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Physical change

A physical change is a transformation in matter that alters its physical properties, such as shape, size, density, or state of matter, without affecting its chemical composition or identity.^[1] These changes typically involve rearrangements of particles or energy transfers that do not break or form chemical bonds, allowing the original substance to be recovered unchanged.^[2] Common examples include the melting of ice into water, the evaporation of liquid water into vapor, and the crushing or cutting of a solid object like wood.^[3] Unlike chemical changes, which produce new substances with different molecular structures through reactions, physical changes are generally reversible and do not involve alterations to the atomic or molecular makeup of the material.^[4] For instance, boiling water represents a physical change because the H₂O molecules remain intact, merely transitioning from liquid to gas phase, whereas burning wood initiates a chemical change by forming new compounds like carbon dioxide and ash.^[5] Physical changes often occur in response to temperature, pressure, or mechanical force, and they play a fundamental role in natural processes, such as the water cycle, and industrial applications like material processing.^[6] Key characteristics of physical changes include the conservation of mass, no breaking or forming of chemical bonds (though energy may be absorbed or released due to intermolecular forces during phase transitions), and the retention of the substance's chemical identity, including traits like solubility and conductivity.^[7] Examples extend to everyday phenomena, such as dissolving sugar in water—where the sugar can be recovered by evaporation—or the expansion of metals under heat, both of which highlight how physical changes facilitate phase transitions without altering the fundamental nature of the matter involved.^[8] Understanding physical changes is essential in fields like thermodynamics and materials science, as they underpin phenomena from weather patterns to manufacturing techniques.^[9]

Definition and Fundamentals

Definition

A physical change is a transformation in the form or physical properties of a substance that does not alter its chemical composition or identity.^[1] Such changes affect attributes like state, shape, size, or texture while preserving the fundamental makeup of the material.^[2] At its core, matter consists of atoms and molecules, the basic units that define a substance's properties and behavior.^[10] In a physical change, the atomic and molecular structure remains intact, ensuring no new substances are formed and the original identity of the matter is maintained.^[4] This preservation distinguishes physical alterations as rearrangements or reconfigurations at the macroscopic level without breaking or forming chemical bonds.^[11] Physical changes are often reversible, allowing the substance to return to its original form through appropriate conditions.^[12]

Key Characteristics

Physical changes are characterized by their reversibility, meaning that in most cases, the original state of the substance can be restored by reversing the conditions that induced the change, such as refreezing melted ice to return it to a solid form.^[13] This reversibility stems from the fact that physical changes involve alterations in the form or arrangement of matter without affecting its fundamental identity.^[14] A defining feature of physical changes is the conservation of mass and energy, where the total mass of the matter remains constant before and after the change, as no atoms are created or destroyed.^[15] This principle, rooted in Antoine Lavoisier's law of conservation of mass formulated in 1789, applies equally to physical processes, ensuring that the quantity of matter is preserved even as its physical state or structure varies.^[16] Energy conservation similarly holds, with any absorbed or released energy facilitating the change without altering the material's composition.^[17] Unlike chemical changes, physical changes do not involve breaking or forming chemical bonds, thereby lacking an energy barrier that would modify the molecular composition of the substance.^[13] This absence of bond alterations means that the chemical identity of the matter persists, with changes limited to intermolecular interactions or spatial arrangements.^[18] These changes are observable and measurable through shifts in physical properties such as density, volume, or texture, all while the underlying chemical composition remains unchanged.^[19] For instance, the volume of a substance may increase during expansion due to heating, allowing direct quantification of the transformation without any alteration to its elemental makeup.^[13] Such metrics provide empirical evidence of the change's occurrence and extent, emphasizing the non-compositional nature of physical transformations.

