Chemistry: the Study of the Composition of Matter and the Changes It Undergoes

Notes: Section 1.1

Chemistry: The study of the composition of matter and the changes it undergoes.

Pure Science vs. Technology

Pure Science: Learning about science for the sake of increasing your knowledge.

Technology (Applied Science): Applying knowledge learned in pure science for something useful in society. (With Risk and Benefit)  Pure Science and Technology work together to improve our way of living  Technology allows us to use better methods of advancing our knowledge.

Qualitative measurements: A measurement that gives descriptive, nonnumeric results.  Observations which identify the qualities of a substance. (color, shape, texture, etc.)

Quantitative measurements: A measurement that gives definite, usually numeric results.  Observations which describe amounts (quantities). Examples: mass, volume, density, etc.

Accuracy: How close the measurement is to the accepted (True) value.

Precision: How close several measurements agree with each other.

Example (precise but not accurate):  I throw 3 darts that hit the 18 on the dart board but I was aiming at the bull’s eye.

Example (accurate and precise)  I throw 3 darts that hit the bull’s eye on the dart board and I was aiming at the bull’s eye.

Composition of air near the Earth's surface

 78% Nitrogen (N2)

 21% Oxygen (O2)  0.9% Argon (Ar)

 < 0.01% of Helium (He), Neon (Ne), Carbon Dioxide (CO2), variable amounts of water (H2O), and other

pollutants like NO2, SO2, etc.

Smog:  Smog is a kind of air pollution that produces a fog or smoke appearance in the air.

 Classic smog is a result of smoke and sulfur dioxide, SO2, pollutants combining when burning large amounts of coal.  Modern smog is a photochemical effect from the exhaust of automobiles or industry. The high temperatures in the engine of an automobile caused by burning gasoline with air makes the nitrogen and oxygen in the air form a harmful pollutant called nitrogen oxide. These pollutants combine with dust to make highly reactive molecules that are dangerous to inhale. Modern automobiles have catalytic converters added to the exhaust system to reduce the emission of these harmful nitrogen oxide gases. Notes: Section 1.2

Pollution Effects Acid Rain :

Polluting gases like carbon monoxide (CO), Carbon dioxide (CO2), Sulfur dioxide (SO2), and Nitrogen oxide

(NOx), combine with water (H2O) in the air to form acid rain. Source of polluting gases

CO and CO2 form Carbonic acid, H2CO3 (a weak acid)

SO2 gases combine with water to form Sulfuric acid, H2SO4 (a strong acid)

NOx gases combine with water to form Nitric acid, HNO3, (a strong acid)

 Acid rain has been very devastating to any statues made from marble. Marble (calcium carbonate) reacts with acid to form carbon dioxide. Many statues have faced extreme deterioration since the industrial age has allowed more polluting gases into our atmosphere and our rainwater is slightly acidic (pH of 5.5).  Note: neutral water has a pH of 7.0, strong acids have a pH of 1.0 and strong bases(alkaline substances) have a pH of 14.

The Greenhouse Effect:  The greenhouse effect is trapped energy from the sun heating up a place higher than normal. This is similar to what happens inside a car sitting in the sun during the day. The temperature inside the car is much higher than the temperature outside the car due to trapped sunlight. If our atmosphere gets thick enough, then the surface temperature of the earth will also increase due to the “Greenhouse effect”

 The build up of Carbon dioxide in our atmosphere has been apparently altering weather patterns.

 Experiments have shown that there really is more CO2 in our air than there was when the testing started in mid-1970s. It is unclear what is causing the change. (It may be a result of more fuels being burned, or it could be a natural process, or due to the rain forest and many other trees being

cut down every year so less CO2 is purified by plants in photosynthesis)

Ozone (O3):  Ozone gas is a protective layer of our upper atmosphere. Its existence blocks harmful high-energy radiation from space (gamma rays). It is believed that our use of freon and other CFC’s (Chloro- Fluoro-Carbons) have resulted in the deterioration of the ozone layer (Ozone Depletion).

 Ozone is produced by electrical discharge.

Ozone Depletion:  One Chlorine or Fluorine atom can destroy millions of ozone molecules by causing a chain reaction

where O3 breaks up and keeps forming O2.  Possible consequences of ozone depletion:  Increased risk of skin cancer.  Death to certain forms of plankton in the sea. Plankton is a beginning source of food in the food chain.

Photosynthesis

Plants use energy from the sun to make sugar and oxygen. All energy we get ultimately comes from the sun.

Word Equation: Carbon dioxide + water + Sun’s energy  Glucose + Oxygen (a Sugar)

Chemical Equation:

6 CO2 + 6 H2O + Sun’s energy  C6H12O6 + 6 O2

The reaction can also be reversed. When we consume plants we get energy to work, play, or just stay warm.

Reverse Equation: Sugar + oxygen  water + carbon dioxide + energy

Chemical Equation: (Fill in the blanks with the formulas for oxygen, water, and carbon dioxide)

C6H12O6 +  + + energy

All chemical reactions undergo energy changes. Either the reaction needs energy to continue the reaction (endothermic) or energy is produced by the reaction (exothermic).

Thinking Like a Scientist: Section 1.3

Scientific Method: The manner in which scientists proceed to solve a problem. 1. Observe nature. 2. Find order. (Search for scientific laws) 3. Form hypotheses 4. Conduct experiments to test your hypothesis. Repeat steps 1-4. 5. TheoryExplain and Predict (Modify theories as new evidence arises)

Observations: Using your senses to gather information. Look for patterns or order in nature (Laws).

Scientific Laws (Fact): A concise statement that summarizes the results of many observations and experiments. A scientific law describes a natural phenomenon without trying to explain it.  Statement of a relationship between observed facts. (Describes patterns in nature)  Generally summarized with a mathematical expression. i.e. Density = mass/volume

Hypothesis: Proposed explanation of observed facts or events that need further experimentation. Hypotheses are tested through experimentation and making further observations. Experiment: Carry out a procedure under controlled conditions. Experimentation yields data that result in the discarding, modification, or adoption of a hypothesis.

Theory: A generally accepted explanation of a scientific problem. Theories are based on many observations supported by experimental results and are a summation of several hypothesis statements. Theories explain scientific laws and are used to predict outcomes. Theories can be modified!!!