A chemical reaction is the change of a substance into a new one which has a different chemical identity. Usually, a chemical reaction is accompanied by simply observed physical effects, such as the formation of a precipitate, the emission of heat and light, the evolution of gas, or a color change. You have to note that absolute confirmation of a chemical change is only able to be validated by chemical analysis of the products.
CHEMICAL MIXTURES
A mixture is a material system created up of two or more different substances, that are mixed but not combined chemically. A mixture indicates the physical combination of 2 or more substances in which the identities of individual substances are retained. Mixtures take the form of alloys, colloids. solutions, and suspensions. Crystal sulfur occurs naturally as elemental sulfur, sulfide, and sulfate minerals and in hydrogen sulfide. Mineral deposit is structured of a mixture of substances.
Apparently, there are two types of mixtures: Heterogeneous mixture and homogeneous mixture. In the text below, you are able to find out its explanation.
HETEROGENEOUS MIXTURES
A heterogeneous mixture is a mixture of two or more chemical substances (compounds or elements), where the different components are able to be visually distinguished and separated easily by physical means. Examples include:
- Mixtures of water and sand.
- Mixtures of iron filings and sand.
- Mixtures of silver powder and gold powder.
- A conglomerate rock.
- Oil and water.
- Trail mix
- A salad
For your information, oil and water explore the interactions which cause oil and water to separate from a mixture.
HOMOGENOUS MIXTURES
A homogeneous mixture is a mixture of two or more chemical substances (compounds or elements) where the different components cannot be visually distinguished. The composition of homogeneous mixtures is constant. Frequently separating the components of a homogeneous mixture is more challenging than separating the components of a heterogeneous mixture.
DISTINGUISHING BETWEEN HOMOGENEOUS AND HETEROGENEOUS MIXTURES
Based on the research, distinguishing between homogeneous and heterogeneous mixtures is a matter of the scale of sampling. In a small scale, any mixture is able to be said to be heterogeneous, as a sample can be as small as a single molecule. In practical terms, if the property of interest is the same regardless of how much of the mixture is taken, so the mixture is homogeneous. A mixture’s physical properties, such as its melting point, can differ from those of its individual components. Several mixtures are able to be separated into their components by physical means.
MIXTURES AND COMPOUNDS
However, there are some sources state that mixtures have different properties from compounds. In the table below summarises those differences.
| Mixture | Compound | |
| Composition | Variable composition. You are able to differ the amount of each substance in a mixture. | Definite composition. You cannot differ the amount of each element in the compound. |
| Joined or not joined | The different substance is not joined together chemically. | The different compounds are chemically joined together. |
| Properties | Each substances in the mixture keep their own properties | The compounds have properties that are different from the elements. |
| Separation | Each substance is separated from the mixture easily. | It is only only able to be separated into its elements using chemical reactions. |
| Examples | Air, most rocks and sea water. | Water, magnesium oxide, sodium chloride and carbon dioxide. |
Now, we are going to explain an example of iron, sulfur and iron sulfide.
Iron and sulfur react together once they are heated to create a compound named iron sulfide. By the way, what are the differences between a mixture of iron and sulfur, and iron sulfide? Here are some of them:
- The mixture is able to contain more or less iron, but iron sulfide contains equal amounts of iron and sulfur.
- The iron and sulfur atoms are not joined in the mixture together. However, they are joined together in iron sulfide.
- The iron and sulfur behave like iron and sulfur in mixture. However, iron sulfide has different properties from sulfur and iron.
- You are able to separate the iron from the mixture by using a magnet, but this does not work for iron sulfide.
CHEMICAL SUBSTANCES
A chemical substance is a form of matter which has chemical composition and properties. It cannot be separated into components without breaking the chemical bonds. Chemical substances are able to be liquids, solids, gases, or plasma. Changes in temperature or pressure are able to cause substances to shift between the different phases of matter.
An element is a chemical substance which is made up of a particular kind of atom. Therefore, cannot be broken down or transformed by a chemical reaction into a different element. All atoms of the element have the same number of protons, even though they have different numbers of neutrons and electrons. A pure chemical compound is a chemical substance which is composed of a particular set of molecules or ions which are chemically bonded. Two or more elements combined into one substance through a chemical reaction, like water, form a chemical compound. All compounds are substances, however not all substances are compounds. A chemical compound is able to be either atoms bonded together in molecules or crystals in which atoms, ions and molecules form a crystalline lattice. Compounds created primarily of carbon and hydrogen atoms are named organic compounds. All others are named inorganic compounds. Compounds containing bonds between metal and carbon are named organ metallic compounds.
Frequently, chemical substances are called ‘pure’ to set them apart from mixtures. An example of a chemical substance is pure water which always has the same properties and the same ratio of hydrogen to oxygen whether it is isolated from a river or made in a laboratory. Commonly other chemical substances encountered in pure form are diamond, gold, table salt and refined sugar. Simple substances that are found in nature are able to be mixtures of chemical substances. For example, tap water can contain small amounts of dissolved sodium chloride and compounds which contain calcium, iron, and many other chemical substances. While pure distilled water is a substance, but seawater as it contains ions and complex molecules.