Distinction from Chemical Change

Core Differences

A chemical change is defined as a process that alters the chemical composition of a substance, resulting in the formation of new substances through the breaking and forming of chemical bonds.^[3] In contrast, a physical change does not modify the chemical identity of the substance, preserving its molecular structure while only altering its physical state or form.^[4] At the process level, physical changes primarily involve alterations to intermolecular forces, which are the attractions between molecules, such as those governing phase transitions or shape modifications without disrupting the internal bonding within molecules. Chemical changes, however, entail intramolecular reactions that affect the bonds within molecules, leading to a reconfiguration of atoms into distinct chemical entities.^[20] This distinction underscores that physical changes operate on weaker, reversible interactions between molecules, whereas chemical changes require overcoming stronger covalent or ionic bonds. Detection of physical changes typically relies on observing reversible shifts in properties like density, volume, or appearance, which can often be undone by adjusting conditions such as temperature or pressure.^[21] For chemical changes, identification involves confirming the formation of irreversible new compounds, frequently through spectroscopic techniques that reveal alterations in molecular signatures, such as shifts in absorption or emission spectra.^[22] Regarding energy implications, physical changes commonly involve the absorption or release of latent heat associated with phase transitions, representing the energy needed to overcome intermolecular forces without initiating bond rearrangements.^[23] Chemical changes, by comparison, necessitate activation energy to surmount the energy barrier for bond breaking and forming, enabling the reaction pathway to proceed and often resulting in a net energy change reflected in the reaction enthalpy.^[24]

Illustrative Comparisons

One illustrative comparison between physical and chemical changes is the melting of ice versus the burning of wood. When ice melts, it undergoes a physical change by transitioning from a solid to a liquid state while retaining its chemical composition as H₂O, and the process is reversible by freezing the water back into ice. In contrast, burning wood represents a chemical change where the cellulose and other compounds in the wood react with oxygen to produce new substances such as carbon dioxide, water vapor, and ash, resulting in an irreversible transformation. Another paired example is dissolving sugar in water compared to the reaction of sodium with water. Dissolving sugar creates a physical change, forming a uniform solution where sugar molecules disperse throughout the water without altering their chemical identity, and the sugar can be recovered by evaporating the water.^[25] Conversely, sodium reacting with water is a chemical change, as the sodium metal vigorously displaces hydrogen ions to produce sodium hydroxide and hydrogen gas, forming entirely new compounds that cannot be reverted to the original sodium.^[26] A common misconception arises with processes like cooking, which may appear as mere physical alterations in texture or appearance but often involve chemical changes, such as the denaturation and cross-linking of proteins in an egg when heated, producing a substance with different chemical properties. To distinguish between physical and chemical changes in a laboratory setting, simple tests can be applied: for physical changes like mixtures, filtration or evaporation can separate components without altering their identity, whereas chemical changes are indicated by reactivity tests, such as observing gas evolution or precipitate formation that signals new substance creation.^[27] In physical changes, the law of conservation of mass holds strictly, as the total mass remains unchanged before and after the process.^[28]

Types of Physical Changes

Phase Transitions

Phase transitions represent fundamental physical changes in which matter shifts between states—solid, liquid, or gas—without altering its chemical composition. These transformations occur as a result of variations in temperature and pressure, which influence the strength and balance of intermolecular forces holding particles together. For instance, increasing temperature provides kinetic energy to overcome these forces, allowing particles to move more freely and transition to a less ordered state.^[29]^[30] The primary types of phase transitions include melting, where a solid converts to a liquid; freezing, the reverse process from liquid to solid; vaporization, or evaporation, transforming a liquid to a gas; condensation, shifting gas back to liquid; sublimation, direct conversion from solid to gas; and deposition, the opposite from gas to solid. Each type is reversible under appropriate conditions, maintaining the substance's molecular identity throughout. These processes are endothermic when absorbing heat to increase disorder (melting, vaporization, sublimation) and exothermic when releasing heat to form more ordered structures (freezing, condensation, deposition).^[31]^[32] A prominent example is the water cycle, where evaporation (vaporization) occurs as liquid water absorbs solar energy and turns into water vapor, rising into the atmosphere without changing its H₂O composition. Subsequently, condensation forms liquid water droplets in clouds as the vapor cools, again preserving the molecular structure. This cycle demonstrates how phase transitions drive natural phenomena while keeping chemical identity intact.^[33]^[34]^[31] Energy involvement in phase transitions is quantified through latent heat, the energy absorbed or released per unit mass during the change without a temperature shift. The heat Q required is given by the equation

