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