Unit 1 Notes

Dunton

Chem 111 Notes Chapter 1.1Why Study Chem? Chemistry: study of properties /

composition of matter and the changes they undergo

Can be applied to all aspects of life Impacts society (health care, food,

clothing, environmental issues, etc) Chemistry is the central science.

(incorporates biology, engineering, agriculture, geology, physics)

Branches of Chemistry (May Overlap) Organic Chemistry- w/carbon Inorganic Chemistry - w/o carbon Analytical Chemistry - composition & small

quantities of substances Physical Chemistry - describes the behavior of

chemicals Biochemistry Chemistry - study of chemistry of

living organisms Pure Chemistry- chemical aspects for

knowledge Applied Chemistry- uses knowledge to

solve real world problems

1.3 Scientific method- logical approach to

solution of scientific problems, guidelines for the practice of science Collect data (Observe , experiment)

Qualitative Measurement- descriptive non-numerical form “feels hot/cold” 

Quantitative Measurement- definite form- number & unit

Look for patterns and develop a hypothesis Hypothesis- proposed explanation for what is observed

Experiment- test hypothesis & refine it Conclusion- Draw a conclusion from the data

Lab Design Independent variable- what you change Dependent variable- what you measure Control- variables you keep the same Be able to define and identify these

variables When you record your data, you need a way

to organize it: Use tables, charts and graphs to organize

your data If you are using a graph, the dependent

variable goes on the y-axis and the independent variable goes on the x-axis

Theory- broad extensively tested explanation of WHY experiments give results

Ø      Never ProvenØ      Mental picture to predict behavior of natural systemsØ      “Why something happens”Ø      Theory of Natural SelectionØ      Big Bang Theory

Law- statement summarizes results of many experimentsØ      Describes phenomena w/o explaining itØ      “What happens” but never WHYØ      Law of Constant CompositionØ      Law of Conservation of Mass/Matter  

1.2 Matter Matter is classified by state (s, l,

g) or by composition (element, compound or mixtures).

**Cooperative group activity

Matter & Mass vs weight Matter- has mass & takes up

space Weight- force; measures pull on object

by gravity Mass- amount of matter compared to a

standard SI unit is kilogram Use balance NOT SCALE!! Measure of inertia

States of matter: Solids-

Definite shape & volume, Particles rigidly packed, Almost incompressible, Expand slightly when heated

Liquids- Definite Volume, Indefinite shape, Takes shape of container, Particles flow over each other (fluid), Almost incompressible, Expand slightly when heated One surface free to react

Gases- Takes shape & volume of container, Easily compressed, Expand when heated, Particles flow over each other ** Gases are gases at rm. temp **Vapor- s or l at rm T

Pure Substances- Element- simplest form of matter

Represented by symbols Diatomic Elements-usually gases, occur

in groups of 2 hydrogen (H2), oxygen (O2), nitrogen (N2), fluorine (F2), bromine (Br2),chlorine (Cl2), iodine (I2), astatine (At2)

Allotrope- one element occurring in different forms O2 (oxygen) & O3 (ozone) Carbon (diamond & graphite)

Compounds- elements chemically bonded Must be separated by chemical

means: heating & electrolysis Have specific ratios H2O Subscripts tell number of atoms,

no # means 1

Law of Definite Proportions: a compound is always composed of the same elements in the same proportion by mass Percent by mass = mass of element x 100

mass of compound Law of Multiple Proportions: when different

compounds are formed by the combination of the same elements, different masses of one element combine with the same relative mass of the other element in a ratio of small whole numbers

A 78 g sample of an unknown compound contains 12.4 g of hydrogen. What is % by mass of hydrogen?

Complete the following table and then analyze the data to determine if the compounds I and II are the same compound. If the compounds are different, use the law of multiple proportions to show the relationship between them.

Compound

Total g

g Fe g O % Fe % O

I 75.00 52.46 22.54

II 56.00 43.53 12.47

Mixture- blend of 2 or more pure substances % composition varies from sample to sample

Phase- part of a system w/uniform composition & properties

Heterogeneous- not uniform in composition More than 1 phase

Homogeneous- uniform composition 1 phase Also called solutions s, l, or g

Separate mixtures- Distillation- uses BP to separate

liquids Filter- uses size Magnetism- Chromatography – size & polarity Density- floatation Solubility- crystallization Reactivity MP

1.3 Physical property- can be

observed w/o changing composition Color, D, solubility, odor, hardness,

density, MP & BP Helps to ID substances Intensive properties are

independent of the amount present Extensive properties change as the

quantity changes

Physical Changes- Alters material w/o changing composition/identity; Cutting, grinding, phase change, bending ex: change of state

sg sublimation sl melting gl condensation lg vaporization (evaporation & boiling) ls freezing gs resublimation

Heating Curve:• Notice that there

is no change in temperature during a phase change.

• All extra energy in phase change is being used to break bonds

solid

liquid

gas

meltingfreezing

vaporizationcondensation

tem

pera

ture

time

Some phase changes gain or lose energy

Chemical Properties- ability to undergo a chemical reaction look for “ability to ______” You will usually need another chemical

to “undo” it Reactants (what you start with) –

(yields, produces) Products (what you end with)

Chemical change- 1 or more substances change into new substances Ex: Burn, rust, corrode, decompose, rot,

ferment, and explode, nuclear change (change # p or n in nucleus of atom)

Indicators of a chemical reaction: Energy change, Color change Odor change, Production of Gas Production of Precipitate (solid) Light Irreversibility

Nuclear change Concerns nucleus of atom Fission (splitting nucleus) or fusion

(combining nuclei) One element changes into another element

Energy - Ability to do work or produce heat PE - stored in bonds KE - E of motion (constant motion of

atoms or molecules T) Law of Conservation of Energy

- in any chemical rxn or physical process, E is converted to other forms – not created or destroyed.

Chemical Potential Energy - Stored energy in bonds – based on composition and type of atoms

During all chemical changes, overall mass is preserved The Law of Conservation of Mass: mass

is neither created nor destroyed. Massreactants = Massproducts

From a laboratory process designed to separate water into hydrogen and oxygen gas, a student collected 10.0 g of hydrogen and 79.4 g oxygen. How much water was originally involved in the process?

A 10.0 g sample of magnesium reacts with oxygen to form 16.6 g of magnesium oxide. How many grams of oxygen reacted?

Practice Chemical or Physical properties

oxidation density color conductivity Reactivity

Intensive or extensive properties malleability mass color radioactivity length

Matter (may be solid, Liquid, or gas) anything that occupies space and has mass.

Mixtures Pure Substances

Compounds: elements united in

fixed ratios

Elements: cannot be

subdivided by chemical or

physical change

Heterogeneous mixture:

Non-uniform composition

Homogeneous mixture: uniform

composition throughout

Physical Changes

ChemicalChanges