Q = m L

where m is the mass of the substance and L is the specific latent heat (of fusion for solid-liquid transitions or vaporization for liquid-gas transitions). For water, the latent heat of fusion is approximately 334 J/g, and that of vaporization is about 2260 J/g at standard conditions, highlighting the greater energy needed for gas formation due to stronger intermolecular disruption.^[23]^[31]

Mechanical and Structural Changes

Mechanical and structural changes encompass modifications to a material's form, dimensions, or internal organization while preserving its chemical identity and phase. These transformations occur through external forces or environmental conditions that reposition particles without inducing molecular-level reactions. Unlike phase transitions, they do not involve alterations in molecular motion driven by temperature or pressure; instead, they focus on macroscopic or microscopic rearrangements that affect observable traits such as texture or geometry./03:_Matter_and_Energy/3.06:Changes_in_Matter-_Physical_and_Chemical_Changes) Key types of these changes include cutting, crushing, bending, stretching, and crystallization. Cutting divides a solid into smaller segments using shear force, as seen when paper is sliced into strips, resulting in pieces that retain the original cellulose composition.^[35] Crushing applies compressive stress to reduce particle size, exemplified by pulverizing rock salt into finer grains, where the sodium chloride formula remains unchanged.^[2] Bending deforms materials like metal rods under flexural load, altering curvature without compositional shift, while stretching elongates elastic substances such as rubber through tensile pull, increasing length but not molecular bonds.^[36] Crystallization forms highly ordered lattices from supersaturated solutions or melts, such as sodium chloride precipitating into cubic crystals from evaporated seawater, organizing ions into a periodic structure without new substances./Physical_Properties_of_Matter/Solutions_and_Mixtures/Case_Studies/RECRYSTALLIZATION) The underlying processes rely on mechanical force application for shape alterations, which disrupts intermolecular arrangements but spares covalent or ionic bonds, requiring only kinetic energy for repositioning rather than activation energy for reactions. In crystallization, controlled cooling or solvent evaporation promotes nucleation and growth of crystal facets, driven by thermodynamic favorability for lower-energy ordered states. These mechanisms ensure reversibility in many cases, such as reshaping bent wire or redissolving crystals, underscoring the absence of chemical bond involvement.^[37] Illustrative examples highlight retention of identity: breaking a glass pane shatters it into shards that are chemically identical silica-based fragments, useful for demonstrating increased surface area without loss of material essence. Alloy formation via non-reactive mixing, like blending molten copper (88%) and tin (12%) to create bronze, yields a homogeneous solid solution that enhances mechanical strength through atomic substitution rather than compound formation. Such changes influence physical properties, including expanded surface area from cutting or crushing—which can accelerate dissolution rates in subsequent processes—and altered density from stretching, yet the substance remains recoverable by physical means, with total mass conserved as per fundamental principles./06%3A_Structures_and_Energetics_of_Metallic_and_Ionic_solids/6.07%3A_Alloys_and_Intermetallic_Compounds/6.7A%3A_Substitutional_Alloys)^[2]

