Science is a search for truth.
Truth is the way things are.

Scientists are NOT holders of truth. They are skeptics, always questioning what we think we understand.

The Scientific Method:

1. State the problem
2. Research the problem
3. Form a hypothesis
4. Test the hypothesis
5. Draw Conclusions

Science involves communication.

Everything scientists write is an argument, from a memo, to a journal publication, to a grant proposal − each is a document written to convince.

An ability to argue clearly and convincingly is essential. Today's professional must have presentation skills of all types from writing, to speaking, to preparing effective electronic posters for meetings.

Literacy is being able to publish in the mode of your audience. The realms where we publish change and are increasing in number daily. For example, to be literate in "casual" communication (such as texting or IM), you must be able to publish in that medium. For "formal" communication (such as business letters or papers), you need the ability to publish in a formal form. And the rules for these two are VERY different.

• Always write in complete sentences.
• Learn to write without "first person statements".

  Example: instead of writing "I think chemistry is fun", write "Chemistry is fun".

• Paragraph evaluationUnderstanding Essays and evaluation
• Understanding Scientific Papers and evaluation

A Paragraph

 
Chemistry is the study of the properties of materials and the changes that materials undergo.

This class will include several of the subdisciplines of chemistry. Much of our time will be in the area of inorganic chemistry. Emphasis will be placed on the Periodic Table and how it represents the current atomic theory. Other areas will include theoretical, analytical, organic, and nuclear chemistry.

Matter is composed of elementary substances called elements.

Atoms are the building blocks of matter. Molecules are formed by two or more atoms combining in specific shapes.

 
Classification of Matter

Matter is classified according to its physical state - solid, liquid, or gas - and according to its composition - element, compound, or mixture.

Physical States

The particles of a gas (the gaseous phase of a substance that is normally a solid or liquid at room temperature is often called a vapor) are far apart, moving at high speeds, and repeatedly collide with the walls of the container.

The particles of a liquid are packed more closely together, but still move rapidly enough to slide over each other - allowing them to be easily poured.

The particles of a solid are held tightly together, usually in definite arrangements, in which the particles can only vibrate around fixed position.

A pure substance has distinct properties and a composition that doesn't vary from sample to sample.

A mixture is a combination of two or more pure substances in which each substance retains its own chemical identity.

At the present time 116 elements are known. Five elements make up over 90% of the earth's crust: oxygen, silicon, aluminum, iron, and calcium. Three elements make up over 90% of the human body: oxygen, carbon, and hydrogen.

The substances making up a mixture are its components. Although the components are mixed together, they each retain their individual characteristics.

• Heterogeneous mixtures do not have the same composition, properties, and appearance throughout.
   
• Homogeneous mixtures are uniform throughout. These mixtures are also called solutions.
   
  • The substance present in the greatest amount in a solution is the solvent.
     
  • All other substances in the solution are solutes.

Properties of matter can be categorized as physical or chemical.

• Physical properties can be measured without changing the identity and composition of the substance - color, odor, density, melting point, boiling point, and hardness.
   
• Chemical properties describe the way a substance reacts to form other substances.

Extensive properties - such as mass and volume - depend on the quantity of the sample.

Quantitative properties - such as mass, volume, and melting point - are associated with numbers.

Qualitative properties - such as color, odor, and texture - have no association with numbers.

Properties of Matter

 
Changes in Matter

• During a physical change, a substance changes its physical appearance, but NOT its composition.
  All changes of state are physical changes.

• During a chemical change, a substance becomes a chemically different substance.
  All chemical reactions are chemical changes.

 
Lab Safety     MSDS

 
Separating Parts of a Mixture

 
International System of Units, SI

In 1960 an international agreement was reached specifying a particular choice of metric units for use in scientific measurements. The SI base units are shown in the table below.

Notice the SI base unit for mass is the only base unit with a prefix.

The SI base unit of temperature is the Kelvin, K.

Derived units - those involving a calculation with base units.

• Area - length squared
• Volume = length cubed - cm³ (say "cubic centimeters" not "centimeters cubed")
  1 cm³ = 1 ml

  One cubic decimeter is equal to one liter

• Density = mass / volume
  The density of water at 4 ^oC is 1 g/cm³.

Temperature Scales

The Fahrenheit scale is not used in science - except possibly when reporting human body temperature.

The Celsius scale is used for reporting most temperatures in chemistry.

The Kelvin scale is used for gas law calculations and for extreme temperatures. There are no numbers below zero on this scale. Zero on the Kelvin scale is absolute zero, the point at which all molecular motion stops.

The degree graduations on the Kelvin and Celsius scales the same distance apart.

 
Uncertainty in Measurement

Exact numbers are those whose values are known exactly. Inexact numbers are those whose values have some uncertainty.

Numbers obtained by measurement are always inexact. There are inherent limitations in the measuring equipment and in the ability of the person using the equipment.

Measured quantities are generally reported in such a way that only the last digit is "estimated".

Precision describes how closely individual measurements agree with one another. Accuracy describes how closely individual measurements agree with the "true" value.

Scientific Measurement

 
Significant Figures

All digits of a measured quantity, including the uncertain one, are called significant figures. The greater the number of significant figures, the greater the implied certainty for the measurement.

With "exact" numbers, such as "12 inches equals 1 foot", the numbers are treated as if they have an infinite number of significant figures.

1. In any properly reported measurement, all nonzero digits are significant.

2. Zeros can be part of the measured value or merely place holders for the decimal point - so they may or may not be significant.

   These guidelines describe the different situations involving zeros:

    
   • Zeros at the beginning of a number are never significant (0.2)
      
   • Zeros used only to space the decimal point are never significant (0.005)
      
   • Zeros between nonzero digits are always significant (1005)
      
   • Zeros at the end of a number are significant, if the number contains a decimal point (0.200).

     If a number ends with zeros but does not contain a decimal point, it is normally assumed that the zeros are just spacing the decimal and are not significant. (2500)
      

   • Proper scientific notation begins with the measured numbers that are significant written with only one number to the left of a decimal point. The zeros spacing the decimal point are indicated by the exponential notation and are not significant.
     

    

Significant Figures

 
Dimensional Analysis − the most important mathematical process in chemistry.

Units in chemistry are just as important as numbers. Dimensional analysis carries units through all calculations. Whatever mathematical operation is done with the numbers is also done with the units. When the final units match the desired units, the problem has been solved correctly.

Dimensional analysis can be set up as cross multiplication:

Dimensional analysis can be set up like this:

The key to dimensional analysis is the correct use of conversion factors to change one unit to another. A conversion factor is a fraction whose numerator and denominator are the same quantity expressed in different units.

Since both numbers in a conversion factor are equal, the fraction can be written with either one on top.

The thing that determines which one is put on top is which one is needed to cancel the given unit.

 
First sample problem - with one unit to convert.

Convert 1 year into seconds.

1. Beginning with the given number, multiply all numbers across the top from left to right.
    
2. Without hitting the equal button, divide by all the numbers across the bottom from right to left.
    
3. Finally, hit the equal button one time to get the final numerical answer.

Convert 65 miles per hour into meters per second.

(TIP: only one unit can be converted at a time.)

Dimensional Analysis
 

Experimental Error

The comparison of a value obtained by experimentation to an accepted "theoretical" value. This calculation is used to determine how well experimental measurements are done.

Dimensional Analysis & Experimental Error

Favorite Historical Science Figure Web Page