Don’t forget to return your Lab Safety Contracts signed by yourself and a parent or guardian as soon as possible.

Chemistry

The study of matter, its

properties, and the changes it undergoes.

Branches of Chemistry•Organic•Inorganic•Analytical•Physical•Biochemisty•Nuclear

The Scientific Method

•a systematic method of finding the answer to a question or a problem

•not just used by scientists

1. State the problem

•lends direction to the problem solving

•provides a way to tell if the problem has been solved

2. Conduct Research

•gather as much information as possible beforehand

•what is already known?

3. Form a Hypothesis

•Make an “educated guess” as to the what or why of the problem

4. Conduct an Experiment

•test the hypothesis•one or more conditions should be controlled–held the same in all tests

•only test one variable at a time

•The condition to be deliberately changed from one trial to another is called the “independent variable”

•The “dependent variable” changes because of the change to the independent variable

5. Analyze the results

•look at the data or observations collected during the experiment

6. Make a conclusion

•does the data fit the hypothesis?–yes? hypothesis was correct

–no? modify the hypothesis and retest

Observations•What, not Why•Simply a record of what was observed

Conclusions•Why, not What•A statement of the cause behind the event

Theory•an explanation of how or why that has been successfully tested

•can never be proven, are accepted as true

•provide predictive powers

Law•a summary of the results of many observations or experiments

•describes what, doesn’t explain how or why

•often math equations

Lab Report•a summary of the results of your observations or experiments

•May be formal or informal

Informal Lab Report

•The exact requirements vary from lab to lab

•Often, a simple tabulation of your results with your calculations

•Must be neat and orderly

Formal Lab Report•More complete, with

expected sequence of text•Third person•All calculations shown•Data represented in table

form, as well as graphs or diagrams when appropriate

Formal Lab Report•Purpose/hypothesis•Materials•Procedure•Results

–Observations, data, calculations

•Conclusion

Chemistry

The study of matter, its

properties, and the changes it undergoes.

matter•Anything that has mass and

takes up space•Three types•Pure substances (aka “chemicals)

–Elements–Compounds

•Mixtures

properties•The characteristics that describe or help identify a substance

•Can be chemical or physical

Chemical properties•Describe how a substance reacts chemically

•Examples: –Combustibility–Rusting (oxidation)–Reaction with an acid

Chemical properties•Key idea:•Chemical properties can only be observed by changing the substance into a new, different substance

Physical properties•Describe the appearance of a substance

•Can be observed without changing the substance into a new, different substance

Physical properties - examples

•Color•Odor•Size•Mass•Weight•density

•Melting point•Boiling point•Physical

state–Solid–Liquid–Gas

•solubility

•Intensive physical propertiesDo not depend on the sample sizeexamples: temperature, density,

color, solubility, physical state, melting/boiling point

•Extensive physical propertiesare sample size dependentexamples: mass, volume, size

Chemistry is the study of…•Matter, its properties, and the

•Changes it undergoes•There are two types of changes–Chemical–physical

Chemical changes•Result in the formation of

new substances•Examples

–Elements compounds–Burning, oxidation, acid reactions

•Usually called “chemical reactions”

Chemical changes Indicators• Changes in color• Changes in odor• New physical state formed (not just

melting or freezing)– New solid – precipitation– Bubbles – new gas being evolved

• Change in temperature without using outside mechanism (burner, freezer)

Reaction Notation•Reactants Products•physical state often indicated- (s) = solid- (l) = liquid- (g) = gas- (aq) = aqueous - dissolved in

water

Physical changes•Do not result in the formation of a new, different substance

•Changes of physical state are physical changes

•Example: paper changes

Chemistry

The study of matter, its

properties, and the changes it undergoes.

elements•Matter that cannot be broken down into simpler substances by ordinary chemical means

•Example – “Lego” blocks

elements

•There are ~112 known •There are 92 naturally occurring •All have unique name and symbol

–1 letter = capitol–2 letters = cap w/ lower case–ex: B, C, Ca, Na

Some element names and symbols do not match - Latin names

• Na = sodium• Latin: natrium• K = potassium• Latin: kalium• Au = gold• Latin: aurum

• Ag = silver• Latin: argentum• Hg = mercury• Latin: hydrargentum

• Fe = iron• Latin: ferrum

Some element names and symbols do not match - Latin names

• Pb = lead• Latin: plumbum• Sn = tin• Latin: stannum• Cu = copper• Latin: cuprum

• Sb = antimony

• other: stibnium

• W = tungsten• Swedish:

wolfram

compound•A substance made of two or more elements chemically combined

•The properties of a compound are different than the properties of the elements that make up the compound

mixtures•Elements and compounds

(chemicals) blended together, but not chemically combined

•The chemical properties of the substances do not change

•No new chemicals are produced

Types of mixtures•Determined by how well the substances are mixed together

•Homogeneous mixtures–Uniform throughout

•Heterogeneous mixtures–Non-uniform

Separation of matter•How would you separate a

mixture of sand, salt, and water?

•Filter out sand•Boil off water, condense

vapors back to liquid state

Types of separation of mixtures• Filtration

– based on differences in solubility• Distillation

– Based on differences in boiling points• Crystallization

– Separate pure solids out of a solution• Chromatography

– Based in differences in flow rate through special papers or substances

Matter flowchart

Matter

Mixtures Pure Substances

Heterogeneous Homogeneous Compounds Elements

energy

•The ability to do work

•Work = Force x distance in the direction of the force

Forms of energy•Nuclear•Electrical•Solar (light)•Chemical•Heat•mechanical

Types of energy•Potential

–Due to position or composition

–Ex: chemical•Kinetic

–Due to motion–Ex: heat

What is the connection?

•E = mc2

•E = energy•m = mass

Chemistry

-the study of matter, its properties, and the

changes it undergoes.

Science is a

Process• Science is more a way of doing

things or solving problems than a collection of equations or ideas.

• There is no need to rediscover the wheel, so discoveries are recorded to the known body of knowledge.

•Pure Science –is concerned with making discoveries

•Applied Science–uses the discoveries to make new products or procedures