Chemistry• A physical science

that involves the study of the properties, composition,& structure of matter and the changes it undergoes.

What is a chemical?

• Any substance that has a definite composition or is used or produced in a chemical process.

• Sugar is an example of a chemical

• Everything that has mass and volume is called matter

• Can be simple as in elements on the Periodic Table

• or complex molecules as atoms combineElements in the same vertical

row will behave similar in chemical reactions

Three Major Classes of Elements

• Metals- located on the left of the Periodic Table- most of the elements

• Non-Metals- located on the right of the Periodic Table

• Metalloids- on the zigzag line between Metals and Nonmetals- have properties that are skewed- ie…Silicon is conductive

• You will have to memorize the symbol and element name for approximately 40 common elements

Properties of MetalsProperties of Metals Metals are good conductors of heat and electricity

Metals are malleable (can be shaped)

Metals are ductile (can be drawn into wires)

Metals have high tensile strength

Metals have luster (shiny)

PropertiesProperties of Nonmetalsof Nonmetals

Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element. Nonmetals are poor conductors of heat and Electricity

Nonmetals tend to be brittle

Many nonmetals are gases at room temperature

Atoms Unite To Form Compounds

• Chemical Formula indicates number and type of atoms within the molecule The formula to the left is the molecule for indigo:

C16H10 N2O2.

What type of atoms and how many are there in one molecule?

What is not matter?

• Light

• Electricity

• Sound

• Fixed composition

• Cannot be separated into simpler substances by

physical methods (physical changes)

• Can only be changed in identity and properties by

chemical methods

• Properties do not vary- Unique Density, Constant

Boiling and Melting Points

Compounds

• Chemically joined elements- Can be decomposed into simpler substances by chemical changes, always in a definite ratio

Elements • Cannot be

decomposed into simpler substances by chemical changes

• Variable composition• Components retain their characteristic properties• May be separated into pure substances by physical

methods sifting, evaporation, magnetism, etc…• Mixtures of different compositions may have

widely different properties• Do NOT have definite boiling/melting points

Homogenous mixtures look the same throughout but can be separated by physical means

Examples: salt water, soda

• Have the same composition throughout

• Components are indistinguishable

• Can exist between all phases of matter: air (gases) brass (alloy- blend of multiple metals -solids)

soda (gas, solid, liquid)

Adding Liquids Together

• Miscible- will mix- water and alcohol

• Immiscible- wont mix

water and oil

Solutions are homogenous mixtures that do not scatter light. These mixtures are created when something is completely dissolved in pure water. Therefore, they are easily separated by distillation or evaporation. Appear in one phase of matter

Examples: sugar water, salt water

Parts of a solution

• Solvent- part that does the dissolving- water is our universal solvent

• Solute- part that was dissolved (salt)

How do we increase solubility of a solid into a liquid

• Heat it- more collisions between solute and solvent

• Mix- Fresh solvent to solute

• Crush- more surface area- more contact

Increase solubility of a gas in a liquid• Henrys Law- solubility of the

gasis directly proportional to the pressure above the liquid-

• Effervescence- rapid escape of gas from liquid

• Decrease temperature- slows down diffusion

Heterogeneous mixtures are composed of large pieces that are easily separated by physical means (ie. density, polarity, metallic properties, size).

Pond Water, Vegetable Soup- Suspensions Visible particles

Starch Water: invisible to the eye :colloid

Colloids are Tricky• Some heterogeneous

mixtures appear as solutions to the eye:

• Blood, Milk, starch water

• Need a test: Tyndall Effect a light will scatter the suspended particles

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

noyes

Colloids Suspensions

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Physical Properties – Observable traits of a material that may be measured

without altering the substance

Examples: Mass, Color, Melting Point, Boiling Point, Density

We can use physical properties to separate mixtures:

Please determine a method to separate the following and determine the type of matter:

Oil and Water

Iron and Sand

Sand and Salt

Sulfur and Sugar

What are the physical properties of the substance to

the right?

What do you think the material is that made this bracelet?

How could you be sure?

Density- the amount of material in a given volume- unique to the material

Chemical Change- an irreversible change

that changes the identity and make up

of the materialExamples:

RustingBurning

• There is no observable change in the quantity of matter during a chemical reaction or a physical change.

In other words, matter cannot be created nor destroyed. It is just converted from one form to another

Energy comes in two forms :

Kinetic Energy: Movement

Potential Energy: Stored

All matter, regardless of state, undergoes physical and chemical changes. These

changes can be microscopic or macroscopic.

A physical change occurs when the substance changes state but does not change its chemical composition. It is not permanent and is reversible! Example Phase Changes!

                                      

Physical Change

For example: Ice melting to water. The form or appearance has changed, but the properties of that substance are the same (i.e. it has the same melting point, boiling point, chemical composition, etc.)