Dissolution and Mixtures

Dissolution refers to the process by which a solute disperses uniformly throughout a solvent to form a homogeneous mixture, known as a solution, without undergoing a chemical reaction. This physical change occurs primarily through intermolecular attractions between solute and solvent particles, where the solute-solute and solvent-solvent interactions are overcome by stronger or comparably strong solute-solvent forces, leading to the solute particles becoming surrounded by solvent molecules. For instance, when sodium chloride (NaCl) is added to water, the ionic bonds in the salt lattice break due to interactions with water's polar molecules, resulting in Na⁺ and Cl⁻ ions dispersing evenly, but the ions retain their identity without forming new substances.^[38]^[39]^[40] Mixtures formed through dissolution or simple combination can be classified as homogeneous or heterogeneous based on the uniformity of their composition. Homogeneous mixtures, or solutions, appear uniform throughout and include examples like saltwater, where the solute is fully dissolved and not visible as separate particles. In contrast, heterogeneous mixtures display distinct phases or components that are not uniformly distributed, such as sand mixed with water, where the sand settles and can be observed separately. These mixtures do not involve chemical bonding between components, allowing the original substances to be recovered unchanged through physical means.^[39]^[41] Solubility, the maximum amount of solute that can dissolve in a given solvent under specific conditions, is a key factor in dissolution and is significantly influenced by temperature and pressure. For most solid solutes, solubility increases with rising temperature as more energy facilitates the breaking of solute-solute attractions, whereas for gases, solubility typically decreases with higher temperatures but increases with greater pressure according to Henry's law. In the case of NaCl(aq), the dissolved state represents a physical dispersion of ions, with no covalent bonds forming or new compounds created, emphasizing that dissolution is reversible and non-reactive.^[42]^[43]^[44] Heterogeneous and homogeneous mixtures can be separated using physical techniques that exploit differences in properties like particle size, volatility, or solubility, without altering the chemical identity of the components. Filtration effectively separates insoluble solids from liquids in heterogeneous mixtures, such as removing sand from water by passing the mixture through a filter. For homogeneous mixtures, distillation separates components based on boiling point differences, vaporizing and condensing the more volatile substance, while chromatography divides mixtures by differential adsorption onto a stationary phase as they move through a mobile phase, useful for complex solutions. These methods underscore the reversible nature of physical changes in mixtures.^[45]^[46]^[47]

Applications and Examples

Everyday Phenomena

Physical changes are integral to numerous routine activities encountered in daily life, where matter alters its form or state without changing its fundamental composition. For instance, when ice cubes are added to a beverage, they gradually melt into liquid water due to the surrounding warmth, transitioning from a solid to a liquid phase while remaining H₂O throughout the process.^[4] This phase transition is observable as the drink cools initially before reaching equilibrium, illustrating a reversible physical change that enhances refreshment without altering the drink's chemical makeup.^[5] Another common mechanical physical change occurs when tearing a sheet of paper, which simply alters its size and shape by breaking the physical bonds holding the fibers together, without producing any new substances.^[48] Similarly, stirring cream into coffee creates a homogeneous mixture, where the cream disperses evenly through the liquid, changing the appearance and texture to a lighter, blended consistency, yet the components—coffee and cream—retain their original identities and can theoretically be separated.^[49] Sensory experiences often highlight these transformations, such as the visible lightening of color when diluting paint with water, where the pigment particles spread out in a larger volume, reducing intensity without any molecular rearrangement.^[4] This dilution effect is purely physical, as the paint's composition stays the same, allowing for easy reversal by concentrating it again. Recognizing such changes fosters an understanding of non-compositional alterations in matter, which supports safer home practices by identifying reversible processes like these over those involving potential hazards. Seasonal weather patterns provide further relatable examples, including the melting of accumulated snow into liquid water as temperatures rise, a phase change that replenishes groundwater without chemical alteration.^[50] Likewise, water in roadside puddles evaporates under sunlight, shifting from liquid to vapor and disappearing from view, yet the water molecules persist in the atmosphere, ready to condense elsewhere.^[51] These natural occurrences underscore the ubiquity of physical changes, connecting abstract concepts to tangible environmental shifts.

