Elements, Compounds, and Mixtures

Chapter 4Material on Midterm

What colors make up black ink?

Mystery Mixture

Objectives◦Describe pure substances◦Describe the characteristics of elements, and give examples

◦Explain how elements can be identified

◦Classify elements according to their properties

Section 1: Elements

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 ___________

Section 1: Elements

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

Section 1: Elements

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

Elements

Cobalt Iron Nickel

Melting Point: 1495 C

Melting Point: 1535 C

Melting Point: 1455 C

Density: 8.9 g/cm3 Density: 7.9 g/cm3 Density: 8.9 g/cm3

Conducts electric current and heat

energy

Conducts electric current and heat

energy

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

Section 1: Elements

Classifying ElementsExample: 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

Section 1: Elements

Metals

Nonmetals

Metalloids

Section 1: Elements

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

Section 1: Elements

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

Section 2: Compounds

What are compounds?◦A compound is a pure substance

composed of two or more elements that are ______________ combined

As a result of a ______________

Section 2: Compounds

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.

Compounds

Compound Elements Combined

_________________Sodium and Chlorine

__________Hydrogen and Oxygen

Vinegar Hydrogen, Carbon, and Oxygen

_____________________Carbon and Oxygen

Baking soda Sodium, Hydrogen, Carbon, and Oxygen

Section 2: Compounds

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? _________________!

Section 2: Compounds

SAME

H2O

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?

Section 2: Compounds

OWN

Properties Compounds versus Elements◦A compound will have different

______________ than the elements that make it up

Section 2: Compounds

properties

Compounds

Sodium Soft Silvery, white metal Reacts violently

with

Chlorine Gas Poisonous Greenish-yellow

But when chemically combined…

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

Section 2: Compounds

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

How to break down a compound

Section Review◦Please answer the objectives on your

summary sheet1. 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

Section 2: 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

Section 3: Mixtures

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

Section 3: Mixtures

not chemically combined

identity

2 Categories of Mixtures

Heterogeneous Mixture

Homogeneous 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

Section 3: Mixtures

physical

Section 3: Mixtures

Separating a mixture

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.

Separating a mixture 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

Section 3: Mixtures

not

Comparing Mixtures and Compounds

Section 3: Mixtures

MIXTURES COMPOUNDS

Made up of elements, compounds, or ________

Made of _____________

_________________ in original properties of components

_____________ in original properties of components

Separated by ___________means

Separated by ___________ means

Formed using ____ ratio of components

Formed using a _____ ratio of components

elementsboth

No change

Change

physicalchemical

any set

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

Section 3: Mixtures

Cannot

solute

solvent

Section 3: Mixtures

Hide the LOOT in the

VENT!

Solutions form when the solute dissolves in the solvent

◦If it ________ dissolve, its soluble

◦If it _____________ dissolve, it is insoluble

Section 3: Mixtures

does

doesn’t

Solute State Solvent State Examples

Gas Gas Dry air (oxygen in nitrogen)

Gas Liquid Soda (carbon dioxide in water)

Liquid Liquid Antifreeze (alcohol in water)

Solid Liquid Salt water (salt in water)

Solid Solid Brass (zinc in copper)

Section 3: Mixtures

Concentration of Solutions◦The concentration is a measure of the

__________ of solute in a solvent Units: g/mL

◦Lots of solute __________________◦Little solute _______________

Section 3: Mixtures

amount

concentrateddilute

What is solubility?◦ The solubility is the ability of a solute to

____________ in a solvent at a certain temperature

Section 3: Mixtures

dissolve

0 20 40 60 80 1000

40

80

120

160

200

240

Solubility of Different Solids in Water

Cerium sulfateSodium chloridePotassium bromideSodium nitrateSodium chlorate

Temperature (°C)

So

lub

ilit

y (

g/1

00

ml

of

wa

ter)

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

Section 3: Mixtures

less

more

◦ To get solids to dissolve faster…Section 3: Mixtures

___________________________

- Causes particles to separate and spread out faster

_____________

- Causes particles to move more quickly and separate

________________

- Spreads out solute to mix with solvent more quickly

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 timeCan be _______________, can scatter __________

Section 3: Mixtures

filteredlight

A heterogeneous mixture that separates into layers after time.Need to be stirred

or shaken.Ex. Italian dressing,

snow globe, muddy water

Suspension

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

Section 3: Mixtures

Cannot

can

- Form a homogeneous mixture.

◦Ex. Milk, mayo, gelatin, whipped cream, stick of deodorant

Colloid

Mixture Type

Solute particle

size

Can it be

filtered?

Does it scatter light?

Solution Small

Suspension Medium

Colloid Large

No YesNo

No YesYes

Section Review◦ Please answer the objectives on your summary

sheet

1. Describe three properties of mixtures2. Describe methods of separating the parts of a

mixture3. Analyze a solution in terms of its solute and solvent4. Describe factors that affect solubility for solids,

liquids, and gases5. Explain how concentration affects a solution6. Describe the particles in a solution, suspension,

and colloid7. Explain the difference between colloids, solutions,

and suspensions

Section 3: Mixtures