What is a physical example? Describe a physical change, such as the transformation of a solid to liquid or from a solid to a liquid. The appearance of matter changes, but the underlying chemical identity is preserved. For example, solid sulfur changes color when it changes from a solid to liquid form. In contrast, the color of several nonmetals changes as they change phases. Nonmetals that change color are radon and oxygen. Chemical reactions cause physical changes as well, like color and temperature.
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Heat
A physical example of heat is a process by which a body passes on energy. Heat is a measurable quantity that is capable of converting into mechanical work. After the abandonment of the caloric theory and the development of thermometry, the quantity of heat was defined. Now, the concept of heat can be interpreted in terms of gas kinetics. But before discussing heat, it is necessary to know what it is.
A physical example of heat is energy transfer associated with a disordered microscopic action on a system. This disordered action causes jumps in the occupation of energy levels. Although macroscopic thermodynamic work also changes the occupation of energy levels, only disordered microscopic action contributes to heat. This also includes radiative transfer. The term heat is often misleadingly called ‘heat content’ or ‘heat function’, but in fact, it is a measure of the energy transferred via covalent and intermolecular bonds in a system.
A physical example of heat is radiation, which is the transfer of energy through electromagnetic waves. The energy is released from an object that is warm, and it absorbs this energy to give off energy. The heat from the sun is absorbed by atoms in objects, and a change in temperature will cause corresponding changes in the energy inside an object. This change in energy will also result in a change in state. The type of material can play a major role in determining how much energy an object can store.
When two objects are heated, molecules inside each object will attempt to reach the same temperature as the other. This is called thermal equilibrium. When temperatures are the same, the molecules in both objects are equal in temperature. Once this equilibrium is achieved, the temperatures will remain stable. Whether it is water, air, or a solid will eventually be at the same temperature. And the process will repeat again. The process of heating objects is explained by the theory of thermodynamic equilibrium.
Temperature
Thermodynamics describes temperatures and other properties of matter by the use of a microscopic description based on the classical degree of freedom (DOF) of particles. Theoretical calculations based on the DOF yield a more rigorous description of thermal motion. Thermal motion is also described using the kinetic theory of gases, which relates the macroscopic description to the probability distribution of the energy of motion of gas particles.
The average kinetic energy of particles within an object is the temperature. This means that the more quickly the particles are moving, the higher the temperature. The opposite is true, and slower-moving particles will feel cooler than those that are moving faster. By comparison, heat is the flow of energy from one body to another. For this reason, temperature is used in physics to describe the flow of energy. This way, we can see how heat is converted into different temperature values.
The temperature scales used in science and engineering are the Fahrenheit, Celsius, and Kelvin units. Both scales measure temperature, and historically were calibrated using a thermometric substance. The Kelvin scale, formerly degF, is now primarily used for scientific purposes. The Fahrenheit and Celsius scales are equivalent and use the same mathematical formulae, but the Kelvin scale is more precise. Temperature is another important physical example in medicine, ecology, and material science.
The temperature scales can be measured in either Celsius, Kelvin, or Fahrenheit, and each has its own correlation. Vedantu offers a full explanation of temperature, along with examples and a relation between kinetic energy and temperature. It also offers 3-D illustrations of the concepts taught in physics courses. In addition, the Vedantu website is a great resource for learning about thermodynamics.
Reversible or irreversible changes
There are two types of physical changes: reversible changes and irreversible ones. An irreversible change occurs when a reactant changes into a new material, and cannot be changed back. Examples of irreversible changes include boiling, burning, and mixing. Burning an object will produce smoke and ash. After it cools, it cannot be turned back into paper. Another example of irreversible changes is the melting and dissolving of a substance.
Reversible changes involve the formation of new substances. For example, a solid substance can turn into a liquid by reacting with water vapour. The water molecules in the liquid turn slower as the temperature decreases. However, the water molecules do not change completely once they have become solid. Similarly, a liquid can change back into a solid after freezing, and vice versa. In some cases, the process of freezing can be reversed and the material can be turned back into liquid again.
Another reversible change involves a material that has been changed physically. For example, a wet lump of clay can be shaped into a pot. This change is reversible. The wet lump of clay can be returned to its original form after the process is complete. In contrast, baking a pot makes the clay harden and make it more durable. The final step, however, is irreversible and requires a higher temperature and pressure than the initial condition.
A chemical example of an irreversible change is rusting. The metal can be reconstituted, but the copper lion statue has become oxidized. Both physical and chemical changes in a material have their uses. Some of these changes are essential to our society, but others are not. They can also make a difference to a particular species. One example of an irreversible change is the dissolution of potassium chromate.
Chemical reactions
Often, students use the term ‘chemical change’ to describe the change of a substance. They might refer to boiling or freezing as examples. Nevertheless, they should consider that a change in colour or temperature does not necessarily indicate a chemical change. Another example of a physical change is the dissolution of potassium permanganate (Condy’s crystals) in water. Students who do not understand chemical change should consider the following examples to gain a better understanding of the concept.
First, you should know the concept of stoichiometry. Stoichiometry is the ratio of reactants to products in a chemical reaction. This relationship is essential because chemical processes require conservation of matter. Mole is a unit of mass. One mole of carbon-12, for example, contains 12 grams of carbon. The same rule applies to any other compound. Hence, the more reactants, the more energy the reaction will produce.
Another physical example of chemical reactions is baking a cake. In baking a cake, a wet dough turns into an amazing dessert. Changing chemical composition involves breaking or forming chemical bonds. The result is a completely new substance with different properties. Unlike the physical example, the chemical change is irreversible. Chemists look at several basic indicators to determine whether a substance is changing. These indicators include change in color, temperature, and odor. It may also produce a precipitate or gas.
Another physical example of chemical reactions is a change in the shape of a compound. A melted or boiled glass is still water; the same goes for boiling or melting water. A nail that has come into contact with water undergoes rusting. This process also involves a change in the shape and chemical composition of a metal. In contrast, a melted or boiled piece of metal is transformed into a new substance.
Material dissolving
Physical examples of material dissolving include the breakdown of an alka-seltzer solution or the melting of metal. Acid rain can also dissolve concrete and marble. The processes involved in dissolving materials involve both physical and chemical reactions. To understand how a dissolving process occurs, consider two examples of materials that have similar molecular structures. In each example, the solute and the solvent exhibit opposite attractive forces.
Solubility is an important property of a substance and can affect its rate of dissolving. In general, the higher the solubility, the faster the solid dissolves. Moreover, the size of the grain and the temperature of the mixture determine the speed at which a solid dissolves. For instance, a teaspoon of vinegar can dissolve an eggshell’s calcium carbonate. The dissolving rate depends on the two substances’ physical properties and the nature of the solvent.
In addition to water, virtually any liquid or gas can act as a solvent. In fact, many alloys are solid solutions of metals. In a US five-cent coin, nickel is dissolved in copper. Other materials – such as alcohol and sugar – dissolve in water. In the table below, different materials can be dissolving in water. The same applies to a solid solution. A colloidal solution is made of particles smaller than those of a true solution.
Another physical example of material dissolving is the burning of steel wool in air. The result is a black powder. The chemical reaction takes place when the reactant and the product increase in weight. The same principle applies in an electrochemical reaction. The chemical reactions that power rechargeable electronic devices are used for charging batteries, and determining how a chemical reaction changes the electrochemical current in them might be beneficial for a future research project.