Industrial and Scientific Uses

In industrial applications, physical changes play a central role in processes like distillation for oil refining, where crude oil is separated into fractions through phase transitions involving vaporization and condensation based on differing boiling points. This atmospheric distillation, the primary step in most refineries, heats crude oil to around 350–400°C, allowing lighter hydrocarbons to vaporize and rise in a fractionation tower, where they condense at various heights to yield products such as gasoline, kerosene, and diesel without altering the chemical composition of the molecules.^[52]^[53] Similarly, mechanical changes occur in metal forging, a manufacturing technique that deforms solid metals under compressive forces from hammers, presses, or rolls to achieve desired shapes, enhancing grain structure and strength through plastic deformation rather than chemical alteration. This process is widely used for producing durable components like automotive parts and aircraft fittings, minimizing material waste compared to subtractive methods.^[54] In scientific contexts, crystallization serves as a key physical change for purifying compounds, as seen in sugar production where supersaturated sucrose solutions are cooled to form pure crystals, separating the sugar from impurities like molasses based on solubility differences. This reversible process allows for high-purity output in the food industry, with crystals harvested via centrifugation and the mother liquor recycled, avoiding chemical reagents. In pharmacology, physical mixtures enable drug formulations by blending active pharmaceutical ingredients with excipients such as binders or diluents, creating uniform tablets or capsules without chemical reactions, which ensures stability and controlled release while leveraging solubility properties for bioavailability.^[55]^[56] The efficiency of these physical changes stems from their reversibility, which reduces waste and costs in industrial operations by allowing material recovery and reuse, unlike irreversible chemical processes that generate byproducts requiring disposal. For instance, in refining and purification, recycled streams lower energy demands and environmental impact, contributing to sustainable manufacturing practices.^[57] In modern technologies, cooling via refrigeration cycles exploits phase transitions in the vapor-compression system, where refrigerants undergo evaporation to absorb heat and condensation to release it, enabling efficient temperature control in food preservation and HVAC without chemical decomposition.^[58] Alloy mixing further demonstrates this through physical blending of metals in solid-state processes like mechanical alloying, which refines microstructure to yield stronger materials—such as high-strength steels—for aerospace applications, preserving elemental integrity without reactions.^[59]^[60]

Specialized Cases

One specialized case of physical change involves the temporary magnetization of ferromagnetic materials, such as iron filings exposed to an external magnetic field. In this process, the magnetic domains within the iron align with the applied field, resulting in a net magnetization that attracts the filings into patterns visualizing the field lines; this alignment is reversible upon removal of the field or through demagnetization techniques like heating or mechanical shock, without altering the material's chemical composition.^[61]^[62] Changes in optical properties represent another category of specialized physical changes, exemplified by the fogging of glass surfaces due to condensation. When humid air contacts a cold glass, water vapor undergoes a phase transition to liquid droplets, increasing the optical density and scattering light to create a translucent or opaque appearance; this effect is purely physical, as the water molecules retain their identity and can evaporate back to vapor upon warming.^[34]^[63] Similarly, the sublimation of dry ice (solid carbon dioxide) demonstrates a direct solid-to-gas transition under atmospheric conditions, producing a visible fog of condensed water vapor from the surrounding air without melting into a liquid intermediate, altering only the phase while preserving molecular structure.^[64] Certain alloys exhibit physical magnetism through domain alignment without chemical alteration, such as in iron-nickel compositions where ferromagnetism arises from the collective spin orientation of electrons in the lattice, enabling applications like temporary electromagnets.^[65]^[66] In gem formation, crystallization processes further illustrate specialized physical changes, where minerals like corundum (ruby and sapphire) or peridot solidify from cooling magmas or hydrothermal solutions into ordered crystal lattices, enhancing optical and mechanical properties through structural organization alone.^[67]^[68] These specialized cases remain classified as physical changes provided there is no alteration in chemical composition or electron transfer between atoms, distinguishing them from chemical reactions that involve bond formation or breakage.^[63] For instance, while magnetic domain alignment in alloys may involve electron spin reorientation, it does not result in new substances, maintaining the original atomic makeup.^[65]

