Is Dissolving, Boiling, Rusting a Chemical Or Physical Change?

Is Dissolving, Boiling, Rusting a Chemical Or Physical Change?

Is Dissolving, Boiling, Rusting a Chemical Or Physical Change? | Why Is Salt Dissolving a Chemical Change?


The appearance or form of matter changes during a physical change, but the type of matter in the substance does not. On the other hand, a chemical change results in the formation of at least one new substance with new properties.

It’s difficult to tell the difference between physical and chemical change. Students are frequently persuaded to assume that a change is physical or chemical. In reality, this should be viewed as a progression.

Salt dissolving in water, for example, is typically thought of as a physical change. Yet, the chemical species in salt solution (hydrated sodium and chlorine ions) differ from those in solid salt. Even if it is possible to recover the original components physically, dissolving instant coffee in water appears to be a physical change.

However, in most circumstances, dissolving is accompanied by an energy change and is probably better considered a chemical process. Many examples of materials dissolving (such as Alka Seltzer in water, metal in acid, and acid rain’s effect on marble and concrete) involve chemical and physical processes. 

Is it a chemical or a physical change when you dissolve table salt (sodium chloride, often known as NaCl) in water? On the other hand, a chemical change entails a chemical reaction, with new compounds emerging due to the change. On the other hand, a physical change causes the material’s appearance to change, but no new chemical compounds are produced.

Why Is Salt Dissolving a Chemical Change?

When you dissolve sodium chloride in water, it separates into Na+ and Cl- ions, which may be represented as a chemical equation:

NaCl(s) → Na+(aq) + Cl-(aq)

As a result, dissolving salt in water is a chemical transformation. The reactant (sodium chloride, or NaCl) and the products are different (sodium cation and chloride anion).

Any ionic compound that is soluble in water would undergo a chemical transformation. Dissolving a covalent substance like sugar, on the other hand, does not result in a chemical reaction. As it is dissolved, the sugar molecules distribute throughout the water, but they do not change their chemical identity. 

Why Do Some People See Salt Dissolving as a Physical Change?

Look up the solution to this question on the internet. You’ll find approximately an equal amount of people contending that dissolving salt is a physical rather than a chemical change.

The misunderstanding stems from a typical test for distinguishing chemical from material changes: if the starting substance in the transformation can be restored using just physical processes. Salt can be obtained by boiling the water from a salt solution.


Boiling is a physical transformation. New chemicals occur in chemical reactions (reactions), but no new substances appear in biological processes like boiling. The sense that is both liquid and gas is the same (water H2O).

Boiling is the fast evaporation of a liquid when heated to its boiling point. The temperature at which the liquid’s vapor pressure equals the surrounding atmosphere’s pressure.

Nucleate boiling, in which tiny vapor bubbles develop at distinct places, and critical heat flux boiling, in which the boiling surface is heated above a critical temperature and a film of vapor forms on the surface, are the two basic types of boiling.

Transition boiling is a shaky, intermediate form of boiling that contains elements from both states. The boiling point of water is 100 degrees Celsius (212 degrees Fahrenheit). However, it is lower at higher elevations due to lower air pressure.

Water is made potable by boiling it, which kills any germs or viruses that may be present. The sensitivity of different microorganisms to heat varies, although most microorganisms and viruses are inactivated after one minute at 100 °C (212 °F). In ten minutes, most germs can be killed at 70 degrees Celsius (158 degrees Fahrenheit).

Boiling water is also utilized in various cooking techniques such as poaching, steaming, and burning.

Types \s Nucleate

The formation of bubbles or pops on a heated surface, which rises from discrete places on a character whose temperature is only slightly above the temperature of the liquid, is known as nucleate boiling. A rise in surface temperature increases the number of nucleation sites in general.

An uneven boiling vessel surface (i.e., increased surface roughness) or fluid additives (i.e., surfactants and nanoparticles) allow nucleate boiling over a more comprehensive temperature range. In contrast, an excessively smooth surface, such as plastic, allows superheating. A heated liquid may demonstrate boiling delay under certain conditions, and the temperature may rise slightly above the boiling point without boiling.

Heat flux at a critical level

The thermal limit of a situation where a phase transition occurs during heating (such as bubbles forming on a metal surface used to heat water), which causes an abrupt decrease in heat transfer efficiency, causing localized overheating of the heating surface, is known as critical heat flux (CHF).

A coating of vapor forms on the boiling surface as it is heated over a critical temperature. The temperature rises very quickly beyond this point into the transition boiling regime because this vapor sheet is far less capable of transporting heat away from the surface. The point at which this happens is determined by the boiling fluid’s properties and the heating surface in the issue.


Transition boiling is the unstable boiling between the maximum achievable nucleate and the minimum likely in film boiling at surface temperatures in between.

The creation of bubbles in a heated liquid is a complicated physical process that frequently involves cavitation and acoustic effects, such as the broad-spectrum heard in a kettle that isn’t quite hot enough for bubbles to boil to the surface.


When a surface heating a liquid is much hotter than the liquid, film boiling occurs, in which a thin layer of vapor insulates the surface with low thermal conductivity. Film boiling is defined as forming a vapor film that isolates the character from the liquid.


Rusting of iron is a chemical alteration caused by forming a new material called iron oxide. Rusting requires the presence of oxygen as well as water or water vapor.

Chemical transformations

Chemical Alterations Chemical modifications result in the formation of new compounds. The properties of the newly produced substances are vastly different from the qualities of the original meanings. Rusting of iron, burning magnesium ribbon, converting the color of blue copper sulfate solution to green after leaving an iron nail in it for some time, and mixing vinegar acid and baking soda are only a few chemical changes.

These are long-term changes that cannot be reversed. In this type of transformation, much energy is either absorbed or released. This alteration may result in the production of sound. This modification could result in the production of gas. This alteration will result in a change in smell or a new smell.

Iron Corrosion When an iron object is exposed to wet air for an extended period, it develops a rusty reddish-brown flaky substance. This is referred to as iron rusting.

The rusting process is depicted as follows:

Iron(Fe) + Oxygen( ) + O2 Water(H2O) → Rust(iron oxide Fe2O3)

Rusting of iron is a chemical alteration caused by forming a new material called iron oxide. Rusting requires the presence of oxygen as well as water or water vapor. Rusting is a constant process that eats away at iron items, rendering them worthless. Painting, using grease or oil, galvanization, and chromium coating can all help to keep iron from rusting. Galvanization is the technique of coating iron things with a thin layer of zinc metal to prevent rusting.