Conservation of mass
The conservation of mass, also called the law of conservation of matter, is a principle in science. It says that when matter changes from one substance to another in a chemical change, or changes between solid, liquid and gas in a physical change, there is no detectable change in the total amount of matter.[1]
Mass and matter
The mass of an object measures how much matter it contains.[2]
Examples
The working of a battery is one everyday example of the conservation of matter.[3] The Chemistry 2e textbook notes that clear examples are not easy to find, because outside a laboratory people rarely collect all of the material produced in a change.[4]
Atoms in chemical reactions
In a chemical reaction, bonds between atoms break and form and the atoms are rearranged, but the total number of atoms of each element stays the same. A balanced chemical equation shows this.[5]
History
The French chemist Antoine Lavoisier (1743–1794) is often called the father of modern chemistry.[6] According to the Science History Institute, over about ten years he popularised the principle of conservation of mass, using experiments to show that matter is not created or destroyed, only changed.[7] Lavoisier argued that chemical changes could be studied by carefully weighing everything involved in a reaction, including the gases.[8]
Working with his collaborator and wife, Marie-Anne Paulze Lavoisier, he overturned the older phlogiston theory and showed that burning and breathing both need a newly isolated kind of air.[9] He showed that when a metal is heated in air, oxygen combines with it, so its mass increases.[10]
Limits
In nuclear processes, mass can be converted into energy. When an atom's nucleus forms from protons and neutrons, the atom has slightly less mass than its parts; this difference is called the mass defect.[11] The missing mass has been turned into energy that is given off as the atom forms.[12] The link between mass and energy is described by Albert Einstein's equation E = mc2.[13] When antimatter meets ordinary matter, both are destroyed and their mass becomes energy in the form of gamma rays.[14]
References
- ↑ Flowers, Paul; et al. (2019). "1.2 Phases and Classification of Matter". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
It states that there is no detectable change in the total quantity of matter present when matter converts from one type to another (a chemical change) or changes among solid, liquid, or gaseous states (a physical change).
- ↑ Flowers, Paul; et al. (2019). "1.2 Phases and Classification of Matter". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
The mass of an object is a measure of the amount of matter in it.
- ↑ Flowers, Paul; et al. (2019). "1.2 Phases and Classification of Matter". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
…the operation of batteries provide examples of the conservation of matter
- ↑ Flowers, Paul; et al. (2019). "1.2 Phases and Classification of Matter". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
Although this conservation law holds true for all conversions of matter, convincing examples are few and far between because, outside of the controlled conditions in a laboratory, we seldom collect all of the material that is produced during a particular conversion.
- ↑ Flowers, Paul; et al. (2019). "21.2 Nuclear Equations". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
A balanced chemical reaction equation reflects the fact that during a chemical reaction, bonds break and form, and atoms are rearranged, but the total numbers of atoms of each element are conserved and do not change.
- ↑ "Antoine-Laurent Lavoisier". Scientific Biographies. Science History Institute. Retrieved 18 October 2026.
Known as the father of modern chemistry, Antoine Lavoisier (1743–1794) sought to bring order to the field of chemistry.
- ↑ "Antoine-Laurent Lavoisier". Scientific Biographies. Science History Institute. Retrieved 18 October 2026.
Over the course of a decade, Lavoisier popularized the principle of conservation of mass, demonstrating through experiment that matter can neither be created nor destroyed, only transformed.
- ↑ "Antoine-Laurent Lavoisier". Scientific Biographies. Science History Institute. Retrieved 18 October 2026.
By carefully weighing all components in a chemical reaction, including the gasses, he argued that one could analyze chemical transformations in accordance with the principle of the conservation of mass.
- ↑ "Antoine-Laurent Lavoisier". Scientific Biographies. Science History Institute. Retrieved 18 October 2026.
Together with his scientific collaborator and wife Marie-Anne Paulze Lavoisier , he upended the so-called phlogiston theory, establishing that both combustion and respiration required a newly isolated type of air.
- ↑ "Antoine-Laurent Lavoisier". Scientific Biographies. Science History Institute. Retrieved 18 October 2026.
Lavoisier showed instead that oxygen combined with the metal, increasing its mass.
- ↑ Flowers, Paul; et al. (2019). "21.1 Nuclear Structure and Stability". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
This difference between the calculated and experimentally measured masses is known as the mass defect of the atom.
- ↑ Flowers, Paul; et al. (2019). "21.1 Nuclear Structure and Stability". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
The loss in mass accompanying the formation of an atom from protons, neutrons, and electrons is due to the conversion of that mass into energy that is evolved as the atom forms.
- ↑ Flowers, Paul; et al. (2019). "21.1 Nuclear Structure and Stability". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
The conversion between mass and energy is most identifiably represented by the mass-energy equivalence equation as stated by Albert Einstein
- ↑ Flowers, Paul; et al. (2019). "21.2 Nuclear Equations". Chemistry 2e. OpenStax. Retrieved 18 October 2026.
When antimatter encounters ordinary matter, both are annihilated and their mass is converted into energy in the form of gamma rays