Ch. 4 – Elements, Compounds, and Mixtures

II. Composition of Matter

(p. 80 – 98)Matter Flowchart

Pure Substances

Mixtures

MATTER

A. Matter Flowchart

MATTER

Can it be separated by physical means?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be decomposed by chemical means?

noyesIs the composition uniform?

noyes

B. Pure Substances

Element matter composed of identical atoms EX: copper

Elements:

Element: A pure substance that cannot be separated into simpler substances by physical or chemical means.

Pure substance: a substance in which there is only one type of particle (atom). (there is only one type of particle in it)

Every particle in a 5g nugget of gold is like every other particle of gold.

Every element has Characteristic Properties:

Characteristic Properties do not depend on the amount of material present.

Physical Properties: Boiling pt., melting pt., density, color, hardness, texture

Chemical Properties: reactivity, flamability

How do you identify an element?

Look on a periodic table (see your agenda on page 117)

Use the physical properties: color, hardness, texture, etc.

Use chemical properties: reactivity, flammability/combustibility

Elements are divided into 3 categories:

Elements

Metals Nonmetals Metalloids

Examples of Elements

B. Pure Substances

Compound matter composed of 2 or

more elements in a fixed ratio that have been chemically combined

properties differ from those of individual elements

EX: salt (NaCl)

Examples of Compounds

Marriage

Divorce

Forming of a bond is like marriage

•More stable

•exothermic

The breaking of a bond relates to a

divorce.

•Less stable

•Endothermic

Bonds

Bonds Between Atoms

Covalent

Ionic

Polyatomic Ions

Metallic

Ionic Bonds

•What is an Ionic Bond?- An Ionic Bond is a chemical bond resulting from the TRANSFER of electrons from one bonding atom to another

• When is an ionic bond formed?- An ionic bond is formed when a cation (positive ion) transfers electrons to an anion (negative ion).

Covalent Bonds•What is an Covalent Bond?

- A covalent bond is a chemical bond resulting from SHARING of electrons between 2 bonding atoms.

• What forms a covalent bond?- A covalent bond is formed between two nonmetals.

Metallic Bonding

What is a Metallic Bond?

- A metallic bond occurs in metals. A metal consists of positive ions surrounded by a “sea” of mobile electrons.

Name 4 Characteristics of a Metallic Bond.

1. Good conductors of heat and electricity

2. Great strength

3. Malleable and Ductile

4. LusterThis shows what a metallic bond might look like.

Polyatomic Bonds

What is a Polyatomic Bond?

- A polyatomic bond is charged group of covalently bonded atoms. It is made up of more than one atom.

Polyatomic ions usually have a charge because the collection of atoms has either gained an extra electron or else it has lost an electron.

Anion- negative ion Cation-positive ion Octet Rule- rule that states that atoms tend to

gain, lose, or share electrons so that each atom has full outermost energy level which is typically 8 electrons.

Polyatomic Ion- charged group of covalently bound atoms

Monatomic Ion- ion formed from a single atom Molecule-neutral group of atoms united by

covalent bonds

II. Balancing Equations

A. Balancing Steps1. Write the unbalanced equation.

2. Count atoms on each side.

3. Add coefficients to make #s equal.

Coefficient subscript = # atoms

4. Reduce coefficients to lowest possible ratio, if necessary.

5. Double check atom balance!!!

1 1

1 1

2 3

2 2

3

6 6

3

2 3 3 2 3 2 Al + CuCl2 Cu + AlCl3

Al

Cu

Cl

2 3 2

B. Balancing ExampleAluminum and copper(II) chloride form

copper and aluminum chloride.

Practice Balancing Equations

1. H2 + O2 ---> H2O

2. N2 + H2 ---> NH3

3. S8 + O2 ---> SO3

4. N2 + O2 ---> N2O

5. HgO ---> Hg + O2

C. Balanicing Equestions

Phases are often shown as: (s) solid, (l) for liquid, and (g) gas. Compounds that dissolved in water are designated as (aq) for aqueous.

C(s) + O2 (g) CO2 (g)

Mixtures

2 or more substances mixed together but not chemically combined

Properties of Mixtures

Each substance keeps it original properties.

Some physical properties may change appearance but the chemical properties stay the same.

The amounts of substances can change. They do not have to stay the same.

Mixtures can be separated easily through physical means.

Separation of Mixtures

Distillation: separates mixtures based on boiling points

Magnetism: separates mixtures by attracting the iron

Centrifuge: separates mixtures according to densities

Filtration: separate a solid from a liquid

Examples of Separation

C. Types of Mixtures

Homogeneous Mixture (Solution) even distribution of components very small particles particles never settle EX: saline solution

C. Mixtures

Heterogeneous Mixture uneven distribution of components colloids and suspensions EX: granite

C. Mixtures

Colloid medium-sized particles Tyndall effect - particles

scatter light (looks cloudy) particles never settle EX: milk

C. Mixtures

Suspension large particles particles scatter light particles will settle

(needs to be shaken) EX: fresh-squeezed

lemonade

Solutions: This is a type of homogeneous mixture but the particles do dissolve.

Solute: the substance that is dissolvedSolvent: the substance that does the dissolving (universal solvent: water)Solution: the final productSolubility: If the substance dissolves then it is soluble. If the substance does not dissolve it is insoluble.Alloys: This is a solid solution. Metals are a good example of alloys.

Examples of Mixtures