Pure Substance

Pure Substances in Chemistry are those which consist of only one type of atom or in the case of more than one type of atom they are always combined in a fixed ratio. What we consider as Pure is not a Pure Substance as per the definitions of chemistry. For Example, we consider milk as pure when it has no adulteration however as per definitions of chemistry Milk is not a Pure Substance.

All the matter around us is classified as Pure Substance and Mixture. Pure Substance forms the basis of all the important chemical compounds. In this article, we will learn about the Pure Substance in detail, learning about the properties and types of pure substance and its comparison with mixture.

What is Pure Substance?

Pure substance as we know “Pure” means something that consists of only one type of particle and has a fixed or constant structure. Also, they have properties that can be predicted, that is why they are useful for studying some properties such as melting point, boiling point, density, solubility, and reactivity. These properties make pure substances the base of chemistry because their properties and interactions with other materials can be used for forming new types of matter.

Pure Substance Definition

Pure Substances are those that have constant chemical composition means the composition of pure substances will always be the same. A pure substance has both definite and constant composition and distinct chemical properties. To avoid confusion, a pure substance is also known as a “chemical substance”.

Pure Substance Example

Gold, iron, oxygen, Water, salt, sugar, carbon dioxide are examples of Pure Substance.

Types of Pure Substances

Pure substance are further divided into two types on basis of chemical composition

• Elements
• Compounds

Elements are such kind of pure substances which contain atom of only one type and cannot be broken down into more substances while Compound are substances which are made up of more than one atom and can be separated by chemical methods

The details of Elements and Compounds are discussed below:

Characteristics and Properties of Pure Substance

A pure substance is a single form of matter that has specific chemical and physical properties, allowing it to be identified and utilized distinctly from mixtures. Such substances are pure because they consist entirely of one type of atom or molecule. This intrinsic purity gives them unchanging properties that do not fluctuate with environmental conditions, provided those conditions remain stable.

Consistency in Properties

The uniform composition of pure substances means their properties, such as boiling points, melting points, and density, are constant. For instance, pure water has a boiling point of 100°C at standard atmospheric pressure, and this does not change unless external conditions like pressure are altered.

Examples and Relevance

Elements like gold and silver, and compounds such as salt (sodium chloride) and sugar (sucrose), are classic examples of pure substances. These materials are fundamental in both everyday applications and high-precision scientific endeavors. In laboratories, the consistent behavior of pure substances makes them indispensable for experiments needing exact measurements and predictable results.

Utility in Research and Industry

The predictable properties of pure substances allow scientists and engineers to use them to create standards and calibrate equipment. Moreover, their purity is crucial for chemical reactions where the presence of impurities could lead to unwanted side effects or hazardous conditions.

What is a Mixture?

Mixtures are combinations of two or more substances where each substance retains its chemical identity and properties. They do not undergo chemical changes when combined; instead, they form physical blends that can usually be separated by mechanical means.

Types of Mixtures

There are primarily two types of mixtures

• Homogeneous Mixtures: These have a uniform composition throughout. Solutions like salt in water or the air we breathe are perfect examples. The individual components are so thoroughly mixed that they appear as one substance, though they can be separated into their original components through processes like distillation or evaporation.
• Heterogeneous Mixtures: These mixtures have a non-uniform composition and the different components can be visually distinguished. A classic example is a mixture of oil and water, or sand mixed with salt. These mixtures can often be separated simply by physical means like filtering or settling.

Prevalence and Importance

Mixtures are everywhere in daily life and industrial processes. Foods, medicines, and even personal care products are typically mixtures. Understanding how to manipulate these mixtures is crucial in fields such as pharmaceuticals, where the efficacy of a drug can depend on the way its various components are combined.

Phases of Pure Substance

The word “phase” refers simply to the state of matter of any pure substance: solid, liquid, or gaseous. Phases depend on temperature and pressure, in most cases. There are primarily three phases of pure substance

• Solid: The molecules of a solid are closely packed in a rigid structure. It has a definite form and volume.
• Liquid: Once the solid hits its melting point, it starts to turn into a liquid. At this stage, the solid does already have a certain volume but takes the form of the container; this level of freedom of molecules is much more than what is found in a solid.
• Gas: If the temperature gets higher than usual, then boiling sets in, and gas is formed. This occurs because gases have no definite shapes and volumes, so they tend to expand, filling up the volume of their container.

Phase Transitions

The transition of one state of matter to another—melting, freezing, vaporization, condensation, sublimation, and deposition is called Phase Transition. It is key to a number of industrial operations and nature cycling. The best example is the water cycle, which mostly depends upon the evaporation and condensation of water.

Application in Industries

Critical phase behavior control has an absolute necessity in an industrial setup during vital processes like distillation, for the separation of components on the basis of boiling points, or in cryogenics, where the study of a substance is made at very low temperature in its solid phase.

What are Elements?

