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 properties  Do not depend on the sample size  examples: temperature, density, color, solubility, physical state, melting/boiling point Extensive physical properties  are sample size dependent  examples: 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

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 = mc 2 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