Historical and Conceptual Development

Early Observations

The earliest recognitions of physical changes emerged in ancient philosophical frameworks, where observable transformations in matter were interpreted through qualitative observations rather than systematic experimentation. In the 4th century BCE, Aristotle proposed a theory of four elements—earth, water, air, and fire—each characterized by pairs of qualities such as hot/cold and wet/dry, to explain natural phenomena including changes in state.^[69] He described evaporation as a process where water, being cold and moist, could be heated by the sun to transform into air-like vapor, as detailed in his Meteorology, where moisture from the earth is drawn upward and contributes to atmospheric cycles without altering the fundamental substance.^[70] These ideas framed physical changes as alterations in elemental qualities rather than distinct processes, influencing Western thought for centuries.^[69] During the medieval period, Islamic scholars refined these concepts within alchemical traditions, distinguishing observable mixtures and dissolutions from the elusive goal of transmutation. In the 11th century, Avicenna (Ibn Sina) critiqued alchemical claims of metallic transformation while documenting practical changes, such as the dissolution of substances into their "first matter" through processes like putrefaction involving heat and moisture.^[71] He noted that mixing perfect bodies like gold with imperfect ones does not elevate the latter to perfection, emphasizing instead reversible dissolutions where substances could be reduced and reformed without essential change, as in the conjunction of body and spirit leading to a spiritual state that could be recongealed.^[71] These observations highlighted distinctions between mere mixing—preserving component identities—and purported transmutations, laying groundwork for empirical scrutiny of physical alterations.^[71] Pre-modern metallurgical practices provided hands-on evidence of physical changes through repeated observations of phase transitions in metalworking. In Bronze Age societies around 3000–1200 BCE, artisans noted the melting of copper and tin alloys in crucibles at high temperatures, followed by controlled cooling to achieve solidification into tools and ornaments, as evidenced by slag remnants and casting molds from sites across Europe and the Near East.^[72] These processes involved pouring molten metal, which solidified upon cooling—termed "freezing" in later terminology—demonstrating reversible state changes without loss of material identity, a key insight in early alloy production.^[73] Boiling observations occurred in fluxing liquids used to purify ores, where effervescence and vaporization aided separation, underscoring practical utility of such changes in refining techniques.^[72] The transition to modern science in the 17th century marked a shift toward empiricism, explicitly separating physical changes from alchemical mysticism through controlled experiments. Robert Boyle, in his 1661 work The Sceptical Chymist, rejected traditional alchemical principles like the tria prima (salt, sulfur, mercury) in favor of a corpuscular philosophy, arguing that changes like dissolution or evaporation were mechanical rearrangements of particles rather than qualitative transmutations.^[74] Influenced by the Royal Society's emphasis on observation and replication, Boyle's experiments—such as sublimating sulfur from solid to gas and back—demonstrated reversible physical alterations, paving the way for chemistry as a distinct empirical discipline.^[74] This empiricist approach formalized the recognition of physical changes as predictable, non-destructive processes, distinct from the speculative goals of alchemy.^[74]

Modern Understanding

In the late 18th century, Antoine Lavoisier formulated the law of conservation of mass, demonstrating that the total mass remains unchanged during physical processes such as melting, boiling, or dissolution, as no matter is created or destroyed.^[28] This principle, verified through precise weighings in closed systems, laid a foundational quantitative basis for distinguishing physical changes from speculative alchemical transformations.^[75] Building on this, John Dalton's atomic theory in the early 19th century provided a microscopic explanation, asserting that atoms are indivisible units that retain their identity in physical changes, involving only rearrangements of position or state without bond formation or breakage.^[76] Dalton's framework solidified the core differences between physical and chemical changes by emphasizing atomic integrity.^[77] The 20th century brought sophisticated thermodynamic models to analyze phase transitions, central to physical changes like solidification or vaporization. Josiah Willard Gibbs introduced the phase rule in 1876, expressed as F = C - P + 2, where F represents the degrees of freedom (variables like temperature and pressure that can be independently varied), C the number of independent components, and P the number of coexisting phases in equilibrium.^[78] This invariant relation predicts the constraints on multi-phase systems, such as the invariant triple point of water where solid, liquid, and vapor coexist at a fixed temperature and pressure.^[79] Such models enabled precise mapping of phase diagrams, informing industrial processes and theoretical predictions of stability under varying conditions. Advancements in the late 20th and early 21st centuries have leveraged nanotechnology to achieve controlled mechanical changes, such as reversible deformations in nanomaterials without chemical alteration. For example, carbon nanotubes and graphene composites exhibit tunable elasticity and strength at the nanoscale, allowing engineered physical responses like shape recovery in response to external stimuli.^[80] Concurrently, molecular dynamics simulations have elucidated the kinetics of dissolution at the atomic scale, modeling how solute molecules or ions separate and hydrate in solvents through intermolecular forces alone. These computations, often using force fields to track trajectories over picoseconds, reveal mechanisms like the stepwise disassembly of salt nanocrystals in water, confirming dissolution as a purely physical dispersion.^[81] Physical changes intersect with environmental science in contemporary climate modeling, where phase transitions like glacial ice melt drive global impacts. Thermodynamic simulations of ice sheet ablation under warming oceans quantify mass loss rates, projecting contributions to sea level rise from processes such as surface melting and basal sliding.^[82] This integration highlights how physical changes amplify feedback loops, such as reduced albedo accelerating further melt in polar regions.^[83]

