Relative Atomic Mass & Mass Spectrometry
Atoms are too small to weigh directly, so chemists use a relative scale with Carbon-12 as the standard. Mass spectrometry is the technique used to find the mass and abundance of an element’s isotopes, allowing us to calculate its average mass.
Relative Atomic Mass Analyzer
Select an element to see its mass spectrum and how its relative atomic mass (Ar) is calculated from the weighted average of its isotopes.
The Mole Concept
The mole is the chemist’s “dozen”—a unit that connects the macroscopic mass we can measure to the microscopic world of atoms and molecules. This section breaks down the key relationships.
Key Relationships
These two formulas are the foundation for all quantitative chemistry. They allow us to convert between mass, moles, and the number of particles.
Moles from Mass
n = m / M
n = moles, m = mass (g), M = molar mass (g/mol)
Particles from Moles
N = n × NA
N = particles, n = moles, NA = 6.02 x 1023
Mole Conversion Calculator
Practice converting mass to moles and particles for a common substance, glucose (C6H12O6). Enter a mass to begin.
180.16 g/mol
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Empirical & Molecular Formulas
Chemists determine a compound’s identity by first finding its empirical formula (the simplest whole-number ratio of atoms) from its percentage composition. If the molar mass is known, the true molecular formula can be found.
Empirical Formula Calculator
Enter the percentage composition of a compound to find its empirical formula. The calculator will walk you through the steps from the worked example for a compound containing C, H, and O.
Homologous Series
Organic compounds are classified into families called homologous series. Each series has a characteristic functional group that gives its members similar chemical properties. Click on a series to learn more.
IUPAC Nomenclature
The International Union of Pure and Applied Chemistry (IUPAC) provides a systematic set of rules for naming organic compounds, ensuring every molecule has a unique, unambiguous name. Test your skills below.
IUPAC Naming Practice
Name the molecule shown below, then check your answer. Use the “New Molecule” button to try another.
CH3-CH2-CH3
Alkane
Structural Isomers
Structural isomers are compounds that share the same molecular formula but have different structural formulas. This difference in atom connectivity gives them unique names and distinct physical properties.
Isomer Explorer
Select a molecular formula to see all its possible structural isomers for simple alkanes.
Polymer Basics: Addition Polymerisation
Polymers are macromolecules built from repeating monomer units. In addition polymerisation, unsaturated monomers (containing a C=C double bond) add to each other, breaking the double bond to form a long, saturated chain.
Polymerisation of Ethene
This animation shows how ethene monomers link up to form poly(ethene). The weak pi-bond in each double bond breaks to form new, strong sigma bonds between the monomers.
Structure and Properties of Polymers
The macroscopic properties of a polymer, like its rigidity and density, are a direct result of its molecular structure. The degree of chain branching is a key factor that chemists can control.
Polymer Property Comparator
Why is a milk bottle (HDPE) rigid while a plastic bag (LDPE) is flexible? Compare two common polymers to see how chain branching affects their properties.
Towards a Sustainable Future
The traditional “take-make-dispose” linear economy is unsustainable. The goal is to shift to a circular economy, which minimizes waste by keeping materials in use through reuse, repair, and recycling.
Linear vs. Circular Economy
Toggle between the models to visualize the flow of materials.
Take
Make
Use
Dispose
Recycle
The traditional path: resources are extracted, made into products, and then thrown away.
