CEM 141 215 Exam Questions with 100% Complete
Solutions
What is the difference between atoms and molecules?
Atoms are basic particles that compose ordinary matter. Molecules are what atoms become when
they bind together in specific geometrical arrangements. Atom is the smallest particle in an
element. Molecules are formed by the combination of two or more atoms. Unlike atoms,
molecules can be subdivided to individual atoms. The atoms are bonded together in a molecule.
An atom has a nucleus surrounded by electrons. The electrons are negatively charged particules
and the nucleus contains neutrons and positively charged protons.
Distinguish between the 3 states of matter: solid, liquid, gas
Gases, liquids and solids are all made up of atoms, molecules and ions.
1) Liquid - they are packed close together like solids, but have a weaker attraction allowing them
to move. Liquids have a fixed volume, but not a fixed shape, and take the shape of their
container. Ex: water alcohol, and gasoline are liquids at room temp.
2) Solid - They are packed close to each other in a fixed location due to their strong attraction to
one another. A solid has a fixed volume and a rigid shape.
3) Gas - he attraction between particles is very weak allowing them to move freely and at a large
distance before colliding with one another. Due to the large amount of space between the
particles, gases are compressible. Gases always assume the shape and volume of their container.
Ex: helium, nitrogen, and carbon dioxide at room temp.
Differentiate between mixtures and pure substances
,Matter can be broken down into two categories: pure substances and mixtures. Pure substances
are further broken down into elements and compounds. Mixtures are physically combined
structures that can be separated into their original components. A chemical substance is
composed of one type of atom or molecule.
1) Mixture - Substance composed of two or more particles in proportions that can vary from one
sample to another
2) Pure Substance - made up of only one type of particle and its composition does not vary from
one sample to the other. Particles that compose a pure substance can be individual atoms or a
group of atoms joined together.
Ex: helium b/c it's made up of helium atoms; water is made up of water molecules; and sodium
chloride is made up of sodium chloride units.
Differentiate between elements and compounds
1. Element: substance that cannot be chemically broken down into simpler substances.
2. Compound: substance that is composed of two or more elements.
A compound contains atoms of different elements chemically combined together in a fixed ratio.
An element is a pure chemical substance made of same type of atom.
Differentiate between heterogeneous and homogeneous mixtures
1. Heterogeneous Mixture: composition varies from one region of the mixture to another. They
don't mix uniformly.
2. Homogeneous Mixture: have same composition throughout. They mix uniformly.
I know the SI base units for length, mass, time and temperature
,Meter (m) = Length
Kilogram (kg) = Mass
Second (s) = Time
Kelvin (K) = Temperature
Importance of reporting correct units with measurements
Without units, the results are unclear and it is hard to keep track of what each separate
measurement entails. Units of measurement are the terms that we use to describe the size of
something. You probably know that units include things like seconds, kilograms, meters, and so
forth.
Without standard units of measurement, scientists would have a huge problem understanding
what other scientists were saying.
What unit system do scientists use?
The International System of Units (SI).
Law of Conservation of Mass and who created it
Antoine Lavoisier said "in a chemical reaction, matter is neither created nor destroyed". The total
mass of the substances involved in the reaction does not change.
Radioactivity
The emission of elementary particles by some atoms when their unstable nuclei disintegrate (see
half-life). Materials composed of such atoms are radioactive. (See alpha radiation, beta radiation,
and gamma radiation.)
Nucleus
, nucleus is the positively charged center of the atom consisting of protons and neutrons.
Proton
A positively charged particle within a nucleus ... The number of protons in an element's nucleus
is called the atomic number.
Neutron
Neutral partials witching a nucleus. They contain no electrical charge
subatomic particle found in the nucleus of atoms that differs from the other subatomic particles
(called "protons") in the nucleus of atoms because neutrons have no (zero) charge whereas each
proton has a positive charge of +1.
Atomic Mass Unit
AMU - 1/12 of the mass of a carbon -12 atom
it is a unit of mass used to express atomic masses and molecular masses.
Atomic Number
The number of protons in a atom's nucleus and is given the symbol Z
Chemical Symbol
an abbreviation of a chemical element, symbols in a periodic table
Isotope
An atom that has the same number of protons but different number of neutrons
What is a mass number and the symbol represents it?
