Physics - St. Johns County School District

Physics - St. Johns County School District

Chemistry I Introduction, Review of Required Prerequisites, & Lab Safety What is Chemistry? Chemistry is the study of matter and the changes that it undergoes A basic understanding of chemistry is central to all sciences: biology, physics, Earth science, ecology, etc. Branches of chemistry include: Organic Chemistry

Inorganic Chemistry Physical Chemistry Analytical Chemistry Biochemistry Who cares! How much can I get paid for learning this stuff? More than a teacher!!! Scientific Research Chemist, Chemical Engineer, Consultant, Forensics, Food and Flavor Chemist, Geochemist, Medicine or even business/finance About 40-60k for starting pay with B.S. and M.S. and 100k-200k for medical field So Chemistry = Conversions = Math Problems go and buy a good calculator and stop stealing them from my

desk!!! SI Units Base Quantity Metric System Base Unit Symbol Length meter m Mass

kilogram kg Time second s Temperature Kelvin K Amount of Substance mole

mol Electric Current ampere A candela cd Luminous Scientific Method Do you know the steps to the scientific method? In order and completely?

Do you know the process of publishing, peer review, creating a theory? The difference between a theory and a scientific law? The Nature of Science

The Scientific Method : Observe Question Hypothesize Test hypothesis by observations and/or experimentation Collect data Draw a conclusion Modify hypothesis if necessary Test again Experiments must be able to be repeated by others.

Science is loosely described as the search for knowledge. It is observation, study, and experimentation to find out about the nature of things. Social or Natural including: Psychology Biology Sociology Physical Earth Observations Gathered through your

senses A scientist notices something in their natural world Observations An example of an observation might be noticing that many salamanders near a pond have curved,

not straight, tails Hypothesis A suggested solution to the problem. Must be testable Sometimes written as If Then statements Predicts

an Hypothesis An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil Experiment A procedure to test the hypothesis.

Experiment A good or valid experiment will only have ONE variable! Experiment Variable factor in the experiment that is being tested Controls and Variables

Scientific Experiments Follow Rules An experimenter changes one factor and observes or measures what happens. The Control Variable The experimenter makes a special effort to keep other factors constant so that they will not affect the outcome.

Those factors are called control variables. What is the Purpose of a Control? Controls are NOT being tested Controls are used for COMPARISON Other Variables The factor that is changed is known as the independent variable.

The factor that is measured or observed is called the dependent variable. Example of Controls & Variables For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since

you are only interested in finding a route that is fastest for you, you will do the walking yourself. What are the Variables in Your Experiment? Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.

One more thing it is best to make several trials with each independent variable. Valid Experiments Remember: To be a Valid Experiment: Two groups are required --- the control & experimental groups There should be only one variable

Data Results of the experiment There are two ways to describe or analyze your data: 1.Qualitative Data Tells about qualities of an object or thing. Smell, color, sound, etc. Think QUALITative, Quality. 2.Quantitative Data Tells about quantity, or numbers of data. 5 inches, 10 lbs, 12 minutes, etc. Think QUANTITative, Quantity.

Data Must be organized Can be organized into charts, tables, or graphs Data When analyzing data, you have to account for error in your work. Error is an expression

of the amount of imprecision in a set of measurements. Error is commonly expressed as percentage error. Example: Today, there is a 45% chance of rain, +/2%. *Organizing Data Line Graphs Bar Graphs Continuous Change Pie Charts Comparison of

similar things X-Axis = independent Happens anyway, like time Y-Axis = dependent it is a result of the test parts/portions/percents of a whole Which is Which??? Graphing The independent variable (the factor that is changed during an experiment) is always on the X-axis The dependent variable (the factor that is being measured during an experiment) is always on the Y-axis

Best Fit Line Questions on this? (0,0) is not always the best starting point for best fit lines, if the origin is not a valid data point PLEASE LABEL YOUR GRAPHS AND TABLES Titles, Axes Labels, Units, etc. Algebra and Graphs Anyone know the equation for a linear relationship between two points? Slope? Challenge:

If the data collected did not give a straight bestfit line, and it happened to be parabolic, what is the equation for a quadratic relationship? y = ax2 + bx + c What if it was exponential growth or decay? Exponential but plateaus? Conclusion The answer to the hypothesis based on the data obtained from the Retest

In order to verify the results, experiments must be retested. Acceptance of Scientific Ideas After you analyze results, next you have to publicize them. There is a system of review all scientists follow to check their work, and it is called peer review. Peer review is when many different

scientists review your work and either approve, or disapprove it. Approved work is published and made available to the public. Unapproved work is not published at all. Acceptance of Scientific Ideas After results have been published, they are usually replicated many times. When a hypothesis has been tested over and over and is generally accepted by scientists, it becomes a theory.

