Water freezing is a physical change. 1 It involves the transition of water from a liquid state to a solid state without any alteration in its chemical composition. The freezing process is reversible, 2 and the water molecules retain their chemical identity as H2O throughout the phase change.
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Key Takeaways: Is Water Freezing a Physical or Chemical Change?
- Water freezing is a physical change because it involves a change in the state of the substance without altering its chemical composition.
- During water freezing, the water molecules lose energy and rearrange themselves into a more ordered, crystalline structure.
- Water freezing is not a chemical change because it does not involve any chemical reactions or the formation of new substances.
Why is water freezing a physical change?
Water freezing is considered a physical change because it involves a change in the state or phase of the substance without altering its chemical composition or identity. 3 When water freezes, it transitions from a liquid state to a solid state, forming ice. The process of freezing involves the rearrangement of water molecules, which slow down and form a more ordered, crystalline structure.
During freezing, the water molecules lose energy, and their kinetic energy decreases. As a result, the attractive forces between the water molecules become stronger, causing them to come closer together and form a lattice-like structure characteristic of ice.
However, the individual water molecules remain the same, consisting of two hydrogen atoms bonded to one oxygen atom (H2O).
Since no new substances are formed during the freezing process and the chemical composition of water remains unchanged, it is classified as a physical change.
Other examples of physical changes include boiling, melting, condensation, and sublimation, all of which involve alterations in the physical properties of a substance without affecting its chemical composition.
Why is water freezing not a chemical change?
Water freezing is not a chemical change because it does not involve any chemical reactions or the formation of new substances. In a chemical change, the composition and identity of the substance(s) involved are altered, resulting in the formation of new chemical compounds. 4
When water freezes, the water molecules reorganize themselves into a more ordered structure, but the fundamental composition of the molecules remains the same.
The freezing process is driven by the intermolecular forces between water molecules and the reduction of their kinetic energy, causing them to transition from a liquid state to a solid state.
Chemical changes, on the other hand, involve the breaking and forming of chemical bonds, resulting in the creation of new substances with different chemical properties.
Examples of chemical changes include combustion, oxidation, and decomposition reactions, where the original substances are transformed into new compounds.
Since water freezing does not involve any chemical reactions or the creation of new substances, it is classified as a physical change rather than a chemical change.
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- 3.6: Changes in Matter – Physical and Chemical Changes. (2019, September 3). Chemistry LibreTexts. https://chem.libretexts.org/Courses/University_of_British_Columbia/CHEM_100%3A_Foundations_of_Chemistry/03%3A_Matter_and_Energy/3.06%3A_Changes_in_Matter_-_Physical_and_Chemical_Changes
- Reversible process (thermodynamics) – Wikipedia. (2020, November 2). Reversible Process (Thermodynamics) – Wikipedia. https://en.wikipedia.org/wiki/Reversible_process_(thermodynamics)
- Foundation, C. (n.d.). CK12-Foundation. CK12-Foundation. https://flexbooks.ck12.org/cbook/ck-12-middle-school-physical-science-flexbook-2.0/section/2.8/primary/lesson/physical-change-ms-ps/
- Changes in Matter: Physical vs. Chemical Changes. (n.d.). Changes in Matter: Physical Vs. Chemical Changes. https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes