General and Inorganic Chemistry Prof. Maurizio Paci Phone:

Chemistry and Matter Chemistry “The study of properties of materials and of changes that materials undergo” Matter “It’s the physical material of universe; anything that occupies space and has mass” Matter can exist in three physical states (aggregation states): 1.Gas o vapor 2.Liquid 3.Solid

Introduction to Matter Gas No fixed volume or shape; it conforms to the volume and shape of its container. Gases can be compressed or expanded to occupy different volumes Liquid A liquid has a fixed volume, independent of its container, but it has no specific shape. It assumes the shape of the container it is in. Liquids cannot be appreciably compressed Solid A solid has its own defined volume and shape. Solids cannot be appreciably compressed

Introduction to Matter Substance A pure substance has a fixed composition and distinct properties. Most matter we come in contact with in daily life is not a pure substance but a mixture of different substances Physical and Chemical Properties Every pure substance has a unique set of defined properties : characteristics which allow us to distinguish it from other substances. These properties fall into two general categories: physical and chemical. Changes can be macroscopic or microscopic Chemical Properties – properties that we can measure without changing the basic identity (the composition) Chemical Properties – describe the way a substance can change or react to form other substances

Introduction to Matter Physical and Chemical Changes Substances can undergo several changes in properties; these changes can be classified as either chemical or physical Physical changes– changing the physical appearance but not the basic identity. All changes of state (e.g. solid, liqid or gas) are physical changes Chemical changes– also known as chemical reactions. Changing the basic identity: the substance is tranformed into different chemically substances.

Introduction to Matter Mixtures Mixtures refer to combination of two or more pure substances in which each substance retain its own chemical identity and hence its own properties Heterogeneous mixtures are not uniform throughout the sample and have regions of different appareance and properties Homogeneous mixtures are uniform throughout the sample, however the individual substances retain their individual chemical and physical nature. Homogeneous mixtures are also called solutions. The most common type is descrbed by a solid (the solute) that is dissolved in a liquid (the solvent) An important characteristic of homogeneous mixtures is that individual components retain their chemical and physical properties. Thus, it’s possible to separate the substances based on their different physical properties For example, we can separate water from ethanol using heir different boiling temperatures in a process known as distillation.

Elements and compounds Pure substances have an invariable composition and are composed by either elements or compounds Elements Substances that cannot be decomposed into simpler substances by chemical means Compounds Can be decomposed into two or more elements, by which that substance is constituetd.

Elements and compounds

Elements Elements are the basic substances out of which all matter is composed Everything in the worls is made up of only 109 different elements 90% of the human body is composed by only three elements: Oxygen, Carbon and Hydrogen Elements are known by a common name as well as their abbreviation.

ElementAbbreviation CarbonC FluorineF HydrogenH IodineI NitrogenN OxygenO PhosphorusP SulfurS AluminumAl BariumBa CalciumCa ChlorineCl HeliumHe MagnesiumMg PlatinumPt SiliconSi CopperCu (from cuprum) IronFe (from ferrum) LeadPb (from plumbum) MercuryHg (from hydrargyrum) PotassiumK (from kalium) SilverAg (from argentum) SodiumNa (from natrium) TinSn (from stannum)

Elements and compounds Compounds Compounds are substances composed by two or more elements. In a compound the constituting elements are chemically united and are combined in a definite proportion by mass. The observation that the elemental composition of a pure compound is always the same is known as the law of constant composition ( or the law of definite proportions). For example, pure water is composed by two elements, Oxygen and Hydrogen, at the defined ratio of 11% Hydrogen and 89% Oxygen. In one kg of water we find 110 g of H and 890 g of O. In 20 g of water there are 2.2 g of H and 17.8 g of O