The Law of conservation of matter states that matter cannot be created or destroyed; only its form can change. It can undergo either a physical and chemical changes. Composition distinguishes a physical reaction from a chemical reaction. Matter’s properties, such as state of matter, shape, and chemical properties such as a chemical formula, can endure a variety of transformations. The transformation can be categorized as physical and chemical changes. The distinction between physical and chemical changes resides in the nature of the affected properties.
Physical Change
Physical change is a process that involves changing a material’s physical characteristics, such as shape, size, volume, appearance, color, and state (such as solid, liquid, or gas), etc., without changing its chemical composition. These changes are unstable, and they can be undone with basic physical techniques.
Types of Physical changes
State changes: When water is frozen, it changes shape and form to become solid, but the molecules remain the same. Similarly, it can be liquified and evaporated, changing its state from liquid to gas. These changes in the state don’t result in any molecular changes.
Changes in the state include evaporation (liquid to gas), freezing (liquid to solid), and evaporation (gas to liquid). Melting (from solid to liquid) is also a reversible physical change.
Deformation of Shape: When matter changes its shape it does not necessarily change its molecular compositions. For example, crushing the soda can change its shape but its chemical composition remains the same. Another example can be folding of money.
Change in Temperature: When the temperature changes, some physical changes can occur. For example, when an iron rod is heated, it glows red, while its chemical composition does not change.
Making a solution: When salt is dissolved in water, it does not change the materials chemically. It still has salt and water. When we separate the mixture by distillation or the simple evaporation of the water. The salt would be the residue, and the water would be the distillate.
Changing the color: The change of color in a substance is not necessarily an indicator of a chemical change. For example, metal does not change its physical properties when painted. Painting the metal car does not change the composition of the metallic substance.
Physical Properties
Ductility: It is one of the most important physical properties of metal. Ductility allows the material to be pulled into a thin thread of wire without breaking it. For example, copper can be drawn into a thin wire, allowing it to be used inside the electric cable without changing its chemical properties.
Malleability: When metal is malleable, it can be hammered into a thin sheet without changing its chemical composition. For example, gold and silver can be beaten into thin sheets, allowing them to be used as jewelry.
Density: The density of an object is its mass divided by its volume (d=m/v). An object’s density will determine whether it will sink or float in a particular chemical. For example, it has a liquid density of 1 g/cm3. Any substance with a density lower than that will float in water. For example, metals are used to build ships with the help of this property.
Chemical Change
A chemical change occurs when chemicals transform into new compounds with different properties. It happens when a chemical reacts with another to make a new compound (synthesis) or breaks down to produce additional chemicals. The oxidation reaction is a chemical change that causes a chemical reaction.
They are irreversible unless other chemical processes are carried out.
Characteristics Of Chemical Changes
Change in color: A chemical reaction can change the color of a substance. It is one of the chemical changes taking place. For example, when metal is oxidized, it can rust and change its color to bright orange. This change of color is evidence of a chemical reaction.
Distinctive Odor/Smell: An element may not have any smell on its own, but when two or more substances are brought together, a chemical reaction occurs. This reaction can release an odor. This kind of odor is an indication of a chemical reaction. For example, when food is rotten, it develops an odor.
Change In Temperature: During the chemical reaction, a temperature change is observed. The temperature can get hotter or colder, depending on the type of reaction. If the reaction releases heat, it is known as an exothermic reaction, whereas reactions that absorb heat are known as endothermic reactions.
Precipitate: The formation of a precipitate occurs commonly during chemical reactions. It can be defined as a solid formed inside a solution or another solid. For example, when soluble carbonate reacts with barium, barium carbonate precipitates.
Bubble Formation: During a chemical reaction, bubbles or gas can form. For example, when sodium carbonate (NA2CO3) reacts with enough hydrochloric acid (HCl), carbon dioxide (CO2) bubbles start to form.
Types Of Chemical Change
There are three main type of chemical change that include:
Chemical changes in Organic Compounds: Organic substances are made up of carbon atoms that are covalently linked to atoms of other elements. Chemical reactions involving an organic molecule include ripe fruit, the burning of natural gases, rotten eggs, etc.
Chemical changes in Inorganic Compounds: It does not involve carbon. This type of chemical change usually occurs in laboratories. These types of changes include neutralization, oxidization, redox reactions, etc.
Biochemical Changes: Biochemistry deals with the chemistry of the growth and activity of living organisms. It is a type of chemistry where hormones moderate and restrict most reactions while complex proteins known as enzymes control them. This is always highly complex and is still not fully understood. Photosynthesis is one of the example involving biochemical change.
Difference Between Physical and Chemical Changes
| Physicals Changes | Chemical Changes |
| Physical changes involve a change in the substance’s shape or appearance but not its composition. | A chemical change alters the nature of the matter and results in the formation of at least one new substance with distinctive characteristics. |
| It is temporary change | It is permanent change |
| Typically, physical transformations do not result in the production of energy. | Chemical reactions involve the release of energy (in the form of heat, light, sound, etc.). |
| Physical transformations are readily reversible, meaning the original substance can be recovered. | Chemical changes are permanent, which means that the original substance cannot be turned back. |
| Mechanical forces, such as grinding, polishing, etc., are capable of causing physical changes. | Mechanical forces are difficult to induce chemical changes. |
| Applications of physical changes include the separation of compounds through distillation, the production of granules from substances, and the alteration of the texture or shape of materials, among others. | The applications of chemical change include the synthesis of novel chemical molecules with specific properties, the production of energy through methane plants, etc. |
| Physical change alter the physical properties like size, and shape and does not involve the release of light, sound, heat, etc. | A chemical change can produce energy in the form of light, heat, sound, etc. |
| Examples of physical change: freezing of water into ice, ball-milling, grinding, sublimation of camphor, boiling of water. | Examples of chemical change: Burning of coal, formation of milk into curd, rusting of iron, digestion of food, etc. |
How do you know if CHEMISTRY is happening? What changes let you know a Chemical Reaction has happened, vs just a Physical change?
References
- https://education.nationalgeographic.org/resource/changes-matter-physical-vs-chemical-changes/
- Atkins, P.W.; Overton, T.; Rourke, J.; Weller, M.; Armstrong, F. (2006). Shriver and Atkins Inorganic Chemistry (4th ed.). Oxford University Press. ISBN 0-19-926463-5.
- Chang, Raymond (1998). Chemistry (6th ed.). Boston: James M. Smith. ISBN 0-07-115221-0.
- https://www.studysmarter.co.uk/explanations/chemistry/chemical-reactions/physical-and-chemical-changes/
- Clayden, Jonathan; Greeves, Nick; Warren, Stuart; Wothers, Peter (2001). Organic Chemistry (1st ed.). Oxford University Press. ISBN 978-0-19-850346-0.
- https://www.bbc.co.uk/bitesize/guides/zw6jh39/revision/3
- Kean, Sam (2010). The Disappearing Spoon – And Other True Tales From the Periodic Table. Black Swan, London. ISBN 978-0-552-77750-6.
- Zumdahl, Steven S. and Zumdahl, Susan A. (2000). Chemistry (5th Ed.). Houghton Mifflin. ISBN 0-395-98583-8.
- https://leverageedu.com/blog/physical-and-chemical-changes/
- https://www.thoughtco.com/physical-and-chemical-changes-examples-608338
- https://www.education.vic.gov.au/school/teachers/teachingresources/discipline/science/continuum/Pages/physchem5.aspx#:~:text=In%20a%20physical%20change%20the,with%20new%20properties%20is%20formed.
