Elements, Mixtures, Elements, Mixtures, Compounds and Compounds and

SolutionsSolutionsIntroduction to ChemistryIntroduction to Chemistry

What is Chemistry?What is Chemistry?

•Chemistry is the study of elements and the compounds they form.

Conservation of MassConservation of Mass

• The Law of Conservation of MatterLaw of Conservation of Matter states that matter can not be created or destroyed.– Like energy, however, matter can change

forms.

Properties of MatterProperties 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 MatterProperties of Matter

• Chemical propertiesChemical properties of a substance describe the arrangement of elementselements that the substance is made of.

• A chemical changechemical 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?What is an Element?

• An elementelement 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 Elements Can Be CombinedCombined

• When elements are combined several things can result:– A mixturemixture– A chemical reactionchemical reaction– A compoundcompound– A solutionsolution

What is a Mixture?What is a Mixture?

• A mixturemixture 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 mixturemixture can be separated by the

differences in the physical properties of the elements that have been mixed.

Separating MixturesSeparating Mixtures

• A mixture can be separated by a number of means such as

•EvaporationEvaporation•DistillationDistillation•FiltrationFiltration•Differences in solubilitysolubility

What is a Chemical What is a Chemical Reaction?Reaction?

•A chemical reactionchemical 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 Types of Chemical ReactionsReactions

• Exothermic reactionsExothermic reactions are reactions that give off heatgive off heat. – These reactions feel warm/hot since they

are releasing heat into the surroundings.

• Endothermic reactionsEndothermic reactions are reactions that absorb heatabsorb heat.– These reactions feel cool/cold since they

are pulling in heat from the surroundings.

Exothermic and Endothermic Reactions

What is a Compound?What is a Compound?

• When a chemical reaction does take place, the two elements form a compoundcompound.

• The compoundcompound has physical and chemical properties that the individual elements did not have.

• The two elements in a compound can only be separated by another can only be separated by another chemical reactionchemical 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 ?What is pH ?

• One characteristic of a solution is its pH valuepH value. Solutions can be acidic or basic.

• The pH scalepH scale is used to indicate if a solution is acidic or basic, and to tell us the strength of the acid or base.

• The pH scalepH scale is a range from 0 to 14 with 7.0 representing neutral (neither acidic or basic).

AcidsAcids

• 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.

BasesBases

• 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.