Elements, Mixtures, Compounds and Solutions Introduction to Chemistry

What is Chemistry? Chemistry is the study of elements and the compounds they form.

Conservation of Mass Law of Conservation of MatterThe Law of Conservation of Matter states that matter can not be created or destroyed. –Like energy, however, matter can change forms.

Properties of Matter Physical propertiesPhysical properties are the observable characteristics of a substance, including the state of matter. Physical changesPhysical changes usually involve a change in state of matter. –Example is ice (s) melting into water (l).

Properties of Matter Chemical properties elementsChemical properties of a substance describe the arrangement of elements that the substance is made of. chemical changeA chemical change involves the rearrangement of the atoms of elements to form substances with different physical and chemical properties than the individual elements.

What is an Element? An e ee element is the simplest form of a substance that retains the properties of that substance. To break elements down any smaller would result in protons, neutrons and electrons.

Elements Can Be Combined When elements are combined several things can result: mixture –A mixture chemical reaction –A chemical reaction compound –A compound solution –A solution

What is a Mixture? A m mm mixture is made up when two or more elements are combined and the properties of the elements are retained. (No chemical reaction has taken place.) –A–A m mm mixture can be separated by the differences in the physical properties of the elements that have been mixed.

Separating Mixtures A mixture can be separated by a number of means such as EvaporationEvaporation DistillationDistillation FiltrationFiltration solubilityDifferences in solubility

What is a Chemical Reaction? chemical reactionA chemical reaction occurs when two elements are combined and form a compound that has physical and chemical properties that the elements alone did not have.

Types of Chemical Reactions Exothermic reactions give off heatExothermic reactions are reactions that give off heat. –These reactions feel warm/hot since they are releasing heat into the surroundings. Endothermic reactions absorb heatEndothermic reactions are reactions that absorb heat. –These reactions feel cool/cold since they are pulling in heat from the surroundings.

Exothermic and Endothermic Reactions

What is a Compound? compoundWhen a chemical reaction does take place, the two elements form a compound. compoundThe compound has physical and chemical properties that the individual elements did not have. can only be separated by another chemical reactionThe two elements in a compound can only be separated by another chemical reaction.

What is a Solution? A solution is a mixture of a liquid (the solvent) with a gas or a solid (the solute). In a solution the molecules of the solute are discretely mixed with the molecules of the solvent.

What is pH ? pH valueOne characteristic of a solution is its pH value. Solutions can be acidic or basic. pH scaleThe pH scale is used to indicate if a solution is acidic or basic, and to tell us the strength of the acid or base. pH scaleThe pH scale is a range from 0 to 14 with 7.0 representing neutral (neither acidic or basic).

Acids Solutions with a pH of 0.1 to 6.9 are said to be acidic. Solutions are acidic because they have the ability to release hydrogen (H + ) into solution. pH values closest to 0 are the strongest acids.

Bases Solutions with a pH of 7.1 to 14 are said to be basic or alkaline. Solutions are alkaline because they have the ability to release hydroxide (OH - ), or accept hydrogen, into solution. pH values closest to 14 are the strongest bases.