Properties

Physical property:

Can be observed without changing the identity (formula) of a substance

Chemical Property:

Can ONLY be observed when the identity (formula) of a substance is changed

Changes

Physical Change: Can be observed without changing the identity (formula) of a substance

Chemical Change:Can ONLY be observed when the

identity (formula) of a substance is changed

Involves a chemical reaction

Examples of Properties• Physical Chemical

Chemical change is a chemical reaction

Reactants: Starting substances

Products: Final (new) substances

Reactants → Products

Physical or Chemical Property?

• Iron Rusts

• Iron Melts (at high temperature)

• Sugar dissolves in water

• Alka-Seltzer fizzes when you add it to water

Physical Separation Methods

• Distillation: – Separates substances by differences in their boiling

points (usually liquids)

• Filtration:– Separates solid from liquid

• Chromatography: – Separates substances by differences in how they are

absorbed by a stationary phase and a mobile phase. (Ex: liquid mobile phase and paper stationary phase)

Physical Separation Techniques

Each method separates on the basis of a physical property

Distillation

Sorting

Filtration

Evaporation

Separation of a Mixture

How would you separate a mixture of

Salt and Sand

into its separate components?

What do you need to know?

Properties of saltWhite solidDoes not melt (until it reaches HIGH temp)Dissolves in water

Properties of sandSolid (color varies)Does not meltDoes not dissolve in water

Difference in properties

Salt dissolves in water

Sand does not

Possible Method

Add mixture to waterDissolve saltFilter out sand

Salt left in waterEvaporate off water

Mixture 2:

Salt, sand and iron filings

How would you separate this mixture into its separate components?

Physical Properties—Changes of State

Heat must be added

Melting Solid to Liquid

Evaporation or

Vaporization

Liquid to Gas

Sublimation Solid to Gas directly—

Skip Liquid state

Physical Properties—Changes of State

Heat must be removed

Freezing or Fusion

Liquid to Solid

Condensation Gas to Liquid

Deposition Gas to Solid directly—

Skip Liquid state

Energy

Energy is ability to do work (cause change)

Potential energy—stored energy

(Boulder on top of hill)

Kinetic energy—energy in use (motion)

(Boulder rolling down hill)

Forms of energyElectrical

Mechanical

Chemical

Heat

Light

Intensive Properties:

Independent of amount of substance

boiling point, density, color

Extensive properties:

Depend on amount of substance

mass, volume

Can We Explain and Predict Physical and Chemical Properties

of Matter?

Properties are related to the structure of matter

Need to examine pure substances in order to determine what the properties of a substance are

Element

Cannot be broken down into simplersubstances by chemical means.

Contains only one kind of atom

Smallest unit is atom

Represented by atomic symbol (one or two letters)

http://www.privatehand.com/flash/elements.html

Approximately 116 elements known

Most are solids. Some are gases. Only two (Br and Hg) are liquids.

Most elements are metals (are shiny, conduct electricity)

A few elements are nonmetals (including the gaseous elements)

• Seven gaseous elements exist as diatomic molecules (two atoms)

H2 O2 N2 F2 Cl2 Br2 I2

The subscript “2” indicates that there are two atoms of the element

Compounds

Can be broken down into simpler substances (elements) by chemical means

Contains two or more kinds of atoms (elements) combined in definite ratio

Atoms are held together by bonds between atoms

Smallest unit is molecule

Represented by formula

Chemical Formula

Chemical formula uses atomic symbols to show what elements and how many atoms of each element are in the compound

The number of each type of atom is shown by using a subscript after the symbol

If there is no subscript, we assume it is “1”

Examples

H2O 2 H atoms 1 O atom

CO 1 C atom 1 O atom

CO2 1 C atom 2 O atoms

Extra O makes a big difference

CO kills quickly. CO2 made by body.

Types of formulas

Molecular Formula gives the number and type of atoms in molecule

Structural Formula gives number and type of atoms in molecule AND shows how they are connected

Molecular NH3

Structural H ─ N ─ H

׀ H

Lines show “bonds” between atoms

Language of Chemistry

Alphabet: Atomic Symbols

Words: Formulas

Sentences: Chemical Equations

Chemical Equations

Reactants → Products

CO + O2 → CO2

Law of Conservation of Mass (Matter)

Cannot create or destroy matter by chemical means

Must “balance” equation so that there are the same number of atoms of each kind on both sides of the equation

2 CO + O2 → 2 CO2

RULE: Cannot change the formula of substance---can only change the number of molecules

Coefficients

The numbers in front of a formula show the number of molecules of the substance

2 CO + O2 → 2 CO2

2 CO = 2 molecules of CO

Practice Balancing Equations

• AgNO3 + HCl AgCl + HNO3

• HCl + O2 H2O + Cl2

• Ba(OH)2 + HCl BaCl2 + H2O

Practice Balancing Equations

• AgNO3 + HCl AgCl + HNO3

• HCl + O2 H2O + Cl2

• Ba(OH)2 + HCl BaCl2 + H2O