Definition types of pure substances and mixtures with separation methods and examples
Anything that has mass and that occupies some space is called matter. There are basically two types of matter, pure and impure substances. Almost everything that you see around you is all matter. However, the question which arises here is whether the matter around us is pure or not? Moreover, on what terms can you define the term purity? There would have been many instances where you would have come across sentences like the water is pure or the milk used to make the tea is pure. But is it right to say all this? Or on what grounds can you say that a substance is pure? Can you say that any substance is pure if it is smooth in consistency or feels soft or is white in color? Well, to answer all your questions we will be learning about the matter today, particularly the pure and impure substances and know the answer to the question “is matter around us pure”.
What are Pure and Impure Substances?
A substance is called to be in the pure form if it is made up of just one type of molecules or particles. Pure substances normally cannot be separated by the means of simple physical methods and are widely classified as elements and compounds. An element contains only one kind of particle that can be atoms or molecules. Similarly, compounds are pure substances when they consist of two or more elements that are combined in a fixed proportion by their weight. Additionally, pure compounds are easily decomposed to separate elements by using several suitable chemical methods.
A substance which is composed of different types of elements or molecules is called impure. These kinds of substances are often known to be mixtures. Mixtures are further classified as either homogeneous mixtures or heterogeneous mixtures based on their composition. They are mostly made pure by using different kinds of separation techniques.
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Characteristics of Pure Substance
Let us now look at some of the characteristics of pure substance.
Pure substances have a perfectly homogeneous nature.
Pure substances are made up of only one type of atoms or molecules.
Pure substances have a fixed composition.
Pure substances have a fixed density, melting point, boiling point etc.
Characteristics of Impure Substance
Let us look at the characteristics of impure substances now.
Impure substances do not have any specific properties. The properties of the resulting mixture are a result of the average properties of all its constituents.
Impure substances are formed when there is a physical change.
Impure substances have a variable composition.
The mixtures of the impure substances are either homogeneous or heterogeneous in nature.
Difference between Homogeneous and Heterogeneous Substances
Different States of Matter
The three different states of matter present on Earth are solid state, liquid state, and gaseous state. Let us look at each of them in detail.
Solids
In a solid, the particles are packed tightly together so they don't move much. The electrons of each atom are constantly in motion, so the atoms have a small vibration, however, they are fixed in their position. Because of this, the particles in a solid have very low kinetic energy.
Solids have a definite shape, as well as mass and volume, and do not conform to the shape of the container in which they are placed. Solids also have a high density which means that the particles are tightly packed together.
Liquids
In a liquid, the particles are more loosely packed than in a solid and are able to flow around each other, giving the liquid an indefinite shape. Therefore, the liquid will conform to the shape of its container.
Much like solids, liquids (most of which have a lower density than solids) are incredibly difficult to compress.
Gasses
In a gas, the particles have a great deal of space between them and have a higher kinetic energy. A gas has no definite shape or volume. If unconfined, the particles of a gas will spread out indefinitely; if confined, the gas will expand to fill its container. When a gas is put under pressure by reducing the volume of the container, the space between the particles is reduced and the gas is compressed.
Is Matter Around us Pure? - Summary
As mentioned above matter is of two different kinds, pure and impure substances. You can know the products and matter around you is pure or impure by taking a look at them and their composition. Consider, for example, salt. The constituents of all the particles in the salt are the same, that is, the particles are all NaCl. They look and taste the same as well. There is no other kind of particle present in the salt except NaCl. This means that salt is a pure substance. When you talk about impure substances, they are made up of different molecules in just one substance. Consider, for example, ghee. Ghee is made up of several vitamins, amino acids, fats, etc., and is, therefore, regarded as an impure substance. All impure substances are said to be mixtures of two or more substances or molecules.
FAQs on Is Matter Around Us Pure Complete Concept Guide
1. Is matter around us pure?
No, most matter around us is not pure and exists as mixtures rather than pure substances. A pure substance contains only one kind of particle (either an element or a compound), while everyday materials like air, milk, soil, and seawater are mixtures of different substances.
- Pure substances: Elements (e.g., O2, Fe) and compounds (e.g., H2O, CO2).
- Mixtures: Air (mixture of gases), milk (colloid), salt water (solution).
- Most natural materials are mixtures because different substances combine physically without chemical bonding.
2. What is a pure substance in chemistry?
A pure substance is a material made up of only one kind of particle and has a fixed composition and definite properties. It cannot be separated into simpler substances by physical methods.
- It may be an element (e.g., Cu, O2).
- Or a compound (e.g., H2O, NaCl).
- It has a sharp melting point and boiling point.
- Its composition is uniform throughout.
3. What is the difference between a pure substance and a mixture?
The main difference is that a pure substance has a fixed composition, while a mixture has a variable composition.
- Pure substance: Single type of particle, fixed melting/boiling point, cannot be separated by physical methods.
- Mixture: Two or more substances physically combined, variable composition, can be separated by physical methods.
- Example: H2O is pure, while salt dissolved in water is a mixture.
4. What are the types of mixtures?
Mixtures are classified into homogeneous mixtures and heterogeneous mixtures.
- Homogeneous mixture: Uniform composition throughout (e.g., salt solution, air).
- Heterogeneous mixture: Non-uniform composition with visible boundaries (e.g., oil and water, sand in water).
- Solutions are a type of homogeneous mixture.
5. What is a solution in chemistry?
A solution is a homogeneous mixture of two or more substances where one substance (solute) is uniformly dissolved in another (solvent).
- Solute: Substance being dissolved (e.g., NaCl).
- Solvent: Substance that dissolves the solute (e.g., H2O).
- Example: Salt solution is formed when NaCl dissolves in water.
- Solutions are transparent and do not scatter light.
6. What is the difference between a solution, suspension, and colloid?
A solution, suspension, and colloid differ mainly in particle size and stability.
- Solution: Particle size < 1 nm, does not scatter light, stable (e.g., salt water).
- Colloid: Intermediate particle size, shows Tyndall effect, does not settle (e.g., milk).
- Suspension: Large particles, settles on standing, can be filtered (e.g., sand in water).
7. What is the Tyndall effect?
The Tyndall effect is the scattering of light by colloidal particles, making the path of light visible.
- Observed in colloids but not in true solutions.
- Example: Light beam visible in a foggy room.
- Helps distinguish between a solution and a colloid.
8. How can we separate the components of a mixture?
The components of a mixture can be separated by physical methods based on differences in physical properties.
- Filtration: Separates insoluble solids from liquids.
- Evaporation: Recovers dissolved solids from solutions.
- Distillation: Separates liquids based on boiling points.
- Chromatography: Separates components based on differential adsorption.
9. What is the difference between an element and a compound?
An element contains only one type of atom, while a compound contains two or more elements chemically combined in a fixed ratio.
- Element: Cannot be broken down chemically (e.g., Fe, O2).
- Compound: Can be decomposed chemically (e.g., H2O).
- Example reaction: 2H2(g) + O2(g) → 2H2O(l).
10. Why do pure substances have fixed melting and boiling points?
Pure substances have fixed melting and boiling points because they consist of identical particles with uniform intermolecular forces.
- All particles require the same amount of energy to change state.
- Example: Pure water boils at 100°C (373 K) at 1 atm pressure.
- Mixtures boil over a range of temperatures due to varying composition.
