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Matter is one of the most fundamental topics of chemistry. It occupies a certain space and have mass. The air you breathe, the water you drink, or the clothes you wear are forms of matter. The matter is made up of an elementary particle referred to as an atom.
Furthermore, matters are divided into two major categories, including the pure substances and impure substances. Pure and impure substances differ from each other and have distinctive characteristics.
What are pure substances?
Pure substances are formed with a combination of single types of atoms. Therefore, it can be said that pure substances have homogeneous chemical compositions and hold a fixed structure and unique chemical properties. Further, pure substances are divided into two major categories. These include –
- Elements
Elements are often described as pure substances as they only contain a single type of atom. Presently, there are about 118 elements in the periodic table, out of which some of the most common ones are silver (Ag), gold (Au), sulphur (S), hydrogen (H), and so on.
- Compounds
When more than one element combines chemically in the fixed ratio, a compound is formed. Pure compounds can be chemically transformed into newer substances. Some common examples of these substances include salt (NaCl), carbon dioxide (CO₂), water (H₂O), and so on.
Properties of pure substances
The following are the properties of pure substances –
- Pure substances have homogeneous chemical compositions.
- These have constant structures and unique chemical properties.
- They possess a defined melting and heating point .
- They are further divided into two major parts, including compounds and elements.
Examples of pure substances
Here are some more examples of pure substances –
- Sugar (C₁₂H₂₂O₁₁),
- Chlorine (Cl₂),
- Baking soda (NaHCO₃),
- Oxygen (O₂), etc.
What are impure substances?
There are different types of molecules or atoms that together make impure substances, also known as mixtures. The stature of these is not fixed or constant, unlike pure substances. They can be broken down into pure substances with the help of purification methods like sublimation, filtration, crystallisation, and so on. Further, impure substances are classified into two major categories –
- Homogeneous mixture
Homogeneous mixtures can be described as a mixture where the substances mixed together are distributed uniformly throughout the mixture. The amount of substances present in every sample of a homogeneous mixture is always the same. In this mixture, only a single phase of matter is observed. The most common examples of Homogeneous mixtures include sugar water, rainwater, air, vinegar, and vodka.
- Heterogeneous mixture
Heterogeneous mixtures are mixtures in which different substances or components are mixed together and are clearly visible under the microscope. Their components can be easily identified through the naked eye.
Here is a quick difference between a homogenous mixture and the heterogeneous mixture for the ease of revision –
Homogeneous mixture | Heterogeneous mixture |
The homogeneous mixture has a uniform composition. | The heterogenous mixture does not have a uniform composition. |
The homogeneous mixture has a single phase. | There are either two phases in the heterogeneous mixture or more than that. |
The homogeneous mixture can not be separated, if tired physically. | Separation of heterogeneous mixture is possible physically. |
The word ‘homo’ is referred to as the same. | ‘Hetero’ is refered to different. |
For example: The mixture of water and alcohol. | For example: The mixture of sand and sodium chloride. |
Properties of impure substances
The following are the properties of impure substances –
- Impure substances have heterogeneous chemical compositions.
- These substances are formed because of chemical changes.
- These can be transformed into pure substances by purification methods such as crystallisation, filtration, sublimation, and so on.
- Impure substances are further divided into homogeneous and heterogeneous mixtures.
Examples of impure substances
Other popular examples of impure substances are as follows –
- Rocks,
- Sand in water,
- Salad,
- Coffee,
- Sugarcane juice.
Difference between pure and impure substances
Below, we have curated a table that signifies the difference between pure and impure substances. Let us have a look –
Pure substances | Impure substances |
Pure substances compose a single type of atom or molecule. | Impure substances are made of different types of atoms or molecules. |
These are subdivided into elements and compounds. | These are subdivided into homogeneous and heterogeneous mixtures. |
They have homogeneous chemical composition. | They have varying or heterogeneous chemical composition. |
Pure substances cannot be broken down into simpler substances. | Can be broken down into purer forms by using separation or purification techniques, like filtration, sublimation, etc. |
Pure substances have a fixed structure. | Their structure is not constant or fixed. |
Conclusion
Matter is one of the most fundamental topics in chemistry. It can be divided into two broad groups based on their composition. Pure and impure substances are two different types of matter. You come across many such substances in your everyday life. Both have their own sets of unique characteristics and compositions.
The air you breathe, the water you drink, or the clothes you wear are forms of matter. These notes on the characteristics of pure and impure substances provide a detailed understanding of these substances. Moreover, the pure and impure substances difference table gives a quick glimpse for easy revision.
