Chemistry is classified as a physical science. Both the U.S. Department of Education and the National Science Foundation place chemistry squarely within the physical sciences category, alongside physics, astronomy, and earth sciences. That said, chemistry has deep ties to the biological sciences, and several of its subfields sit right at the boundary between the two.
What Makes a Science “Physical” or “Biological”
The distinction comes down to what you’re studying. Physical sciences focus on nonliving (abiotic) systems: rocks, minerals, energy, forces, atoms, chemical reactions. Biological sciences focus on living (biotic) systems: animals, plants, microorganisms, and how they function. Chemistry, at its core, is the study of matter’s composition, properties, and transformations. It deals with atoms, molecules, and energy transfer. Those are nonliving things, which is why chemistry falls on the physical science side of the line.
Physics, chemistry, astronomy, and earth science make up the traditional physical sciences. Biology, ecology, zoology, and botany make up the life sciences. In the U.S. Department of Education’s Classification of Instructional Programs, chemistry and all its subfields (organic, inorganic, analytical, theoretical, polymer, forensic, and environmental chemistry) are listed under code 40: Physical Sciences.
Why Chemistry Feels Biological
If you’ve taken a chemistry class that involved DNA, proteins, or cell membranes, you might wonder why chemistry is grouped with physics rather than biology. The reason is that chemistry isn’t studying living organisms. It’s studying the molecules those organisms are made of, which is a different question entirely.
Carbon is the clearest example of this overlap. All life on Earth is carbon-based. Proteins, DNA, carbohydrates, and fats are all built on carbon atom frameworks. Organic chemistry studies carbon-containing compounds, and many of those compounds happen to be the building blocks of living things. But organic chemistry itself is still a physical science. It’s concerned with how carbon bonds form, break, and rearrange, not with how an organism grows or reproduces.
Where Chemistry Meets Biology
The boundary between physical and biological science isn’t a wall. It’s more like a gradient, and chemistry sits closer to that boundary than almost any other physical science. Several hybrid fields exist in the overlap zone.
Biochemistry studies the chemical processes that happen inside living systems: how enzymes catalyze reactions, how cells convert food into energy, how DNA replicates. Chemical biology flips that relationship, using chemical tools and techniques to manipulate and study biological systems, like designing small molecules that can switch specific biological processes on or off. Both fields draw equally from chemistry, cell biology, molecular biology, and biophysics. Yale’s Department of Molecular, Cellular, and Developmental Biology describes them as spanning all four disciplines simultaneously.
The discovery of DNA’s double helix structure is a good illustration of why this boundary matters less than people think. That breakthrough came from a biologist and a physicist working together, applying physical science principles (specifically, X-ray crystallography) to a biological molecule. A National Academies report on the intersection of these fields notes that the fundamental principles governing living matter are most likely to be discovered right at the interface of biology with physics and information theory.
How This Plays Out in School and College
In most high school and college curricula, chemistry is taught as a physical science. You’ll typically find it in the same department or course sequence as physics. When universities list their degree programs, chemistry degrees sit under physical sciences.
That said, if you pursue chemistry far enough, you’ll encounter subfields that blur the line. Physical chemistry uses thermodynamics and mathematical models to predict how chemical reactions behave, which is firmly on the physics side. Biochemistry and molecular biology pull strongly toward the life sciences. The NSF groups chemistry under “Physical sciences and earth sciences” for funding and reporting purposes, but interdisciplinary programs like “Biological and Physical Sciences” exist as their own category under multidisciplinary studies.
If you’re choosing courses to fulfill a physical science requirement, a general chemistry class will almost always count. If you need a biological science credit, it won’t, even though you might spend a week learning about amino acids and proteins.
The Practical Reality
Chemistry’s physical science classification reflects its foundations: the study of atoms, molecules, energy, and reactions. But modern chemistry increasingly operates across the traditional boundary. Clinical biochemistry laboratories, for example, use physical chemistry techniques like mass spectrometry and polymerase chain reaction technology to diagnose diseases, detect gene variations, and analyze metabolic disorders. The chemistry is physical. The application is biological.
So the short answer to “Is chemistry a physical or biological science?” is that it’s a physical science by formal classification, by how universities categorize it, and by how funding agencies track it. But it’s also the physical science most deeply intertwined with biology, and some of the most active areas of modern research exist in that overlap. If you’re drawn to both, fields like biochemistry and chemical biology let you work in both worlds at once.