Theories are based on scientific laws. A law is an explanation of the natural world that has no exceptions. Example: The Big Bang Theory Theory of Gravitation Sciences are integrated, so it is important to know something of each. Technology = science put to work/use.

Scientific theory = an explanation that has been tested by repeated observation; simple explanation of observations that leads to further predictions. Scientific law = observation of nature without explanation. Example: Law of gravity. Data may be qualitative

(descriptive words), or quantitative (numbers). Data may lead to a change, or update, in a theory. Example: Caloric theory Kinetic theory Models (computer, physical, illustrated) may be used to aid in predictions, and to represent reality.

The Way Science Works Be sure to test only one variable at a time. Remember that no experiment is a failure because it still brings about more data/observations. Tools of science include the fancy specialized tools, as well as the logic of critical thinking, and the basic physical observation. Solving a Problem

1) Identify a Problem 2) State Observations about the problem 3) Form a Hypothesis about the problem (ifthen) 4) Design an Experiment to test the hypothesis 5) Collect Data 6) Form a Conclusion 7) Retest Measurements Precision versus Accuracy Precision is the degree of exactness of a measurement Accuracy is how well the results of a measurement agree with the real value; that is the accepted value as measured by a competent experimenters.

Therefore, (quick summary) use equipment correctly make all readings at eye level DO NOT guesstimate a value ask for help Accuracy vs. Precision Good accuracy Good precision Poor accuracy Good precision Random errors: reduce precision Poor accuracy

Poor precision Systematic errors: reduce accuracy Reporting Measurements Using significant figures Report Add what is known with certainty ONE digit of uncertainty (estimation) Math Review Conversions Anyone need to review, speak now?

Dimensional Significant Analysis? Digits Must Use These!! Significant Figures The valid digits in a measurement are called significant digits The last digit given for any measurement is the uncertain digit All nonzero digits in a measurement ARE significant Rules for counting significant figures are summarized below.

Zeros within a number are always significant e.g. Both 4,308 and 40.05 contain four significant figures Zeros that do nothing but set the decimal point MAY BE significant e.g. Thus, 470,000 has two significant figures (or 3, 4, 5, or even 6!!!) Trailing zeros that aren't needed to hold the decimal point are significant e.g. 4.00 has three significant figures Sig. Figs. 2 46 5 1.9858e-3 3 .00746 3 21.0 4 .05343

4 1479. 6 2518.00 2 .049 3 392 4 .002241 3 1.67e-2 Sig. Figs. 1200 2 1200. 4

120.0 4 2.9813 x 10-12 5 0.004 1 .004 1 0.0043

2 0.00430 3 123456789 9 (maybe 3 or 4) Significant Figures If you are not sure whether a digit is significant, assume that it isn't For example, if the directions for an experiment read: "Add the sample to 400 mL of water," assume the volume of water is known to one significant figure Exact numbers are known with complete certainty

Try this one: 5,280 feet in a mile how many significant figures? In addition and subtraction, the result is rounded off to the last common digit occurring furthest to the right in all components In other words, the result is rounded off so that it has the same number of decimal places as the measurement having the fewest decimal places For example: 104.630 + 27.08362 + 0.61 = 132.32362 This should be rounded to 132.32 (2 decimal places) Significant Figures In multiplication and division, the result should be rounded off so as to have the same number of significant figures as in the component with the

least number of significant figures For example: 3.0 (2 sig figs ) 12.60 (4 sig figs) = 37.8000 Round it off to 38 (2 significant figures) The answer in a calculation cannot be more precise than the values in the calculation. How many decimal places are needed? How many sig. figs. in the answer? 4.389 11235 + 812.1233 + 128.1 =

* 1234 * 87 = 2 1 49837 1.1234 12.5223 + 9.998 = 3 871.12598 + 1238.71238 = 5 34.23491 = 5

0.00691 * 4.001 * 580001 = 3 Sig. Figs. Continued DANGER Laboratory Safety Rules Laboratory Equipment Laboratory Equipment Safety Symbols Eye Protection Required

Heat Protection Clothing Protection Required Glassware Safety Hand Protection Required Laboratory Hygiene Chemical Safety

Sharp Object Hazard Caustic Substance Waste Disposal Safety Symbols SAFETY CLOTHING This symbol is to remind you to wear a laboratory apron over your street clothes to protect your skin and clothing from spills. SAFETY GOGGLES This symbol is to remind you that safety goggles are to worn at all times when working in the laboratory. For some activities, your teacher may also instruct you to wear protective gloves.

