Chapter 4 Material on Midterm

 What colors make up black ink?

 Objectives ◦ Describe pure substances ◦ Describe the characteristics of elements, and give examples ◦ Explain how elements can be identified ◦ Classify elements according to their properties

 The simplest substance? An element! ◦ An _____________ is a pure substance that cannot be separated into simpler substances by physical or chemical means  A ___________________________ is a substance in which there is only one type of particle  Called ___________ element Pure substance atoms

 Properties of Elements ◦ Identified by their characteristic properties  Do not depend on the ______________ of a substance  Boiling point  Melting point  Density  Reactivity  No two elements have the same atoms  May need more than one property to identify amount

They are listed on the Periodic Table of Elements. Each element can be identified by its physical properties and chemical properties.  Most elements are solids at room temperature (20°C).  11 are gases.  2 are liquids.  All elements are represented by universally recognized symbols

CobaltIronNickel Melting Point: 1495 C Melting Point: 1535 C Melting Point: 1455 C Density: 8.9 g/cm 3 Density: 7.9 g/cm 3 Density: 8.9 g/cm 3 Conducts electric current and heat energy Unreactive with oxygen in the air Combines slowly with oxygen in the air to form rust Unreactive with oxygen in the air

Example: Dog Breeds How do you tell one breed from the other? Three categories of elements. Elements are organized on the Periodic Table by similar properties.

 Classifying Elements by their Properties ◦ Three main categories  _______________ are elements that are shiny and good conductors of heat and electricity  _________________ are elements that conduct heat and electricity poorly  ___________________ are elements that have both properties of metals and nonmetals Metals Nonmetals Metalloids

 Section Review ◦ Please answer the objectives on your summary sheet 1.Describe pure substances 2.Describe the characteristics of elements, and give examples 3.Explain how elements can be identified 4.Classify elements according to their properties

 Objectives ◦ Explain how elements make up compounds ◦ Describe the properties of compounds ◦ Explain how a compound can be broken down into its elements ◦ Give examples of common compounds

 What are compounds? ◦ A compound is a pure substance composed of two or more elements that are ______________ combined  As a result of a ______________ chemically reaction

 Compounds – ◦ a substance made up of atoms of two or more elements chemically combined by chemical bonds.  When elements combine, they chemically react and undergo a chemical change.

CompoundElements Combined _________________ Sodium and Chlorine __________ Hydrogen and Oxygen VinegarHydrogen, Carbon, and Oxygen _____________________ Carbon and Oxygen Baking sodaSodium, Hydrogen, Carbon, and Oxygen Sodium chloride Water Carbon dioxide

 The Ratio of Elements in a compound ◦ A compound is a pure substance ◦ The ratios in a compound are ALWAYS THE ________ ◦ EX: Water is ____________  The water to oxygen mass has a ratio of 1: 8  Same in 1 drop to 100 gallons  Different ratio? _________________! SAME H2OH2O NOT WATER

 Properties of Compounds ◦ Compounds have their _______ physical and chemical properties  EX: melting point, density, color  Physical or chemical?  EX: reactivity, flammability  Physical or chemical? OWN

 Properties Compounds versus Elements ◦ A compound will have different ______________ than the elements that make it up properties

Sodium  Soft  Silvery, white metal  Reacts violently with Chlorine Gas Poisonous Greenish-yellow

You get…….. NaCl = Table salt!

 Breaking Down Compounds ◦ Compounds can _____________________ into  Smaller compounds  Elements ◦ Must be done by a _______________ change  Add heat energy  Add electric energy break down chemical

 The only way to break down a compound is through a chemical change.  Energy is needed for a chemical change to happen.  2 ways to add energy to break a compound ◦ 1. apply heat ◦ 2. apply an electrical current

 Section Review ◦ Please answer the objectives on your summary sheet 1.Explain how elements make up compounds 2.Describe the properties of compounds 3.Explain how a compound can be broken down into its elements 4.Give examples of common compounds

 Objectives ◦ Describe three properties of mixtures ◦ Describe methods of separating the parts of a mixture ◦ Analyze a solution in terms of its solute and solvent ◦ Describe factors that affect solubility for solids, liquids, and gases ◦ Explain how concentration affects a solution ◦ Describe the particles in a solution, suspension, and colloid ◦ Explain the difference between colloids, solutions, and suspensions