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https://web.njit.edu/~kebbekus/analysis/4CHROMAT.htm
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Chemical Separations
Mixtures can also be separated by gas-phase chromatography, which takes advantage of the relative affinity of the different components in a mixture for the ...
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Chromatography - NJIT
Chromatography, a group of methods for separating very small quantities of complex mixtures ... Gas chromatography is the most widely used separation technique.
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[PDF] 5th Grade Title of Lesson: Chemical and Physical Changes Stations ...
a. Investigate physical changes by separating mixtures and manipulating (cutting, tearing, folding) paper to demonstrate examples of physical change.
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Chemical Reaction or Mixture? | K-12 Engineering - WordPress at UD |
A mixture is created when two or more different substances are physically combined and can be separated back into its original substances. Examples of mixtures ...
[52]
[PDF] Physical vs. Chemical Change
Directions: Compare the characteristics of physical and chemical change, then answer the question below. Is snow melting a physical or chemical change?
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[PDF] Examples Of Physical Change
about changes in matter and see how physical changes of matter compare to chemical changes. Study physical change vs. chemical change examples and processes.
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Oil and Petroleum Products Explained: Refining Crude Oil - EIA
Feb 22, 2023 · All refineries have atmospheric distillation units, but more complex refineries may have vacuum distillation units.
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The Process of Crude Oil Refining | EME 801
Distillation involves the separation of materials based on differences in their volatility. This is the first and most basic step in the refining process, and ...
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Smithy Secrets: An Intro to Forging Methods
### Summary: Metal Forging as a Physical Change in Manufacturing
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Pharmaceutical Formulation - StatPearls - NCBI Bookshelf - NIH
Pharmaceutical formulation is the multistep process where the active drug is mixed with all other components by considering the factors of particle size, ...
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Mixtures – Knowledge and References - Taylor & Francis
A mixture is a combination of two or more substances that are incorporated together without undergoing a chemical reaction. The physical properties of each ...
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[PDF] Serious Reduction of Hazardous Waste - Princeton University
the chemical nature of the waste did not change. If a waste is not totally eliminated, however, actions taken to reduce waste may also change the chemical ...
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The Vapor Compression Refrigeration Cycle, Step By Step - ARANER
Because of these changes, the refrigerant leaves the throttle valve as a liquid vapor mixture, typically in proportions of around 75 % and 25 % respectively.Missing: physical | Show results with:physical
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Mechanical Alloying: A Novel Technique to Synthesize Advanced ...
Mechanical alloying is a solid-state powder processing technique that involves repeated cold welding, fracturing, and rewelding of powder particles in a ...
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Metals & Alloys - The Chemistry of Art
The Stone Age first gave way briefly to the Copper Age around 4000 BC, before being replaced by the Bronze Age around 3600 BC, when the alloying of copper with ...
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[PDF] Nanotechnology and Magnetism - Vanderbilt University
The wand magnet and lodestone are permanent magnets. The iron filings, paper clips and iron oxide powder (in the vial) are temporary magnets. Tell students that ...
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Magnetic Field Lines Don't Really Exist | Physics Van
Jun 28, 2014 · Magnetic field lines are visual aids, not physical. The clumping seen in experiments is due to iron filings acting as dipoles, not the field ...
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[PDF] 4 Chemical and Physical Changes - CSUN
For example, when hydrogen gas and oxygen gas are heated the hydrogen gas burns and water is formed. This chemical change can be represented by the following ...
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1.14: Phase Transitions – Melting, Boiling, and Subliming
Phase Transitions (Phase Changes). Substances can change their physical phase, or state, often because of a temperature change.Missing: driven | Show results with:driven
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The Feynman Lectures on Physics Vol. II Ch. 36: Ferromagnetism