Solutions
What is the difference between atoms and molecules?
Atoms are basic particles that compose ordinary matter. Molecules are what atoms become when
they bind together in specific geometrical arrangements. Atom is the smallest particle in an
element. Molecules are formed by the combination of two or more atoms. Unlike atoms,
molecules can be subdivided to individual atoms. The atoms are bonded together in a molecule.
An atom has a nucleus surrounded by electrons. The electrons are negatively charged particules
and the nucleus contains neutrons and positively charged protons.
Distinguish between the 3 states of matter: solid, liquid, gas
Gases, liquids and solids are all made up of atoms, molecules and ions.
1) Liquid - they are packed close together like solids, but have a weaker attraction allowing them
to move. Liquids have a fixed volume, but not a fixed shape, and take the shape of their
container. Ex: water alcohol, and gasoline are liquids at room temp.
2) Solid - They are packed close to each other in a fixed location due to their strong attraction to
one another. A solid has a fixed volume and a rigid shape.
3) Gas - he attraction between particles is very weak allowing them to move freely and at a large
distance before colliding with one another. Due to the large amount of space between the
particles, gases are compressible. Gases always assume the shape and volume of their container.
Ex: helium, nitrogen, and carbon dioxide at room temp.
Differentiate between mixtures and pure substances
,Matter can be broken down into two categories: pure substances and mixtures. Pure substances
are further broken down into elements and compounds. Mixtures are physically combined
structures that can be separated into their original components. A chemical substance is
composed of one type of atom or molecule.
1) Mixture - Substance composed of two or more particles in proportions that can vary from one
sample to another
2) Pure Substance - made up of only one type of particle and its composition does not vary from
one sample to the other. Particles that compose a pure substance can be individual atoms or a
group of atoms joined together.
Ex: helium b/c it's made up of helium atoms; water is made up of water molecules; and sodium
chloride is made up of sodium chloride units.
Differentiate between elements and compounds
1. Element: substance that cannot be chemically broken down into simpler substances.
2. Compound: substance that is composed of two or more elements.
A compound contains atoms of different elements chemically combined together in a fixed ratio.
An element is a pure chemical substance made of same type of atom.
Differentiate between heterogeneous and homogeneous mixtures
1. Heterogeneous Mixture: composition varies from one region of the mixture to another. They
don't mix uniformly.
2. Homogeneous Mixture: have same composition throughout. They mix uniformly.
I know the SI base units for length, mass, time and temperature
,Meter (m) = Length
Kilogram (kg) = Mass
Second (s) = Time
Kelvin (K) = Temperature
Importance of reporting correct units with measurements
Without units, the results are unclear and it is hard to keep track of what each separate
measurement entails. Units of measurement are the terms that we use to describe the size of
something. You probably know that units include things like seconds, kilograms, meters, and so
forth.
Without standard units of measurement, scientists would have a huge problem understanding
what other scientists were saying.
What unit system do scientists use?
The International System of Units (SI).
Law of Conservation of Mass and who created it
Antoine Lavoisier said "in a chemical reaction, matter is neither created nor destroyed". The total
mass of the substances involved in the reaction does not change.
Radioactivity
The emission of elementary particles by some atoms when their unstable nuclei disintegrate (see
half-life). Materials composed of such atoms are radioactive. (See alpha radiation, beta radiation,
and gamma radiation.)
Nucleus
, nucleus is the positively charged center of the atom consisting of protons and neutrons.
Proton
A positively charged particle within a nucleus ... The number of protons in an element's nucleus
is called the atomic number.
Neutron
Neutral partials witching a nucleus. They contain no electrical charge
subatomic particle found in the nucleus of atoms that differs from the other subatomic particles
(called "protons") in the nucleus of atoms because neutrons have no (zero) charge whereas each
proton has a positive charge of +1.
Atomic Mass Unit
AMU - 1/12 of the mass of a carbon -12 atom
it is a unit of mass used to express atomic masses and molecular masses.
Atomic Number
The number of protons in a atom's nucleus and is given the symbol Z
Chemical Symbol
an abbreviation of a chemical element, symbols in a periodic table
Isotope
An atom that has the same number of protons but different number of neutrons
What is a mass number and the symbol represents it?