GLOVES This symbol is to remind you to wear gloves to protect your hands from contact with corrosive substances, broken glass, or hot objects. HEATING This symbol indicates that you should be careful not to touch hot objects with your bare hands. Use either tongs or heat-proof gloves to pick up hot objects.. FIRE This symbol indicates the presence of an open flame. Loose hair should be tied back or covered, and bulky or loose clothing should be secured in some manner. DANGEROUS VAPORS This symbol indicates the presence of or production of poisonous or noxious vapors. Use the fume hood when directed to do so. Care should be taken not to inhale vapors

directly. When testing an odor, use a wafting motion to direct the vapor toward your nose. EXPLOSION This symbol indicates that the potential for an explosive situation is present. When you see this symbol, read the instructions carefully and follow them exactly.. POISON This symbol indicates the presence of a poisonous substance. Do not let such a substance come in contact with your skin and do not inhale its vapors. ELECTRICAL SHOCK This symbol indicates that the potential for an electrical shock exists. Read all instructions carefully. Disconnect all apparatus when not in use. RADIATION This symbol indicates a radioactive substance. Follow your teacher's instructions as to proper handling of such substances.. CORROSIVE SUBSTANCE

This symbol indicates a caustic or corrosive substance - most frequently an acid. Avoid contact with skin, eyes, and clothing. Do not inhale vapors. DISPOSAL This symbol indicates that a chemical should be disposed of in a special way. Dispose of these chemicals as directed by your teacher. BREAKAGE This symbol indicates an activity in which the likelihood of breakage is greater than usual, such as working with glass tubing, funnels and so forth. HYGIENE This symbol is to remind you to always wash your hands after completing a laboratory investigation. Never touch your face or eyes during a laboratory investigation.

Chemical Burns Flammable Health Reactive Special Skin burned by chemicals Chemical burns on feet. The Bunsen Burner Oxidizing flame Hottest part M i x t r

e Barrel o f G A S a n d A I R Collar Air Spud

Gas The Bunsen Burner Oxidizing flame Hottest part M i x t r e Barrel o f G

A S a n d A I R Collar Air Spud Gas Robert Bunsen Lighting a Bunsen Burner gas valve

outer, transparent, dim blue cone inner, less transparent, brighter, greenish-blue cone air adjustment gas adjustment Always light match BEFORE turning on gas. Flame Temperature Distribution Bunsen / Tirrill

Burner Flame 1540oC 1550oC 1560oC 1540oC 1470oC 1560oC 520oC 1450oC 350oC 300oC 1640oC 1660 C o Meker Burner Flame 1660oC

1660oC 1670oC 1670oC 1720oC 1720oC 1680oC 1720oC 1775oC The Bunsen / Tirrill burner and Meker burner differ not only in the higher maximum temperature produced, but also in heat distribution within the flame. Properties of Matter Physical Properties Physical properties can be observed without a chemical

change/new product. Dissolving is a physical change. Physical properties include color, size, shape, density, taste, smell, feel, sound, texture, melting point, boiling point, strength, hardness, solubility, conductivity, What are the states of matter? Chemical properties describe how a substance reacts.

Size, shape, texture may change, but it is still the same stuff. Chemical Properties Some elements are very reactive and occur in nature combined with other elements. Other elements are nonreactive, such as gold.

A chemical reaction or change results in the production of: New substance new color odor or gas precipitate change in energy Physical Property - Density

Density: The ratio of Mass to Volume Mass is the amount of material that makes a substance Volume is the amount of space the object physically occupies in a three-dimensional space Besides measuring length, width, & height, what is another method of measuring volume? Since density is a physical property, it can be used to identify substances Chemical Property A chemical property is one that describes how a substance reacts

and thus subsequently changes into something else These are also known as Chemical Reactions Reactan (II) oxide mercury Product mercury + ts s oxygen Physical and Chemical Properties Examples of Physical Properties Boiling point

Color Slipperiness Electrical conductivity Melting point Taste Odor Shininess (luster) Softness Dissolves in water Ductility (form wire) Volatility (vapor) Hardness Malleability Viscosity (resistance to flow)

Density (mass / volume ratio) Examples of Chemical Properties Burns in air Reacts with certain acids Decomposes when heated Explodes Reacts with certain metals Reacts with certain nonmetals Tarnishes Reacts with water Is toxic

Chemical properties can ONLY be observed during a chemical reaction! Intrinsic Characteristics or properties of matter that DO NOT depend on the amount of matter present These characteristics do not change with changing amounts of matter These can be used to find the identify of an unknown sample Extrinsic Characteristics

or properties of matter that DO depend on the amount of matter These properties change with changing quantities Mass, volume, weight, etc. Phase, color, taste, texture, density, solubility, melting/boiling point, etc. Intrinsic vs Extrinsic Properties End of Chapter 1

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