What is Chemistry?

• Chemistry – the study of the composition of matter and the changes that matter undergoes

• Matter – the ‘stuff’ that things are made of– Everything is made of matter– Examples of things containing matter:

Divisions of Chemistry

• Practical – applications to everyday life– Example: teflon, computer chips

• Theoretical – Does not apply to everyday life (at least not yet)

– Example: force fields, light speed travel

Divisions of Chemistry

• 5 major areas of study:– Organic – study of carbon containing substances– Inorganic – substances without carbon– Analytical – composition of substances– Physical – behavior of chemicals– Biochemistry – chemistry of living organisms• These areas overlap

Why Study Chemistry?

• Come up with an aspect of life that does not involve chemistry:

How do these pictures relate to chemistry?

The Scientific Method

• A logical approach to the solution of scientific problems

• Closely related to common sense:– Example: When you turn on a flashlight and it

does not light – you made an observation– You guess that the batteries are dead – this is a

hypothesis– You put new batteries in the flashlight –

experiment

The Scientific Method• Observation – Observe something about the

world around you• Hypothesis – propose an explanation for what

you observed• Experiment – Test your hypothesis with a

controlled experiment• Collect and Analyze data – look for a

correlation between data and hypothesis• Theory – accepted explanation of why the

experiment gave the results it did

Scientific Law

• Statement summarizing results of many observations and experiments

• Describes a natural phenomenon without attempting to explain it.– Example: Law of Gravity: no accepted explanation

exists, we just know it happens

How is a scientific theory different than a scientific law?

Do scientists always follow the scientific method?

Give an example of when a scientist cannot use the scientific method:

Matter

• Matter is anything that occupies space and has mass.

• Mass – tha amount of matter in an object (measured in grams)

• Volume – the amount of space an object occupies (mL or L or cm3)

• Weight – the amount of pull of gravity on an object (measured in Newtons)

States of Matter Solid (s)

1. Definite shape and definite volume 2. Particles stick rigidly together and vibrate – they don’t

move position 3. Often crystalline structure – fixed, repeating internal

structure4. Amorphous solids – do NOT have a crystalline structure 5. Melting point – temperature at which a solid turns into

a liquid (solid and liquid are in equilibrium

6. Sublimation – change from a solid to a gas ( skips the liquid stage

States of Matter Liquid (l)

1. No definite shape but has definite volume2. Particles stick together but NOT rigidly and do NOT have a pattern. (more random)3. Evaporation – when liquid changes into a gas 4. Vapor pressure – in closed containers some liquid changes to a gas which exerts pressure on the container walls

a. Table H in reference tables.

States of Matter

5. Boiling Point – when vapor pressure equals atmospheric pressure

A. the atmospheric exerts a pressure on everythingB. at the boiling point of water the vapor

pressure is 101.3Kpa,(1atm.) and is equal to the atmospheric pressure

States of Matter

Gas (g)1. No fixed volume and no definite shape2. Gas pressure is caused by particles move and collide with the walls of a container3. Particles are far apart and move in all directions4. Can be compressed or expanded

Aqueous (aq) Something dissolved in water, example NaCl(aq)

States of Matter

Plasma 1. Composed of electrically charged atomic particles 2. Examples: Stars including the our Sun 3. Made by heating gas to extremely high temperatures or or by passing a current though it

States of Matter

Entropy 1. As matter goes from a solid to a

liquid and then a gas the entropy increases

Note: Entropy is the randomness of a particle's energy and position

Physical Properties

Properties - characteristics that identify an object:

Physical properties: observed and measured without changing to something else

Ex: State, Color, solubility and melting point

Physical Change: Alters 1 or more physical properties without changing the chemical composition

Chemical Properties

Chemical Properties: formed when a substance reacts with another substance to form a different chemical composition

Chemical Changes: cannot be observed without altering the chemical composition

Ex: Na + Cl NaCl (Sodium Metal) + (Chlorine gas ) produces(Table Salt)

Poisonous

Elements

The basic building blocks of matter:Elements are pure substance that can NOT be broken into simpler substances. Found on the Periodic Table.

Ex: C, N, O…

Each element has their own unique physical and chemical properties

CompoundsCompounds can be broken down into

single elements by chemical changesEx: H20 into 2 Hydrogens and 1 Oxygen NaCl into Sodium and Chlorine

Binary compounds have only two elements.Ternary – compounds that have 2+ elementsDiatomic compounds have only two elements that are the same.

Diatomic elements include – H, N, O, F, Cl, Br and I

Pure Substances and Mixtures

Pure substances1. Matter with fixed composition (can be elements or

compounds)

2. Cannot be separated into any other form of matter by physical change (for compounds)

Ex: He is an element (look on the Periodic Table) O2 (g) is a diatomic gas, Oxygen

NaCl is table salt

Pure Substances and Mixtures

Mixtures 1. Combined 2 or more pure substances

Ex: salt and sugar2. Composition can vary3. Can separate by physical means4. Can be heterogeneous OR

homogeneous

Classification of Matter

Homogenous matter1. Same parts with same properties

throughout

Ex: Teaspoon of sugar, any element

Classification of Matter

Homogeneous mixture1. Uniform blend of 2 or more substances2. Can vary in proportion (like concentration)

3. Every part is exactly like every otherpart (think Kool-Aid)

Ex: salt dissolved in water (a solution)

Classification of Matter

Heterogeneous matter1. Different parts with different properties

Ex: Salt and Pepper

Classification of MatterHeterogeneous mixture

1. Different parts with different properties2. Made of 2 or more substances with each retaining their unique properties (boiling point, solubility, etc.)

3. NOT the same composition or properties throughout4. Composition can vary5. Does NOT make a solution

Ex: Salt and sand

Separating Mixtures

A. With a magnet1. Mixture of iron and sulfur2. Separated by their physical

propertiesB. Distillation

1. Process in which a mixture can be separated by its boiling points

2. Ex: Petroleum (mixture of gas, kerosene and oil) when it boils the liquids separate with gas boiling first

Separating Mixtures

C. Filtration 1. Process that separates the solid and liquid parts 2. Use filter paper, funnel – the liquid part goes through the filter

a. If solid is dissolved in liquid it will also go through paper

Ex: Soda has carbon dioxide gas

Separating Mixtures

D. Chromatography1. Way to separate different molecules in a mixture 2. Put drop from mixture near one end of chromatography paper – then put paper into the solvent and the mixture will move up so that molecules move different distances

http://www.wooster.edu/chemistry/analytical/gc/default.html