Name: mole, mass, and avogadro’s number
Uploaded: 2020-09-03T13:38:25.000Z
Duration: 1 min 54 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Chemistry

Matter and its Interactions

PS.Chm.2.1

Molar Mass

The periodic table gives the average atomic mass of each atom. However, macroscopic samples contain extremely large numbers of atoms. Therefore, it is essential to use a counting unit called Avogadro&#39;s number.

Avogadro&rsquo;s number, expressed as the symbol NA, is usually rounded to 6.022 &times; 1023. Its value is equal to the number of atoms in exactly 12 grams of pure carbon-12 isotope.

The term mole, abbreviated mol, is used to describe Avogadro&#39;s number, just as the familiar term, dozen, is used to describe an amount of 12.

Nonetheless, a dozen of different items can weigh differently despite having the same number of items.&nbsp;Similarly, moles of different elements have different masses but always contain the same number of atoms.&nbsp;

The mass in grams of one mole of an element is called the molar mass, expressed in grams per mole. Its value is numerically equivalent to the element&rsquo;s atomic mass. Hence, the definition of the mole lets us count particles by weighing them. The molar mass and Avogadro&#39;s number can be used as conversion factors.

This can be used to calculate the number of atoms in a 5 gram bar of gold. The average molar mass of gold is 196.96 g/mol. So, to convert the mass into moles, divide the mass of the bar by the average molar mass.&nbsp;Then, multiply the number of moles by&nbsp;Avogadro&#39;s number to get the number of total atoms in the sample. So, this bar of gold contains 1.529 &times; 1022&nbsp;atoms.

molar mass

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, water, H2O, and hydrogen peroxide, H2O2, are alike in that their respective molecules are composed of hydrogen and oxygen atoms. However, because a hydrogen peroxide molecule contains two oxygen atoms, as opposed to the water molecule, which has only one, the two substances exhibit very different properties.

Atoms and molecules are extremely small. Therefore, for measuring their macroscopic amounts, a standard scientific unit is needed. The mole is an amount unit similar to familiar units like pair, dozen, gross, etc. It provides a specific measure of the number of atoms or molecules in a sample of matter. The Latin connotation for the word &ldquo;mole&rdquo; is &ldquo;large mass&rdquo; or &ldquo;bulk,&rdquo; which is consistent with its use as the name for this unit. The mole provides a link between an easily measured macroscopic property, bulk mass, and an extremely important fundamental property, number of atoms, molecules, and so forth.

A mole of a substance is that amount in which there are 6.02214076 &times; 1023 discrete entities (atoms or molecules). This large number conveniently rounded to 6.022 &times;&nbsp;1023, is a fundamental constant known as Avogadro&rsquo;s number (NA) or the Avogadro constant in honor of Italian scientist Amedeo Avogadro. This constant is properly reported with an explicit unit of &ldquo;per mole&rdquo;.

Consistent with its definition as an amount unit, 1 mole of any element contains the same number of atoms as 1 mole of any other element. The masses of 1 mole of different elements, however, are different, since the masses of the individual atoms are drastically different. The molar mass of an element (or compound) is the mass in grams of 1 mole of that substance, a property expressed in units of grams per mole (g/mol).

The molar mass of any substance is numerically equivalent to its atomic or formula weight in amu. Per the amu definition, a single carbon atom weighs 12 amu (its atomic mass is 12 amu). A mole of carbon weighs 12 g (12 g C = 1 mol C atoms = 6.022 &times; 1023 C atoms), and the molar mass of carbon is 12 g/mol. This relationship holds for all elements since their atomic masses are measured relative to that of the amu-reference substance, carbon-12. Extending this principle, the molar mass of a compound in grams is likewise numerically equivalent to its formula mass in amu. For example, helium has an atomic mass of 4.002 amu and a molar mass of 4.002 g/mol.

