Properties of Matter in Chemistry | Physical, Chemical

All properties of matter are either extensive or intensive and either physical or chemical.

matter in chemistry
  • Extensive properties, such as mass and volume, depend on the amount of matter that is being measured.
  • Intensive properties, such as density and color, do not depend on the amount of matter.

Both extensive and intensive properties are physical properties, which means they can be measured without changing the substance’s chemical identity.

Example

The freezing point of a substance is a physical property: when water freezes, it’s still water (H2O)—it’s just in a different physical state.

  • Meanwhile, the chemical property is any of a material’s properties that becomes evident during a chemical reaction; that is, any quality can be established only by changing a substance’s chemical identity. Chemical properties cannot be determined just by viewing or touching the substance; its internal structure must be affected for its chemical properties to be investigated.

The different types of matter can be distinguished through two components: composition and properties. The composition of matter refers to the different components of matter along with their relative proportions. Properties of matter refer to the qualities/attributes that distinguish one sample of matter from another. These properties are generally grouped into two categories: physical or chemical.

  • Physical properties are characteristics that scientists can measure without changing the composition of the sample under study, such as mass, color, and volume (the amount of space occupied by a sample).
  • Chemical properties describe the characteristic ability of a substance to react to form new substances; they include its flammability and susceptibility to corrosion.
  • All samples of a pure substance have the same chemical and physical properties.

For example, pure copper is always a reddish-brown solid (a physical property) and always dissolves in dilute nitric acid to produce a blue solution and a brown gas (a chemical property).

Properties of matter

Physical Properties can be Extensive or Intensive

  • Extensive properties vary with the amount of the substance and include mass, weight, and volume.
  • Intensive properties, in contrast, do not depend on the amount of the substance; they include color, melting point, boiling point, electrical conductivity, and physical state at a given temperature.

For example, elemental sulfur is a yellow crystalline solid that does not conduct electricity and has a melting point of 115.2°C, no matter what amount is examined.

Scientists commonly measure intensive properties to determine a substance’s identity, whereas extensive properties convey information about the amount in a sample.

Although mass and volume are extensive properties, their ratio is an important intensive property called density ( ρ ).

Density is defined as mass per unit volume and is usually expressed in grams per cubic centimetre (g/cm3). As mass increases in a given volume, density also increases.

For example, lead, with its greater mass, has a far greater density than the same volume of air, just as a brick has a greater density than the same volume of Styrofoam. Pure water, for example, has a density of 0.998 g/cm3 at 25°C.

Notice that corn oil has a lower mass to volume ratio than water. This means that when added to water, corn oil will “float”.

Physical Properties of Matter

A physical property is a characteristic of matter that is not associated with a change in its chemical composition.

Familiar examples of physical properties include density, colour, hardness, melting and boiling points, and electrical conductivity. We can observe some physical properties, such as density and colour, without changing the physical state of the matter observed.

Other physical properties, such as the melting temperature of iron or the freezing temperature of the water, can only be observed as matter undergoes a physical change.

Examples of physical properties are colour, smell, freezing point, boiling point, melting point, infra-red spectrum, attraction (paramagnetic) or repulsion (diamagnetic) to magnets, opacity, viscosity and density.

There are many more examples. Note that measuring each of these properties will not alter the basic nature of the substance.

Physical Change

A physical change is a change in the state or properties of matter without any accompanying change in its chemical composition (the identities of the substances contained in the matter).

Examples

We observe a physical change when, for example, wax melts, sugar dissolves in coffee, and steam condenses into liquid water.

Other examples of physical changes include magnetizing and demagnetizing metals (as is done with common anti-theft security tags) and grinding solids into powders.

In each of these examples, there is a change in the substance’s physical state, form, or properties but no change in its chemical composition.

Physical changes are changes in which no chemical bonds are broken or formed. This means that the same types of compounds or elements at the beginning of the change are there at the end of the change.

Because the ending materials are the same as the beginning materials, the properties (such as colour, boiling point, etc.) will also be the same.

Physical changes involve moving molecules around, but not changing them.

Some types of physical changes include
  • Changes of state (changes from a solid to a liquid or a gas and vice versa).
  • Separation of a mixture.
  • Physical deformation (cutting, denting, stretching).
  • Making solutions (special kinds of mixtures).

As an ice cube melts, its shape changes as it acquires the ability to flow. However, its composition does not change.

Melting is an example of a physical change since some properties of the material change, but the identity of the matter does not. Physical changes can further be classified as reversible or irreversible.

The melted ice cube may be refrozen, so melting is a reversible physical change. Physical changes that involve a change of state are all reversible.

Other changes of the state include vaporization (liquid to gas), freezing (liquid to solid), and condensation (gas to liquid). Dissolving is also a reversible physical change.

When salt is dissolved into water, the salt is said to have entered the aqueous state. The salt may be regained by boiling off the water, leaving the salt behind.

Chemical Properties of Matter

The change of one type of matter into another type (or the inability to change) is a chemical property.

Examples-: Chemical properties include flammability, toxicity, acidity, reactivity (many types), and heat of combustion.

Iron, for example, combines with oxygen in the presence of water to form rust; chromium does not oxidize. Nitroglycerin is very dangerous because it explodes easily; neon poses almost no hazard because it is very unreactive.

Chemical Change

Chemical changes occur when bonds are broken and/or formed between molecules or atoms. This means that one substance with a certain set of properties (such as melting point, color, taste, etc) is turned into a different substance with different properties.

Chemical changes are frequently harder to reverse than physical changes.

How to Identify a Chemical Change

To identify a chemical property, we look for a chemical change. A chemical change always produces one or more types of matter that differ from the matter present before the change.

The formation of rust is a chemical change because rust is a different kind of matter than the iron, oxygen, and water present before the rust formed.

The explosion of nitroglycerin is a chemical change because the gases produced are very different kinds of matter from the original substance.

Other examples of chemical changes include reactions performed in a lab (such as copper reacting with nitric acid), all forms of combustion (burning), the ripening of fruits, and food being cooked, digested, or rotting.

Examples

  • One good example of a chemical change is burning paper. In contrast to ripping paper, burning paper results in new chemicals (carbon dioxide and water, to be exact). Another example of chemical change occurs when water is formed. Each molecule contains two atoms of hydrogen and one atom of oxygen chemically bonded.
  • Another example of a chemical change occurs when natural gas is burned in your furnace. This time, before the reaction, we have a molecule of methane, CH4, and two molecules of oxygen, O2, while after the reaction, we have two molecules of water, H2O, and one molecule of carbon dioxide, CO2. In this case, not only has the appearance changed, but the structure of the molecules has also changed. The new substances do not have the same chemical properties as the original ones. Therefore, this is a chemical change.

The combustion of magnesium metal is also chemical change (Magnesium + Oxygen → Magnesium Oxide):
2Mg + O2 → 2MgO
as is the rusting of iron (Iron + Oxygen → Iron Oxide/ Rust):
4Fe + 3O2 → 2Fe2O3
Using the components of composition and properties, we have the ability to distinguish one sample of matter from other.

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