Elements, Mixtures and Compounds - Essay Example

For example, a mixture of iron and sulfur can be taken in any proportion while a compound such as iron (II) sulfide always has a ratio of 7 : 4 by mass of iron and sulfur (Leong & Aik, 2009). When a mixture is prepared by mixing two or more substances, there is no chemical exchange involved and there is absence of heat or light production. When a compound is prepared, it is usually accompanied with a chemical change in which some heat, light or both are liberated. For example, when a mixture is prepared by mixing iron filings and sulfur, no heat is liberated.

However, when hot iron filings and sulfur are taken together in a test tube, a chemical reaction occurs resulting in the formation of iron sulfide (Fe + S ?FeS). The test tube glows red because of heat produced during the reaction (Leong & Aik, 2009). The properties of a mixture are characteristic of the individual substances mixed. On the contrary, the properties of a compound are very different from those of the original elements. For example, in a mixture of iron filings and sulfur, properties such as magnetism, color, texture of the individual substances are retained.

Iron sulfide, a compound, has very different properties from those of iron and sulfur. It lacks magnetic activity and also has different physical and chemical properties (Leong & Aik, 2009). . 2) Supposed that you have a pure substance, how can you tell whether it is a compound or an element?  An element cannot be further broken down chemically, while a compound can be broken down into individual components or elements using chemical reactions specific for that compound. For example, heating mercuric oxide, which is a compound, over a Bunsen flame, will result in the decomposition and separation of mercuric oxide into mercury and oxygen.

However, mercury and oxygen, which are elements, cannot be further broken down using any chemical means (Leong & Aik, 2009). Therefore, in order to tell whether a given pure compound is an element or a compound, it will be subjected to various separation procedures to determine if it can be broken down further. Its melting and boiling points and other physical and chemical properties will also be noted and compared with those of preexisting elements and compounds for ease of identification. 3) What is the difference between an ionic and a covalent bond?

Chemical bonds such as ionic and covalent bonds determine the properties of a compound. The main differences between the two kinds of bonds are discussed as follows: Ionic bond is formed when electrons are transferred from one atom to another. The transfer of electrons results in the formation of a positive and a negative ion that are held together by strong electrostatic attraction. For example, salt (NaCl) is formed when an electron from sodium (Na) is transferred to chlorine (Cl) to form ions (Na+ and Cl- ) that are held together to form salt (NaCl).

Covalent bond is formed when an electron pair from the outer shell is shared between two atoms. For instance, Hydrochloric acid