Matter surrounds us, and chemistry is the science of matter and its interactions. Chemists classify matter as either a pure substance or a mixture. A pure substance is one that is made up only one kind of matter or particle. Two or more pure substances or types of particles make up mixtures.
About Pure Substances in Chemistry
A pure substance is matter that has a definite composition and cannot be separated by physical means. Gold, water, and oxygen are all pure substances. We can explain many properties of matter can by using the particle model, but what are these particles?
Two hundred years ago, scientists already knew of thousands of pure substances and were constantly discovering more. They hoped that by breaking down these substances, they would discover the building blocks of mater – the particles that Democritus suggested could not be broken down any further.
Once scientists knew all the building blocks, they believed that they would be able to predict the properties of a pure substance from the properties of the “blocks” or “particles” of which it was made. As a result of these efforts, scientists now know of over 100 of these building blocks which they call elements.
There are two types of pure substances: elements and compounds. Elements are pure substances that cannot be broken down or separated into simpler substances by chemical means. Compounds are pure substances that contain two or more different elements in a fixed proportion.
Hydrogen and oxygen are two elements which forms the compound water when the elements combine together in a chemical reaction. A compound may have completely different properties from each of the elements.
An Introduction to Mixtures and their Categories
Most of the materials we interact with each day are mixtures. A mixture is a blend of two or more substances in which each substance retains its individual properties. When two pure substances are mixed together, sometimes they mix smoothly and sometimes they mix unevenly.
Imagine you have to identify a glass with a substance that you think is a mixture. What type of mixture might it be? Perhaps your mixture is sugar and water where the particles mix uniformly throughout, and you cannot see their components, even with a microscope. If the particles mix very well with one another – so that you can see only one phase or visible part – the mixture is called a solution and is classified as a homogeneous mixture. We say that one substance dissolves in another. Air, steel, diesel fuel are examples of homogeneous mixtures.
When you make a pizza, tomato sauce, cheese, mushrooms, and pepperoni are mixed together or scattered on top of the crust. You can see the different parts easily. You can say that the particles do not mix well with one another and you are able to see more than one phase. We call this type of mixture a heterogeneous mixture. Another heterogeneous mixture is the rock on a hillside which may include quartz, a compound that is made of the elements silicon and oxygen.
Examples of Pure Substances
Many of the basic essential raw materials that we use in our daily lives and are fundamental for economic, social and technological development are minerals. Minerals are pure substances which contain one or more elements, and cannot be broken down into simpler substances by chemical means. They are non-renewable natural resources that are vital for the construction, technological, manufacturing and energy industries.
Some important minerals include phosphate, potash and lime that are used in agricultural fertilizers. Minerals such as iron, copper, nickel, limestone, silica are used in construction for building houses, schools and hospitals.
Total mineral exploration expenditures in Canada was between $750 and $850 million in 1990. A total of 3276 mineral from five mineral types have been identified on land belonging to First Nations people. This sector has the potential to be a major contributor to the economic growth of First Nations people as they would benefit from the economic development of the mineral resources on or near their lands.
Many First Nations communities have experienced some form of development work related to their mineral resources. Opportunities may be translated in terms of work permits and leases, joint ventures, spin-off businesses such as trucking, catering or prospecting, self or full time employment, new training initiatives and career development.
Traditional Mixtures that Provide Healing
The use of mixtures have been the foundation traditional healing worldwide, probably from humans’ earliest beginnings. In Canada, stories passed down through the Elders record that the Indigenous peoples have been mixing herbs to make medicine for hundreds of years. Herbal medicine may contain a mixture of naturally occurring substances from a part of a plant or a substance extracted from a plant such as a sap or an oil.
It is well documented that a substance in willow bark, originally employed by First nations healers, was used as pain reliever for years. This substance is known by it chemical name, acetylsalicylic acid, commonly called Aspirin®.
The derivation of traditional medicines did not occur by accident or through trial and error. In Saskatchewan, First Nations and Métis peoples have used herbal medicines, in combination with prayer and ceremony for many generations. Medicine women would go on a fast for several days during which time they would meditate on the medicines and plants they would mix to create the desired effects.
The healing tradition of the First Nations and Métis peoples is a holistic process that includes, physical, mental emotional, and spiritual healing. Certain families have spiritual understanding of mixing medicines for heart disease, diabetes, hepatitis, and other illnesses. Today Elders are concerned about the way some pharmaceutical companies can exploit traditional medicines as they search the natural world for plant extractions they can patent as new drugs.
Bio-prospecting is the search for valuable chemical products in natural biological resources to use as an important source of novel chemical and biological products for medicine, agriculture, and other industries. This means that pharmaceutical companies take plants, often along with associated indigenous science and knowledge, from their natural environment so that intellectual property can be assigned to a corporation for the purpose of profit. Very often, little or no compensation goes to the communities where the plants originated. This includes communities where the majority of the population continue to rely on herbal medicines for primary care.
The Conclusion of the Matter
It is important to understand the classification of matter to know why all liquids are not the same; all solids are not the same; and all gases are not the same, in terms of chemical compositions. We need pure substances to carry out chemical reactons without impurities, in chemical research and medicine.
Separating substances from mixtures is an important part of chemistry and modern industry. Since most substances are naturally found as mixtures it is important to be able to separate mixtures to obtain desired components and to better understand how each component contributes to the properties of the resulting mixture. Studies of biochemical systems, environmental analysis, pharmaceutical research and many areas of research rely on reliable understanding of the methods used in the separation of mixtures.