The phenomenon is called ferromagnetism. In paramagnetic and diamagnetic materials the induced magnetic moments are usually so weak that we don't have to worry ...
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[PDF] Magnetic Properties of Metals and Alloys. - andrew.cmu.ed
This chapter introduces metals and alloys used for soft and hard magnets. Alloy de- velopment illustrates the materials paradigm of synthesis → structure → ...
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Gems Formed in Magmatic Rocks - GIA
Gems form in magmatic rocks through cooling and solidification from igneous magmas, and examples include sanidine feldspar, peridot, and zircon.
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Geology of Corundum and Emerald Gem Deposits: A Review - GIA
Jan 31, 2020 · The corundum formed by direct crystallization from the melt as an accessory mineral phase. In volcanic rocks, sapphire and occasionally ruby ...Missing: physical | Show results with:physical
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Philosophy of Chemistry
Mar 14, 2011 · Aristotle used this elemental theory to account for many properties of substances. For example he distinguished between liquids and solids by ...
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Meteorology by Aristotle - The Internet Classics Archive
At first, they say, the earth was surrounded by moisture. Then the sun began to dry it up, part of it evaporated and is the cause of winds and the turnings back ...
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Treatise of Avicenna - | Alchemy Books and Texts Celestial Archive
In the third I will speak of the conjunction of body and spirit and the dissolution of the stone into the first matter. In the fourth I will speak of the ...
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A Latin text in which Medieval Author Avicenna discusses On Alchemy, with an introduction by scholar Dimitri Gutas.
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[PDF] Ancient and Historic Metals - Getty Museum
Lins reassesses the evidence for the formation of some of these corrosion products based on new research reported here. Looking at the corrosion of ...
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Vere Gordon Childe archive. The Bronze Age, 1930
The slag and unburnt charcoal is thereupon raked off, and the metal dragged out in lumps when on the point of solidifying.The cakes of raw metal from European “ ...
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Robert Boyle - Stanford Encyclopedia of Philosophy
Jan 15, 2002 · Best known today as the father of chemistry, Robert Boyle (1627–1691) has, since the early 1990s, emerged as a significant figure in early ...
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[PDF] Conservation of Mass - MIT OpenCourseWare
In the 18th century, Antoine Lavoisier, a French scientist, showed that there is no overall change in mass when a reaction takes place in a sealed container.
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Dalton's atomic theory (article) | Khan Academy
In the fourth and final part of Dalton's atomic theory, he suggested that chemical reactions don't destroy or create atoms. They merely rearranged the atoms.
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4.6: Dalton's Atomic Theory - Chemistry LibreTexts
Mar 20, 2025 · Atoms cannot be subdivided, created, or destroyed. Atoms of different elements can combine in simple whole number ratios to form chemical ...
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6.8: Gibbs' Phase Rule - Chemistry LibreTexts
Jul 7, 2024 · The phase rule applies to equilibrium systems in which any component can move freely between any two phases in which that component is present.
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Gibbs' Phase Rule: Where it all Begins - SERC (Carleton)
Aug 8, 2007 · Gibbs' Phase Rule provides the theoretical foundation, based in thermodynamics, for characterizing the chemical state of a (geologic) system.
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Nanotechnology: A Revolution in Modern Industry - PMC - NIH
Jan 9, 2023 · Nanotechnology offers useful alterations in the physiochemical, mechanical, magnetic, electrical, and optical properties of computing materials ...
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Molecular Dynamics Simulation of NaCl Dissolution
Feb 21, 2015 · Molecular dynamics simulations are used to investigate the dissolution of NaCl nanocrystals (containing ∼2400 ions) in water.Introduction · II Models and Methods · IV Summary and Conclusions · References
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Climate Change Indicators: Ice Sheets | US EPA
The most evident impact observed to date is a loss of ice due to warmer air and ocean waters. Warmer air causes the ice to melt more quickly and flow more ...
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Ice Sheets - Earth Indicator - NASA Science
Sep 25, 2025 · The ice sheets are melting due to the warming of Earth's atmosphere and ocean. Meltwater coming from these ice sheets drains into the ocean, ...