While atomic mass and molar mass are numerically equivalent, keep in mind that they are vastly different in terms of scale. To appreciate the enormity of the mole, consider a small drop of water weighing about 0.03 g. Although this represents just a tiny fraction of 1 mole of water (~18 g), it contains more water molecules than can be imagined. If the molecules were distributed equally among the roughly seven billion people on earth, each person would receive more than 100 billion molecules of water.

The mole defines the relationship between mass and the number of atoms. This allows the number of atoms to be calculated based using suitable forms of the conversion factor: 1 mole of atoms = 6.022 &times; 1023 atoms. To convert between the mass of an element (in grams) and the number of moles, the molar mass of the element (g/mol) is used as a conversion factor.

Text adapted from <a href="https://openstax.org/books/chemistry-2e/pages/3-1-formula-mass-and-the-mole-concept">Openstax Chemistry 2e, Section 3.1: Formula Mass and the Mole Concept.</a>

The identity of a substance is defined not only by the types of atoms or ions it contains but by the quantity of each type of atom or ion. For example, ...

Education

JoVE Core

Atoms and Elements

KEY TERMS AND CONCEPTS

mole, mass, and avogadro’s number

The mole links mass and the number of particles in a substance. It gives chemists a standard way to count atoms and molecules in samples that are far too small to see. It also helps show why substances with the same kinds of atoms can still have very different properties, like water, H2O, and hydrogen peroxide, H2O2.

The mole is an amount unit, like a pair or a dozen. One mole contains 6.02214076 × 10^23 discrete entities, such as atoms or molecules. This number is usually rounded to 6.022 × 10^23 and is called Avogadro’s number, or the Avogadro constant, named for Amedeo Avogadro. The constant is written with the unit per mole.

One mole of any element contains the same number of atoms as one mole of any other element. The masses are different, though, because atoms have different individual masses. That is why one mole of one element does not weigh the same as one mole of another element.

Molar mass is the mass in grams of one mole of a substance. It is reported in grams per mole, or g/mol. The molar mass of an element or compound is numerically equal to its atomic mass or formula mass in amu. For example, carbon has an atomic mass of 12 amu, so 1 mole of carbon has a mass of 12 g and a molar mass of 12 g/mol.

This same relationship works for other elements and for compounds. Helium, for example, has an atomic mass of 4.002 amu and a molar mass of 4.002 g/mol. Although the numbers match, atomic mass and molar mass are very different in scale.

A tiny drop of water can still contain an enormous number of molecules. A drop that weighs about 0.03 g is only a small part of 1 mole of water, which is about 18 g. Even so, it holds more water molecules than can easily be imagined. If those molecules were shared equally among the roughly seven billion people on Earth, each person would still get more than 100 billion molecules of water.

The mole also lets scientists convert between mass and amount. Using the relationship 1 mole of atoms = 6.022 × 10^23 atoms, the number of atoms can be calculated from a sample. The molar mass of an element is also used as a conversion factor to move between grams and moles.

Mole, Mass, and Avogadro’s Number

the atomic theory of matter

Dalton’s Laws and Early Atomic Ideas

Dalton’s atomic theory explains matter with atoms, elements, and compounds. It also shows how chemical changes follow simple laws. This idea gave chemistry a microscopic model for what can be seen in the lab. The earliest recorded ideas about matter came from ancient Greek philosophers. Leucippus and Democritus said all matter was made of tiny, finite particles called atomos, meaning “indivisible.” Aristotle and others later argued that matter was made from four elements: fire, earth, air, and...

subatomic particles

Atomic Structure: Protons, Neutrons, and Electrons

Atomic structure is built from three subatomic particles: protons, neutrons, and electrons. Atoms make up all matter, and these particles explain an atom’s mass and charge. The electron was first identified at the end of the 19th century by J.J. Thomson. He used a cathode ray tube, a sealed glass tube with almost all the air removed and two metal electrodes. When high voltage was applied, a visible beam called a cathode ray formed. The beam bent toward positive charge and away from negative...

elements: chemical symbols and isotopes

Reading Element Symbols and Isotope Notation

Chemical symbols and isotope notation help identify elements and their atoms. A chemical symbol is an abbreviation for an element or a single atom of that element. Mercury, for example, is written as Hg. The same symbol can point to one atom in the microscopic domain or to many atoms of the element in a container or sample. Many symbols come from the element’s common English name. Others come from Latin, Greek, or German names. Aluminum uses Al, while iron uses Fe from the Latin word Ferrum.

ions and ionic charges

Predicting Ion Charges on the Periodic Table

Ion charges can often be predicted from an element’s position on the periodic table. In chemical reactions, the nucleus stays unchanged, but electrons may be transferred, lost, or shared. When atoms gain or lose electrons during compound formation, they become ions, which are electrically charged particles. A positive ion is called a cation. A cation has more protons than electrons because it lost electrons. A negative ion is called an anion. An anion has more electrons than protons because it...

the periodic table

Periodic Table Patterns and Element Groups

The periodic table organizes elements by repeating patterns in their properties. Chemists first noticed that some elements behaved alike, so they grouped them by chemical behavior. Lithium, sodium, and potassium are one example. They are shiny and conduct heat and electricity well. Calcium, strontium, and barium form another group with similar physical and chemical properties. Yet these two groups are not the same. The lithium group is much more reactive, and its elements form oxygen compounds...

atomic mass

Average Atomic Mass and Isotopes

Average atomic mass explains why many elements on the periodic table have decimal values. Atoms are extremely small, so scientists use the atomic mass unit, or amu, to measure them. A carbon atom weighs less than 2 × 10−23 g, and the amu is defined from carbon-12. One amu is exactly 1/12 the mass of one carbon-12 atom, which is 1.6605 × 10−24 g. The dalton (Da) and the unified atomic mass unit (u) mean the same thing as the amu. For a single atom, atomic mass is usually close to its mass...

The mole links mass and the number of particles in a substance. It gives chemists a standard way to count atoms and molecules in samples that are far too small to see. It also helps show why substances with the same kinds of atoms can still have very different properties, like water, H2O, and hydrogen peroxide, H2O2. The mole is an amount unit, like a pair or a dozen. One mole contains 6.02214076 × 10^23 discrete entities, such as atoms or molecules. This number is usually rounded to 6.022 ×...

key terms and concepts

Learn how the mole connects mass, atoms, and molecules through Avogadro’s number and molar mass, with clear examples for high school chemistry.

Mole, Mass, and Avogadro’s Number | JoVE K12

chemistry

JoVE Core Chemistry brings general chemistry concepts to life using concise and easy-to-understand animated video lessons. Plus, in the scientist-in-action videos, we demonstrate classical and original research experiments performed in today's laboratories worldwide.

PS.Chm.4.3

PS.Chm.4.4

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Structure And Properties Of Matter

Quantifying matter

Interactions Of Matter

Stoichiometry

Virginia  Standards of Learning

HIgh School

CH.2

CH.2.a

CH.4

CH.4.a

Physical Science

PS.4

PS.4.a

Arizona Science Standards

High School

HS+C.P1

HS+C.P1U1.7

Texas Essential Knowledge and Skills

CHEM.8

CHEM.8.A

CHEM.11

CHEM.11.E

Alabama Course of Study Science

Matter and Its Interactions

9-12.C.1.1

Florida Department of Education

SC.912.P.8

SC.912.P.8.9

Chemistry and Physics

IPC.7

IPC.7.A

Georgia Standards of Excellence

SC3.

The Mole Concept and Avogadro’s Number

Scientific Laws and Theories

Scientific Laws

In science, a law is defined as a concise, verbal or mathematical, statement that summarizes a vast number of experimental observations. ...

The Scientific Method

Chemistry is an empirical science. Scientists often pose questions to understand the chemistry in everyday life and seek answers to these questions. To ...

Classifying Matter by State

Chemistry is the study of matter and the changes it undergoes. Matter is anything that has mass and occupies space. Matter is all around us; the air, ...

