Physical properties are characteristics of a substance that can be observed or measured without altering its chemical composition. These attributes describe the state and behavior of matter. When a physical property is examined, the substance remains chemically the same, allowing for the identification and categorization of materials.
Common Physical Properties
The state of matter refers to whether a substance exists as a solid, liquid, or gas. A solid, like ice, maintains a fixed shape and volume. A liquid, such as water, has a definite volume but takes the shape of its container. A gas, like water vapor, expands to fill its container and has no fixed shape or volume.
Density quantifies how much mass is contained within a given volume of a substance. It is calculated by dividing an object’s mass by its volume, often expressed in units like grams per cubic centimeter (g/cm³). For instance, a block of wood floats on water because wood is less dense than water, while a rock sinks because it is denser.
Melting point and boiling point are specific temperatures at which a substance changes its state. The melting point is the temperature at which a solid transforms into a liquid, such as ice melting into water at 0 degrees Celsius. The boiling point is the temperature at which a liquid turns into a gas, like water boiling at 100 degrees Celsius at standard atmospheric pressure.
Other easily observable physical properties include color, odor, and texture. Examples include the reddish-brown color of copper, the pungent smell of ammonia, or the smooth feel of polished glass. These properties aid in the initial identification of materials.
Solubility describes the maximum amount of a substance that can dissolve in a specific amount of solvent at a given temperature to form a solution. For example, sugar is highly soluble in water, while sand is largely insoluble.
Hardness measures a material’s resistance to permanent deformation, such as scratching or indentation. Diamonds are known as the hardest natural substance, capable of scratching almost any other material. Talc, on the other hand, is a very soft mineral that can be easily scratched with a fingernail.
The ability of a substance to transfer heat or electricity is described by its conductivity. Metals like copper are excellent electrical conductors, which is why they are used in wiring. Similarly, materials such as silver exhibit high thermal conductivity, making them suitable for applications where rapid heat transfer is desired.
Physical Versus Chemical Properties
The distinction between physical and chemical properties lies in whether the observation or measurement process alters the substance’s chemical identity. When a physical property is observed, the substance does not change into a new substance. For example, when water freezes into ice, it is still water (H₂O), just in a different physical state.
In contrast, chemical properties describe a substance’s potential to undergo a chemical change, resulting in the formation of entirely new substances. These properties are observed during or after a chemical reaction. An example is flammability, the ability of a substance to burn in the presence of oxygen. When wood burns, it transforms into ash, smoke, and gases, which are chemically different from the original wood.
Another chemical property is reactivity with acid. When baking soda reacts with vinegar, carbon dioxide gas is produced, indicating a chemical change. Oxidation, such as rusting in iron, is also a chemical property, as iron combines with oxygen to form iron oxide, a new compound with different characteristics.