future generations. Important decisions regarding science policy and funding are political
decisions generally made by nonscientists. An informed public can influence these
decisions and can help minimize the potential for misguided or perverted applications of
science by ignorant or evil governments.
c) Science can be described as a particular way to understand the workings of the world and
the universe. Lacking appreciation of scientific principles, an uninformed observer will
fail to appreciate completely the beauty, complexity and subtlety of nature. Learning
some of the basics of science leads to a deeper, richer, and more fulfilled life.
3.
a) The bright color of the rug is the result of particular molecules in the rug. When particles
of sunlight, photons, hit the rug, the bright color molecules are destroyed or altered in
some way.
b) Because water molecules are attracted to the salt crystals, the water breaks up the salt
crystals, and surrounds the individual particles of the salt, a process observed as
dissolving.
4. Chemistry is the science that investigates the molecular reason for the processes occurring in
our macroscopic world.
1
,Chapter 1 Instructor’s Manual
5. The scientific method involves first making observations of nature, from which patterns are
identified. From these patterns, broadly applicable generalizations called scientific laws are
established. A theory or model is then constructed to provide an interpretation of the
behavior of nature. The theory is then tested by further experiments and modified if
necessary to correct for any errors in the theory exposed by the experiments.
6. A law is a concise statement or equation that summarizes a great variety of observations,
while a theory explains the cause of the observations. A theory has been tested by experiment
over a length of time and has more predictive power than a law.
7. Science and art are similar mostly in their creativity and observations of the world. The
difference lies in what they do with their observations and how they are judged. Scientists
take their observations and create a model of reality that is judged by experimentation for its
validity. Artists observe the world and create a painting or sculpture that is judged by its
creativity and workmanship.
8. The Greek approach to scientific knowledge was through pure reason and intuition. Today
we approach science through experimentation.
9. Galileo Inquisition
Democritus Atomos
John Dalton The atomic theory
Andreas Vesalius Human anatomy
Empedocles Four basic elements
Joseph Proust Constant composition
Copernicus Sun-centered universe
Ernest Rutherford The nuclear atom
Thales All things are water
Lavoisier Conservation of mass
Boyle Criticized idea of four elements
10. The two main pursuits of alchemists were the transmutation of ordinary materials into gold
and the discovery of the “elixir of life”. Alchemists contributed to modern chemistry their
understanding of metals, specifically how metals combine to form alloys. Alchemists also
contributed laboratory separation and purification methods, including the isolation of natural
substances (pharmacological) used to treat various ailments.
11. The scientific revolution began in 1543, signaled by the publication of two books. The first
book by Copernicus announced his sun-centered universe theory. The second book by
Vesalius gave an accurate description of human anatomy. The reason these books mark the
beginning of the scientific revolution is the methods Copernicus and Vesalius used to learn
about the natural world – they both used observation instead of pure reason.
12. An element is a substance that cannot be separated into simpler substances by chemical
means. A compound can be separated into simpler substances by chemical means. All
compounds are made from two or more elements combined.
2
, Tro
The gas nitrogen and the metal gold are examples of elements; they cannot be separated into
anything simpler. Sugar and salt (sodium chloride) are examples of compounds; they can,
with more or less difficulty, be subdivided into their elements. Heating sugar in a pan is a
degree to that as one is left with a black carbonaceous deposit.
13. A pure substance cannot be separated into simpler substances by physical means, such as
filtration, chromatography, crystallization or distillation. A mixture consists of two or more
pure substances, and can be separated into those individual components by selection of the
appropriate physical methods.
The compounds sugar and sodium chloride in question 12 are examples of pure substances;
they cannot be further purified by any method. A mixture could be made by dissolving sugar
in water. We could recover the sugar simply by evaporating the water away. Another
example of a mixture is air, which is composed of several gases – nitrogen, oxygen etc.