Classifying Matter by Composition

Matter: Pure Substances and Mixtures
According to its composition, the matter can be classified into two broad categories &mdash; pure substances and ...

The Atomic Theory of Matter

The earliest recorded discussion of the basic structure of matter comes from ancient Greek philosophers. Leucippus and Democritus argued that all matter ...

Subatomic Particles

Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller ...

Elements: Chemical Symbols and Isotopes

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is ...

Use models to explain how the scientific understanding of atomic structure has evolved.

PS.Chm.1.1

Radioactivity and Nuclear Equations

Nuclear chemistry is the study of reactions that involve changes in nuclear structure. The nucleus of an atom is composed of protons and, except for ...

Types of Radioactivity

The most common types of radioactivity are &#945; decay, &#946; decay, &#947; decay, neutron emission, and electron capture.
Alpha (&#945;) decay is the ...

Nuclear Stability

Protons and neutrons, collectively called nucleons, are packed together tightly in a nucleus. With a radius of about 10&#8722;15 meters, a nucleus is ...

Nuclear Binding Energy

The difference between the calculated and experimentally measured masses is known as the mass defect of the atom. In the case of helium-4, the mass defect ...

Radioactive Decay and Radiometric Dating

Radioactivity is a spontaneous disintegration of an unstable nuclide and is a random process, as all the nuclei in the sample do not decay simultaneously. ...

Nuclear Fission

Many heavier elements with smaller binding energies per nucleon can decompose into more stable elements that have intermediate mass numbers and larger ...

Nuclear Power

Controlled nuclear fission reactions are used to generate electricity. Any nuclear reactor that produces power via the fission of uranium or plutonium by ...

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process ...

Nuclear Transmutation

Nuclear transmutation is the conversion of one nuclide into another. It can occur by the radioactive decay of a nucleus, or the reaction of a nucleus with ...

Use models to compare nuclear reactions including alpha decay, beta decay and gamma decay; nuclear fusion and nuclear fission.

PS.Chm.1.2

Atomic Orbitals

An atomic orbital represents the three-dimensional regions in an atom where an electron has the highest probability to reside. The radial distribution ...

The Pauli Exclusion Principle

The arrangement of electrons in the orbitals of an atom is called its electron configuration. We describe an electron configuration with a symbol that ...

The Energies of Atomic Orbitals

In an atom, the negatively charged electrons are attracted to the positively charged nucleus. In a multielectron atom, electron-electron repulsions are ...

The Aufbau Principle and Hund's Rule

To determine the electron configuration for any particular atom, we can build the structures in the order of atomic numbers. Beginning with hydrogen, and ...

electron-configuration-of-multielectron-atoms

Electron Configuration of Multielectron Atoms

The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the ...

Use models to explain how electrons are distributed in atoms.

PS.Chm.1.3

Periodic Classification of the Elements

The periodic table arranges atoms based on increasing atomic number so that elements with the same chemical properties recur periodically. When their ...

The Periodic Table

As early chemists discovered more elements, they realized that various elements could be grouped by their similar chemical behaviors. One such grouping ...

Atomic Mass

Atoms &mdash; and the protons, neutrons, and electrons that compose them &mdash; are extremely small. For example, a carbon atom weighs less than 2 ...

Use the Periodic Table as a model to predict the relative properties of elements based on the pattern of valence electrons in the outermost energy levels of atoms.

atomic-radii-and-effective-nuclear-charge

Atomic Radii and Effective Nuclear Charge

The elements in groups of the periodic table exhibit similar chemical behavior. This similarity occurs because the members of a group have the same number ...

Ionic Radii

Ionic radius is the measure used to describe the size of an ion. A cation always has fewer electrons and the same number of protons as the parent atom; it ...

Ionization Energy

The amount of energy required to remove the most loosely bound electron from a gaseous atom in its ground state is called its first ionization energy ...