• Melting point• Boiling point• Vapor pressure• Color• State of matter• Specific Heat

• Density • Electrical conductivity• Solubility• Adsorption to a

surface• Hardness

Names of Water Phase ChangesEndothermic Requires

Energy to go forward• Melting: Solid Liq

• Boiling (forced)

Liquid Gas• Evaporation ( spon)

Liquid Gas• Sublimation

Solid Gas

Exothermic Gives energy off

• Condensation

Gas Liq• Freezing:

Liq Solid• Deposition:

Gas Solid

A substance changes into something new. It is irreversible.

Indications of A Chemical Reaction• Bubbles- gas given off

• Change in energy- becomes warm- exothermic

becomes cool- endothermic

light is given off

• A precipitate (solid) forms

• Sometimes a change in color-

All Chemical Changes can be written as a reaction

• A + B AB

• A, B are the starting materials- reactants

• AB is the result- product

• Reaction with acids• Reaction with bases

(alkalis)• Reaction with oxygen

(combustion)• Ability to act as

oxidizing agent

• Ability to act as reducing agent

• Reaction with other elements

• Decomposition into simpler substances

• Corrosion

• Physical and chemical properties may be intensive or extensive.

• Intensive properties such as density, color, and boiling point do not depend on the size of the sample of matter and can be used to identify substances.

•

• Extensive properties such as mass and volume do depend on the quantity of the sample.

• Physical properties are those that we can determine without changing the identity of the substance we are studying.

• The physical properties of sodium metal can be observed or measured. It is a soft, lustrous, silver-colored metal with a relatively low melting point and low density.

• Hardness, color, melting point and density are all physical properties.

Specific Heat• Physical Property that is unique

to the material

• Amount of energy required to heat 1 gram of a substance by 1 degree Celsius

• -Why do you choose to sit on the wooden bleachers on a cold fall day for a football game instead of the metal bleachers?

• Chemical properties describe the way a substance can change or react to form other substances.

• These properties, then, must be determined using a process that changes the identity of the substance of interest.

• One of the chemical properties of alkali metals such as sodium and potassium is that they react with water. To determine this, we would have to combine an alkali metal with water and observe what happens.

• In other words, we have to define chemical properties of a substance by the chemical changes it undergoes.

& The Kinetic Molecular Theory •All matter is made of atom and molecules that act as tiny particles•These particles are always in motion (yes even in solids)

•The higher the temperature the faster the particles move- •Kinetic energy is directly proportional to Kelvin Temperature ( bigger particles move slower)

Three PhasesThree Phases

•Have a definite shape•Have a definite volume

Molecules are held close together and there is very little movement between them. Vibrational

Kinetic Molecular Theory

•Have an indefinite shape•Have a definite volume

Kinetic Molecular Theory:Atoms and molecules have more space between them than a solid does, but less than a gas (ie. It is more “fluid”.) Has 2 dimensional motion- can slide past each other

•Have an indefinite shape•Have an indefinite volume

Kinetic Molecular Theory:

Molecules are moving in random patterns with varying amounts of distance between the particles.

At 100°C, water becomes water vapor, a gas. Molecules can move randomly over large distances.

Below 0°C, water solidifies to become ice. In the solid state, water molecules are held together in a rigid structure.

Between 0°C and 100 °C, water is a liquid. In the liquid state, water molecules are close together, but can move about freely.

Changing states requires energy in either the form of heat. Changing states may also be due to the change in pressure in a system.

Heat of formation, Hf. Heat of vaporization, Hv

Plasma is by far the most common form of matter in the universe (not here on Earth). Plasma in the stars and in the tenuous space between them makes up over 99% of the visible universe and perhaps most of that which is not visible. Fluorescent Light Bulbs…

(Above)

X-ray view of Sun from Yohkoh, ISAS and NASA

Star formation in the Eagle Nebula

Space Telescope Science Institute

, NASA

(below)

Plasma radiation within the Princeton Tokamak during operation.

Laser plasma interaction during inertial confinement fusion test at the University of Rochester.

Plasma consists of a collection of free-moving electrons and ions - atoms that have lost electrons. Energy is needed to strip electrons from atoms to make plasma. The energy can be of various origins: thermal, electrical, or light (ultraviolet light or intense visible light from a laser). With insufficient sustaining power, plasmas recombine into neutral gas.

Products manufacturedusing plasmas impact our daily lives:

EXAMPLES:

•Computer chips and integrated circuits

•Computer hard drives

•Electronics

•Machine tools

•Medical implants and prosthetics

•Audio and video tapes

•Aircraft and automobile engine parts

•Printing on plastic food containers

•Energy-efficient window coatings

•High-efficiency window coatings

•Safe drinking water

•Voice and data communications components

•Anti-scratch and anti-glare coatings on eyeglasses and other optics