An element is type of pure substance that consists only one type of atom in there composition and they cannot be broken down into simpler substances by physical or chemical methods. An element is the simplest form of matter that has unique properties. There are 118 known elements in the modern periodic table, which are further classified into metals, non-metals, and metalloids. Some examples of elements are gold, oxygen, carbon, iron, and helium .

Types of Elements

Elements can be divided into three types

• Metals
• Non Metals
• Metalloids

Metals

Metals are those elements which tend to lose electron from outermost shells to form cation. Metals have following properties

• Luster: Metals often have a shiny appearance due to their ability to reflect light.
• Conductivity: They are excellent conductors of both electricity and heat, making them essential in electrical wiring, electronics, and various applications.
• Malleability and Ductility: Metals can be hammered or rolled into thin sheets (malleability) and drawn into wires (ductility) without breaking.
• High Melting and Boiling Points: Metals typically have high melting and boiling points, which means they are usually solid at room temperature.
• Density: Most metals are dense materials, meaning they have a high mass per unit volume.

Non-Metals

Non metals are opposite of metals they tend to gain electron to form negative ions to gain stability

• Lack of Luster: A lot of non metals are gases, we know they don’t have specific color
• Poor Conductivity: They behave as insulators and cannot conduct electricity
• Brittle: Non-metals are often brittle and may shatter when subjected to mechanical stress.
• Low Melting and Boiling Points: Non-metals tend to have lower melting and boiling points, and many are gases or solids at room temperature.

Learn More, Metals and Non-Metals

Metalloids

Metalloids are like intermediate of metals and non metals because they have properties of both metals and non metals They are often used as semiconductors because they are not like metals which can conduct easily and also not like non metals which cannot conducts some some energy needed to be supplied in case of semiconductor in order to make them conduct electricity.

• Varied Conductivity: Metalloids can exhibit both metallic and non-metallic conductive properties.
• Semiconductor Behavior: Some metalloids, like silicon (Si), are widely used as semiconductors in the electronics industry.
• Mixed Physical States: Metalloids can exist in various states, such as solid, liquid, or gas, depending on conditions.

What are Compounds?

Compounds are pure substances which are made of atoms of more than single type or we can say that it consists of two or more elements which are chemically combined in a fixed ratio. Compounds have different properties from there constituent elements and also they can be broken down into simpler substances by certain chemical methods. For example, water is a compound that consists of two hydrogen atoms and one oxygen atom i.e. in a 2:1 ratio. Also, Water has different properties from elements from which its made.

Types of Compounds

Compounds can be of many types depending on the types of atoms used and the bonds formed among the atoms. A brief classification of compounds is given below:

• Organic Compounds
• Inorganic Compounds
• Ionic Compound
• Covalent Compounds
• Metallic Compound
• Coordination Compound

Organic Compounds

Organic Compounds are those in which the backbone of the structure is a hydrocarbon chain or carbon-carbon bond i.e. Organic Compounds mainly comprises of carbon and hydrogen as its parent atom and any other atoms as a substituent. Organic Compounds are basically found in living beings. Example include glucose (C₆H₁₂O₆), Methane(CH₄) etc. The first organic compound prepared in the lab was Urea (NH₂CONH₂)

Learn More, Classification of Organic Compounds

Inorganic Compounds

Inorganic compounds are those in which there is no carbon-carbon bond present. Inorganic Compound lacks the presence of hydrocarbon chain. They are mostly present in non living things. Examples include CO₂, CaCO₃, NH₃ etc.

Ionic Compounds

Ionic Compounds are formed by positively and negatively charged ions held together by a strong electrostatic force of attraction. They mostly have high melting and boiling points and are found as solids at room temperature. There common everyday examples are (sodium chloride, NaCl) and calcium carbonate (CaCO₃).

Covalent Compounds

Covalent compounds, are also known by molecular compounds, they form by sharing of electrons between atoms and not by complete transfer of electrons i.e. the shared electron revolve in the orbit of both the participating atoms. Unlike Ionic compounds they can exist in various states (solid, liquid, or gas) at room temperature, and they generally have lower melting and boiling points compared to ionic compounds. Common everyday examples are water (H₂O), carbon dioxide (CO₂), and methane (CH₄).

Metallic Compounds

Metallic compounds are composed of metal atoms arranged in a metallic lattice structure. They consist of metal properties like In these compounds, electrons are shared freely among the metal atoms, and these electrons give rise to high electrical and thermal conductivity. Common examples of metallic compounds include alloys like bronze (copper and tin) and steel (iron and carbon).

Coordination Compounds (Complexes)

Coordination compounds, or complexes, are formed by the coordination of metal ions with surrounding ligands. Ligands are molecules or ions that donate electron pairs to the central metal ion. Coordination compounds are often colorful and play a vital role in fields such as biochemistry and catalysis. Examples include hemoglobin (a complex of iron in the heme group and proteins) and the chlorophyll molecule (a complex containing magnesium).