 What is a mixture? ◦ A mixture is a combination of two or more substances that are _______________________________  No chemical reaction  No compound formed  Each substance keeps its original ______________  Examples: pizza, sugar water, Italian dressing, sand, concrete not chemically combined identity

Heterogeneous MixtureHomogeneous mixture  a type of mixture in which the parts of the mixture are noticeably different from one another. ◦ Ex. Trail mix, pizza, Italian dressing  a type of mixture in which the substances are so evenly distributed that it is difficult to distinguish one substance in the mixture from another. ◦ Ex. Sugar water, concrete

 Separating mixtures ◦ Use _____________ means ◦ Can take more than one step physical

 Distillation – a process that separates substances in a solution by using their boiling points.  Magnetism can be used to separate magnetic substances (Iron, Cobalt, and Nickel) from non- magnetic substances.

 Filtration - a process to separate materials based on their size. Ex: coffee filters and a screen to find artifacts at a historical site.  A Centrifuge can separate substances based of their densities. ◦ Denser materials separate first.

 The Ratio of Components in a Mixture ◦ No fixed ratio—______ always the same not

 Comparing Mixtures and Compounds MIXTURESCOMPOUNDS Made up of elements, compounds, or ________ Made of _____________ _________________ in original properties of components _____________ in original properties of components Separated by ___________means Formed using ____ ratio of components Formed using a _____ ratio of components elements both No changeChange physical chemical anyset

 What is a solution ◦ A solution is a mixture that appears to be a single substance  ____________ be filtered, cannot scatter light ◦ Who is who?  The ______________ is the substance that is dissolved  The _____________ is the substance in which the solute is dissolved Cannot solute solvent

 Solutions form when the solute dissolves in the solvent ◦ If it ________ dissolve, its soluble ◦ If it _____________ dissolve, it is insoluble does doesn’t

Solute StateSolvent StateExamples Gas Dry air (oxygen in nitrogen) GasLiquidSoda (carbon dioxide in water) Liquid Antifreeze (alcohol in water) SolidLiquidSalt water (salt in water) Solid Brass (zinc in copper)

 Concentration of Solutions ◦ The concentration is a measure of the __________ of solute in a solvent  Units: g/mL ◦ Lots of solute  __________________ ◦ Little solute  _______________ amount concentrated dilute

 What is solubility? ◦ The solubility is the ability of a solute to ____________ in a solvent at a certain temperature dissolve

 How does temperature affect solubility? ◦ For liquid solvents  A higher temperature makes a gas _______ soluble  A higher temperature makes a solid _______ soluble  USUALLY  A higher temperature makes a liquid more soluble less more

◦ To get solids to dissolve faster… Mix, stir, or shake Heat Crush

 What is a suspension? ◦ A suspension is a mixture in which particles are large enough to be dispersed, but they settle out over time  Can be _______________, can scatter __________ filtered light

A heterogeneous mixture that separates into layers after time. Need to be stirred or shaken. Ex. Italian dressing, snow globe, muddy water

 What is a colloid? ◦ A colloid is a mixture in which the particles are dispersed throughout but are not heavy enough to settle out  ___________ be filtered, _______ scatter light Cannot can

- Form a homogeneous mixture. ◦ Ex. Milk, mayo, gelatin, whipped cream, stick of deodorant

Mixture Type Solute particle size Can it be filtered? Does it scatter light? SolutionSmall SuspensionMedium ColloidLarge No Yes No Yes

 Section Review ◦ Please answer the objectives on your summary sheet 1.Describe three properties of mixtures 2.Describe methods of separating the parts of a mixture 3.Analyze a solution in terms of its solute and solvent 4.Describe factors that affect solubility for solids, liquids, and gases 5.Explain how concentration affects a solution 6.Describe the particles in a solution, suspension, and colloid 7.Explain the difference between colloids, solutions, and suspensions  Section Review ◦ Please answer the objectives on your summary sheet 1.Describe three properties of mixtures 2.Describe methods of separating the parts of a mixture 3.Analyze a solution in terms of its solute and solvent 4.Describe factors that affect solubility for solids, liquids, and gases 5.Explain how concentration affects a solution 6.Describe the particles in a solution, suspension, and colloid 7.Explain the difference between colloids, solutions, and suspensions