14. A homogeneous mixture is completely uniform on the molecular scale. Air and a solution of
sugar in water are examples of homogeneous mixtures. Heterogeneous mixtures are not
uniform on a molecular scale. If sand is thrown into the solution of sugar, the sandy regions
are clearly distinguishable from the non-sandy ones.
15. The three states of matter are distinguished by the strength of the interactions between the
molecules relative to their thermal energy. (For the sake of brevity we will refer here only to
molecules, but it should be remembered that substances may be composed of atoms,
molecules or ions) The relative strength of the molecular interactions decreases in the
sequence solid – liquid – gas. In a solid, the interactions are strong enough to prevent free
movement of the molecules and they are locked into rigid arrangements (lattices). In a liquid,
the molecular energies are strong enough to loosen the grip of the intermolecular forces
sufficiently to allow free movement of molecules; but the intermolecular forces still maintain
enough control to keep the molecules together. In a gas, molecular energies have increased to
the extent that now all inter-molecular shackles are broken and gas molecules behave
completely independently. This molecular picture explains the obvious properties of solids,
liquids and gases. Solids are rigid and dense; liquids flow freely yet have a density similar to
the solid; gases have a very low density and are confined only by their container.
16.
a) Solid: incompressible, fixed volume, fixed shape
b) Liquid: incompressible, fixed volume, variable shape
c) Gas: compressible, variable shape, variable volume
17. John Dalton, using the laws of Lavoisier and Proust and the data from his own experiments,
combined a number of ideas to formulate the “atomic theory.” Dalton’s atomic theory was
based on three parts:
First, each element is composed of particles called atoms, which can neither be created
nor destroyed.
Second, all atoms of the same element have the same mass and other properties. These
properties are unique characteristics of each element, and thus differ from other elements.
3
, Chapter 1 Instructor’s Manual
Third, atoms of different types can combine to form compounds in simple whole number
ratios. For example, the compound carbon dioxide is formed from one carbon atom and
two oxygen atoms. The numbers, 1 and 2, are simple whole numbers.
18. Rutherford examined atomic structure through his gold foil experiment. By shooting alpha
particles at a thin sheet of gold foil, Rutherford tested his idea that atoms were either soft,
like blueberry muffins, or hard, like billiard balls. The results of his experiment were
surprising. The majority of particles passed though the gold foil without deflection (as
expected), but some deflected, scattering at angles both large and small. A small portion
bounced back in the direction they had come from.
19. The only way to explain the results of the gold foil experiment was to propose a new model
of the atom in which most of the atom must be empty space. This structure would allow most
of the alpha particles to pass through the gold foil with little or no deflection. However, the
atom must also contain a nucleus, a dense positively charged central core containing most of
the mass. In the experiment, whenever an alpha particle came close to a nucleus, or hit it
head on, it experienced a large repulsive force causing it to be scattered. Furthermore, since
the atom is electrically neutral, it must contain an equal number of negative charges
(electrons) and positive charges. The exact identity of the positive charge was later
established to be the proton. Rutherford purposed the electrons were outside the nucleus.
20. A black hole is a very dense form of matter where the structures of atoms have broken down,
to form “solid” matter. The large mass and small size associated with the black hole causes a
strong gravitational field, which allows mass and light to enter but not leave the black hole.
Thus, because black holes neither reflect nor emit light, they are referred to as “black”. If
atoms did not have their characteristic structure of a tiny dense nucleus surrounded by a large
volume of "empty" space, then all matter should have the enormous density of a black hole.
SOLUTIONS TO PROBLEMS:
21.
a) Water boiling and bubbles forming represent an observation. It would be made during an
experiment on heating water.
b) “Two grams of hydrogen combine with sixteen grams of oxygen to form eighteen grams
of water” represents an observation. It would be the result of one experiment.
c) “Chlorine and sodium readily combine in a chemical reaction that emits much heat and
light” is also an observation.
d) “The properties of elements vary periodically with the mass of their atoms” is a law. The
relationship between element properties and size statement was derived from examination
of many observations. It is often referred to as the periodic law.
4
