What Are Physical Properties? Key Concepts and Examples
Anything that occupies space and has some mass is called matter. And every matter in this universe consists of physical and chemical properties which change when it undergoes reaction. These properties of matter are either chemical or physical and further, these physical properties are either extensive or intensive. It is important to study the properties of substances to understand their nature. Every substance reacts differently as all of them consist of different physical properties. There are different ways to observe the physical and chemical properties of the substances. For example, non metals have different ways of reacting towards acid from metals as the properties of metals and non-metals differ.
Properties of Substances
These properties are either intensive or extensive or they can be classified as physical or chemical. The examples of extensive properties are volume or mass depending on the amount of the measured matter. The examples of intensive properties are color or density which do not depend on the amount of matter. It is important to note that physical properties are both intensive or extensive properties. These can be estimated without controlling the chemical identity of the substances. The example of physical property can be explained with the help of freezing water, when we freeze the water, it will still remain water , however, only the physical state will change. The other examples of physical properties can be measured or demonstrated by studying color, density, volume and mass of the substances. It only changes the physical state of the substance but doesn't change the chemical composition of the substances. Some changes also include more than one type of change in their properties. For example, if we blend two fruits to make a juice. This change will include two types of physical changes as it will change the state of matter from solid to liquid and mixing of pieces of fruits. However, there is no chemical change involved here. Some of the other physical change includes:
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Physical and Chemical Properties
As we discussed, the physical properties are the properties which are either intensive or extensive. The intensive properties are not seen with the naked eyes while the extensive ones are easily observed. The intensive ones are color, density while the extensive properties are the volume , mass etc. The reaction involving any change in these extensive or intensive properties is called physical properties. These changes did not result in any change of the chemical composition unlike the chemical change. For example, the physical properties of soil changes include the texture, porosity, density etc. It gets affected in case of soil erosion.
Similarly, the physical properties of acid which are most likely to change when it undergoes any reaction are its sour taste, the change in its color (litmus paper).
The chemical properties are referred to as that property which lead to the change in the chemical structure. The examples of chemical properties are the heat of combustion which is the energy released when a compound undergoes complete combustion (burning) with oxygen, or Chemical stability which is determined if a compound will react with water or air as the stable chemical substance will not react. The chemical changes are the changes which lead to change in the chemical composition example, cooking, rusting etc. as they produce new chemical compounds.
Physical Properties of Non Metal
There is a significant difference between metal or non-metals. The appearance of metals and non metals differs due to their different physical properties. The intensive or extensive physical properties of the nonmetal determine its appearance and its reaction with other substances. These physical properties can be of great utility in some cases. For example, copper is used to make electrical wires as they are conductors and will allow the electricity to pass. However, you cannot use non-metal in this case as it will not allow the electricity to pass. The physical properties of non-metal also decides its utility like high-ionization energies, poor conductor of heat, low density, etc.
Conclusion
The physical properties can determine its application. The physical properties are extensive or intensive. The extensive ones volume, mass etc and the intensive ones are the density, etc. The change which leads to the change in the physical property without affecting the chemical property is called Physical change. The change which results in the change of the chemical composition or it leads to the formation of a new chemical compound is called chemical change.
FAQs on Physical Properties in Chemistry
1. What is a physical property in chemistry?
A physical property is a characteristic of a substance that can be observed or measured without changing the substance's chemical identity. These properties describe the appearance, feel, or behaviour of a substance. For example, you can observe the colour of a compound or measure its boiling point without altering its chemical formula.
2. What are some common examples of physical properties?
Common examples of physical properties used to describe matter include:
Colour: The visual appearance of a substance.
Density: The mass of a substance per unit volume (D = m/V).
Melting Point: The temperature at which a solid turns into a liquid.
Boiling Point: The temperature at which a liquid turns into a gas.
Malleability: The ability to be hammered into thin sheets.
Ductility: The ability to be drawn into wires.
Solubility: The ability of a substance to dissolve in a solvent.
Electrical Conductivity: The ability to conduct an electric current.
3. How do physical and chemical properties differ?
The key difference lies in whether the substance's chemical composition changes during observation. Physical properties, like melting point or density, can be measured without altering the substance's identity. In contrast, chemical properties describe how a substance reacts or changes to form a new substance. Examples of chemical properties include flammability (how easily it burns), toxicity (how poisonous it is), and reactivity with acids.
4. What is the difference between intensive and extensive physical properties?
This distinction is based on whether the property depends on the amount of matter present.
An intensive property is independent of the amount of the substance. Examples include temperature, density, and boiling point. A drop of water and a swimming pool of water will have the same boiling point (100°C at standard pressure).
An extensive property depends on the amount of the substance. Examples include mass, volume, and length. A swimming pool has a much greater mass and volume than a single drop of water.
5. How can physical properties be used to identify an unknown substance?
Physical properties act like a substance's fingerprint. By measuring several intensive properties, which do not change with the sample size, a scientist can identify an unknown material. For instance, if you measure a substance's density to be 7.87 g/cm³, its melting point to be 1,538°C, and observe that it is magnetic, you can confidently identify it as iron. No other substance will have this unique combination of properties.
6. Why is boiling water to make steam considered a physical change related to a physical property?
Boiling is related to the physical property called boiling point. It is considered a physical change, not a chemical one, because the chemical identity of the water does not change. The water molecules (H₂O) are the same in liquid form and in steam (gaseous form). The change is only in the state of matter and the distance between the molecules, not in the chemical bonds within the molecules themselves. The process is reversible by cooling the steam.
7. How do intermolecular forces influence physical properties like melting and boiling points?
Intermolecular forces are the attractions between neighbouring molecules. These forces have a direct impact on physical properties:
Stronger intermolecular forces (like hydrogen bonding in water) require more energy to pull the molecules apart. This results in a higher melting point and boiling point.
Weaker intermolecular forces (like London dispersion forces in methane, CH₄) require less energy to overcome. This leads to a lower melting and boiling point, which is why methane is a gas at room temperature.