Properties of Pure Substances

Lets see some basic properties of pure substances for understanding them better

• Definite Composition: Pure substances has a fixed composition, meaning it consists of a specific type and number of atoms or molecules. Like, pure water (H₂O) always contains two hydrogen atoms and one oxygen atom you can move any part of world pure water will be always H₂O.
• Fixed Melting and Boiling Points: Different Pure substances have different melting and boiling points at which they change from one phase to another. These temperatures remain constant and don’t change, means each pure substance have fixed melting and boiling point but the pressure must remain same This property allows for the separation and purification of pure substances through techniques like distillation.

• Homogeneity: Pure substances are homogeneous, which are substance which have a uniform composition throughout. So if we take any sample of pure substance, every part has the same properties as any other part.
• Chemical Reactivity: Pure substances have specific chemical properties that can be identified and measured which the chemical reactions possible. These properties tell us about how they interact with other substances, making them important for various chemical reactions.

Applications Pure Substances

Pure substances are very important as they are used in various fields such as chemistry, technology, medicines and as common substances in our everyday life. Lets see some uses of Pure substances

• Elements can be used to make alloys, jewellery, coins, magnets, batteries, catalysts, and many other products.
• We can make medicines, fertilizers, plastics, detergents, fuels, explosives, and many other products with help of compounds
• Pure substances are also used for scientific purposes, such as measuring physical constants, conducting experiments, and testing theories.
• Pure substances are also essential for life of human beings, animals, and plants. Life is possible because of existence of Pure Substances For example, water is a pure substance that is vital for life processes, such as hydration, digestion, respiration, and excretion

Pure Substance and Mixture

We have understand that pure substance is not combination of many atoms and is made up of one kind of element of element or compound while mixture is combination of different substance which are not chemically linked.

Pure Substance and Mixture Example

• Example of Pure Substance include elements like gold, aluminium and compound like water, carbon dioxide are pure substances.
• Example of Mixtures include the substance in which the composition can vary like air, milk, oil and water, etc. are mixtures.

Difference between Pure substance and Mixture

The key differences between pure substance and mixture are listed in the following table:

Characteristics	Mixture	Pure substance
Definition	A combination of two or more substances that are physically mixed but not chemically bonded.	A substance that consists of only one type of element or compound.
Composition	Can have variable composition, with different substances in different proportions.	Always has a fixed and constant composition.
Separation	Components can be separated using physical methods, such as filtration, distillation, or evaporation	Cannot be separated into different substances by physical means.
Homogeneity	May be homogeneous (uniform composition) or heterogeneous (non-uniform composition).	Homogeneous throughout (uniform composition).
Properties	The properties of a mixture are a combination of the properties of its individual components.	Exhibits unique chemical and physical properties that are characteristic of the substance.
Chemical Changes	No new substances are formed when components are mixed.	Can undergo chemical reactions to form new substances.
Examples	Examples include air (a mixture of gases), salad, and a sand and salt mixture.	Examples include elements like oxygen, compounds like water, and pure metals like gold.

Sample Questions on Pure Substance

Question 1: Is air a pure substance?

Answer:

No, Air is not a pure substance, its a mixture of gases and dust particles.

Question 2: Is water a pure substance?

Answer:

Yes, water is a pure substance in which hydrogen and oxygen are combined in a fix ratio.

Question 3: Is Sugar a pure substance?

Answer:

Yes, sugar is a pure substance in which carbon, hydrogen and oxygen are combined in a fixed ratio given as C₁₂H₂₂O₁₁

Question 4: Is milk a pure substance?

Answer:

No, milk is not a pure substance. It is a mixture of fat, water and other components

Question 5: Is salt a pure substance?

Answer:

Yes, salt is a pure substance in wich Na and Cl are combined in a fixed ratio.

Question 6: Is Gold a pure substance?

Answer:

Yes, Gold is a pure substance because it is an element represented as Au.

Question 7: Is Iron a pure substance?

Answer:

Yes, Iron is a pure substance because it is an element represented as Fe.

Question 8: Is carbon dioxide a pure substance?

Answer:

Yes, carbon dioxide is a pure substance in which carbon and oxygen are combined in a fixed ratio

Question 9: Is oxygen a pure substance?

Answer:

Yes, Oxygen a pure substance because it is an element represented by O.

Question 10: Is ice a pure substance?

Answer:

Yes, ice is a pure substance, because it is frozen or solid form of water hence its chemical composition is same as that of water i.e. H₂O

Pure Substance FAQs

Define Pure Substance.

A pure substance is a material composed of a single type of element or more than one elements in a fixed ratio.

What makes Pure Substance different from Mixture?

Pure substances have a fixed composition, while mixtures are combinations of multiple substances in any ratio.

What are the Two Types of Pure Substance?

The two types of pure substances are elements and compounds.

Is Distilled Water a Pure Substance?

Yes, distilled water is a pure substance because it is water whose composition in H₂0

Which of the following is not a Pure Substance: Air, Water, Gold?

Air is not a pure substance its a mixture of many gases

Can we Separate Pure Substance from Mixture?

Yes its possible to separate pure substance from mixture its done using processes like distillation, filtration, and chromatography