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Elements, Compounds and Mixtures

Can iron be converted to gold?? Can iron be converted to gold? Alchemists are the chemists of ancient times who tried to transform base metals such as iron to the noble metal gold. The word 'alchemist' comes from a Greek word, 'Khemeia' that means art of transforming metals. The chemists believed that gold is the most stable metal and every element tend to convert into gold. Their theory is based on ability of philosopher’s stone (also called elixir). However, it is a myth and scientists proved that an element can not be converted into another element through a chemical process.

Learning Objectives

After completing the topic, the student will be able to:

  • Define the element, compound and mixture which are the chief components of matter.
  • Differentiate element, compound and mixture.
  • Separate the mixtures by different methods such as filtration, distillation etc.
  • Classify the given matter into different substances such as pure element or compound.
  • Distinguish the homogeneous and heterogeneous mixtures.
  • Predict whether the given mixture is homogeneous mixture or heterogeneous mixture.
  • Compare the properties of mixture, suspension and colloids.
Transforming matter Matter exists in three different states at room temperature. These are solid, liquid and gaseous states. The three states of the matter are inter-convertible when heat is supplied or removed from molecules. For example, water at ordinary temperature is liquid. But if we cool it, it becomes ice and on heating it gives steam.
Two other forms also exist at extreme temperatures. These are plasma and Bose–Einstein condensate that occur at a very high (105K) and very low (<10–7 K) temperatures respectively.
Matter

All substances around us consist of matter. Matter is anything that occupies space and has mass. The blackboard in the classroom, the chair that you are sitting on, the air you breathe, the food you eat, the plate and spoon, etc., are all made up of matter. All living and non–living objects−everything is made up of matter!

What do you first observe about matter? Our perception and understanding of everything around us is through our five different sense organs−eyes, nose, ears, tongue and skin. We see that matter comes in various colors, smells, textures, temperatures etc. Edible matter comes in various tastes and if you hit various objects, they make many different sounds. The variety of matter is immense and exist in various states. In addition, matter (or substances) can be either pure or a combination of two or more substances. For example, water may be a pure liquid, but salt solution is a combination of water and salt.

Besides these properties, matter, as seen in everyday life, comes in three primary states: solid, liquid and gas. The simplest observation is water cycle. Water as rain is liquid and as hail is solid. The third state is the invisible water-vapour (steam) due to evaporation by Sun rays.

Heat plays a crucial role in transforming matter from one state into another. Each transformation has a specific name and purpose (refer adjacent image). For example, a solid can be transformed into liquid by a transformation process, melting. In addition, matter (or substances) can be either pure or a combination of two or more substances. For example, water may be a pure liquid, but salt solution is a combination of water and salt.

On heating, the chemicals in the fireworks ignite and form compounds that display various colours. When Sodium (Na) is ignited, it reacts with oxygen in the air to give golden yellow flame.
Charring of sugar On reacting with strong acid or heating, the water in the sugar separates as vapours. A column of black carbon (called char) grows up from the beaker. Separation of water and carbon indicates sugar is a compound. Water is a molecule (single compound) as it can be further separated (by electrolysis) into its components: Hydrogen (H) and Oxygen (O). Therefore, in this experiment, Carbon is the only element separated from its compound.
Composition of matter

What makes matter exhibit these physical states? Probably, its components. For better understanding, let us consider a piece of chalk and go on cutting it into smaller and smaller bits. We will come to a stage where, a microscope is needed to see the dimensions of the smallest particles of matter, known as molecules. A molecule of chalk is made up of further smaller components, the atoms.

Elements that exist as individual atoms are called mono atomic. Examples: Helium, Neon etc. Based on the number of atoms that combine, molecules are classified as di-atomic, tri-atomic and poly-atomic molecules. For example, Hydrogen is diatomic, Oxygen in Ozone is tri-atomic while, Sulphur is polyatomic. Combination is also observed between two different atoms like Hydrogen and Oxygen to form water (Symbol: H2O). Such molecules are called compounds.

Compounds are always made of different types of atoms while molecules are made of either similar or different types of atoms. Molecule of Hydrogen (H2) is not a compound as it is composed of a single element, while Carbon dioxide (CO2) is a compound and molecule because of having more than an element.
So, all compounds are molecules but all molecules are not compounds.

The difference in properties exhibited by compounds (or molecules) is due to difference in their chemical composition i.e, arrangement of chemical components like atoms or ions that make up the matter.
Examples:
i. The properties of steel like hardness and tensile strength depend upon mainly the arrangement of carbon with iron. Hence it is used in making rail tracks.
ii. The alloy Duralumin is made of chemicals like aluminium, copper, magnesium and manganese. It is extremely hard and yet very light. It serves as a basic material for the manufacture of aircraft and its accessories.

An element is a pure substance that cannot be split into two or more simpler substances by applying heat, light, electric energy or chemical reactions. They are characterised by the atoms that have a fixed number of sub-atomic particles. A relation between various components of matter is explained using ice that is made of oxygen and hydrogen atoms. When it is viewed through a powerful microscope, bonded atoms of different elements are visible. Observe that atoms combine to form a molecule.

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