Electron Affinity

The electron affinity (EA) is the energy change for adding an electron to a gaseous atom to form an anion (negative ion).



This process can be either ...

Construct an explanation to infer the atomic size, reactivity, electronegativity, and ionization energy of an element based on its position in the Periodic Table.

PS.Chm.2.2

Types of Chemical Bonds

Chemical bonding theories were pioneered by American chemist Gilbert&#xA0;N. Lewis. He developed a model called the Lewis model to explain the type and ...

Lewis Symbols and the Octet Rule

Chemical bonds are complex interactions between two or more atoms or ions, which reduce the potential energy of the molecule. Gilbert N. Lewis developed a ...

Ionic Bonding and Electron Transfer

Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence ...

The Born-Haber Cycle

Lattice Energy&#xA0;

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a ...

trends-in-lattice-energy-ion-size-and-charge

Trends in Lattice Energy: Ion Size and Charge

An ionic compound is stable because of the electrostatic attraction between its positive and negative ions. The lattice energy of a compound is a measure ...

Covalent Bonding and Lewis Structures

Compared to ionic bonds, which results from the transfer of electrons between metallic and nonmetallic atoms, covalent bonds result from the mutual ...

Electronegativity

Whether a bond is nonpolar or polar covalent is determined by a property of the bonding atoms called electronegativity.&#xA0;

Electronegativity values of ...

bond-polarity-dipole-moment-and-percent-ionic-character

Bond Polarity, Dipole Moment, and Percent Ionic Character

Bond Polarity

The absolute value of the difference in electronegativity (&Delta;EN) of two bonded atoms provides a rough measure of the polarity to be ...

lewis-structures-of-molecular-compounds-and-polyatomic-ions

Lewis Structures of Molecular Compounds and Polyatomic Ions

To draw Lewis structures for complicated molecules and molecular ions, it is helpful to follow a step-by-step procedure as outlined:


	Determine the ...

Resonance

The Lewis structure of a nitrite anion (NO2&minus;) may actually be drawn in two different ways, distinguished by the locations of the N-O and N=O ...

Formal Charges

In some cases, there are seemingly more than one valid Lewis structures for molecules and polyatomic ions. The concept of formal charges can be used to ...

Exceptions to the Octet Rule

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules fall into three categories:


	...

Bond Energies and Bond Lengths

Stable molecules exist because covalent bonds hold the atoms together. The strength of a covalent bond is measured by the energy required to break it, ...

Analyze and interpret data to explain the mechanisms and properties of the two main types of intramolecular (ionic and covalent) bonds.

PS.Chm.3.1

molecular-comparison-of-gases-liquids-and-solids

Molecular Comparison of Gases, Liquids, and Solids

Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no ...

Intermolecular vs Intramolecular Forces

Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular ...

Intermolecular Forces

Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions ...

comparing-intermolecular-forces-melting-point-boiling-point

Comparing Intermolecular Forces: Melting Point, Boiling Point, and Miscibility

Intermolecular forces are attractive forces that exist between molecules. They dictate several bulk properties, such as melting points, boiling points, ...

surface-tension-capillary-action-and-viscosity

Surface Tension, Capillary Action, and Viscosity

Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded ...

Hydrogen Bonds

Hydrogen BondsHydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, ...

Van der Waals Interactions

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions ...

Construct an explanation to summarize the influences intermolecular forces have on the properties of chemical compounds.

PS.Chm.3.2

Molecules and Compounds

Atoms and Molecules

Everything in the universe is made up of matter, and matter is composed of a combination of elements. An atom is the smallest unit of ...

Chemical Formulas

A chemical formula presents information about the proportions of atoms constituting a particular chemical compound or molecule, mainly using symbols of ...

Use models to predict chemical names and formulas including ionic (binary & ternary), acidic, and binary covalent compounds.

PS.Chm.3.3

Analyze the structure of atoms and isotopes.

Mole, Mass, and Avogadro’s Number

Description

Transcript

Tags

More videos by Standards