Chemistry Lecture - Atoms, Molecules, and the Scientific Method

The Chemical World Chemistry: The science that seeks to understand what matter does by studying what atoms and molecules do. Virtually everything around you is composed of chemicals. © 2018 Pearson Education, Inc.  Chemicals Compose Ordinary Things Peop...

The Chemical World Chemistry: The science that seeks to understand what matter does by studying what atoms and molecules do. Virtually everything around you is composed of chemicals. © 2018 Pearson Education, Inc.  Chemicals Compose Ordinary Things People often have a very narrow view of chemicals, thinking of them only as dangerous poisons or pollutants. © 2018 Pearson Education, Inc.  Chemicals Compose Ordinary Things Chemicals compose ordinary things, too. The air we breathe The water we drink Toothpaste, Tylenol, toilet paper © 2018 Pearson Education, Inc.  Atoms and Molecules in Matter Atoms are very small. Atoms and molecules are tiny particles that compose all common matter. The atoms are bound together to form several different types of molecules. Chemical bonds are the attachments that hold atoms together. © 2018 Pearson Education, Inc. Molecular models- Ball and stick model- atoms are represented by colored balls linked together with sticks. Red = Oxygen White = Hydrogen Black = Carbon Blue = Nitrogen Yellow = Sulfur  Water Molecules Water molecules consist of three atoms—one oxygen and two hydrogen—bonded together, and the water molecule is bent. The characteristics of water molecules make water a liquid at room temperature. © 2018 Pearson Education, Inc.  Chemicals Compose Ordinary Things © 2018 Pearson Education, Inc.  The Scientific Method: How Chemists Think Ways to Understand the World: Chemists use the scientific method—a way of learning that emphasizes observation and experimentation—to produce knowledge as the result of the senses. © 2018 Pearson Education, Inc.  Ancient Philosophy and Medieval Applications The scientific method stands in contrast to ancient Greek philosophies and medieval applications of them that emphasized reason to produce knowledge as the result of thoughts. © 2018 Pearson Education, Inc.  The Scientific Method: How Chemists Think Knowledge as a Result of the Senses: Observations involve measuring or observing some aspect of nature. Hypotheses are tentative interpretations of the observations. Laws summarize the results of a large number of observations. Theories are models that explain and give the underlying causes for observations and laws. © 2018 Pearson Education, Inc.  The Scientific Method: Experiments Hypotheses, laws, and theories must be tested and validated by experiment. If hypotheses are not confirmed, they are revised and tested through further experimentation. © 2018 Pearson Education, Inc.  The Scientific Method: Observation Some observations can be made with the naked eye. Other observations emerge from experiments that rely on the use of sensitive instrumentation. Observation usually involves the measurement or description of some aspect of the physical world. © 2018 Pearson Education, Inc.  Observation of Combustion Antoine Lavoisier (1743–1794), a French chemist, made an observation about the physical world. Lavoisier measured the property of mass in the process of combustion. The mass of an object is a measure of the quantity of matter within it. Combustion means burning. © 2018 Pearson Education, Inc.  Observation of Combustion Experiments Lavoisier burned substances in closed containers. He measured the mass of each container and its contents before and after burning the substance inside. He noted that there was no change in the mass during combustion. © 2018 Pearson Education, Inc.  The Scientific Method: Hypothesis Observations lead scientists to formulate a hypothesis, a tentative interpretation or explanation of the observations. A good hypothesis is falsifiable, which means that further testing has the potential to prove it wrong. Hypotheses are tested by experiments, highly controlled observations designed to validate or invalidate hypotheses. The results of an experiment may confirm a hypothesis or show it to be mistaken in some way. The hypothesis may have to be modified or discarded and replaced by an alternative. The new or revised hypothesis must also be tested through further experimentation. © 2018 Pearson Education, Inc.  Law of Conservation of Mass A number of similar observations lead to the development of a scientific law, a brief statement that synthesizes past observations and predicts future ones. Lavoisier developed the law of conservation of mass, which states, “In a chemical reaction, matter is neither created nor destroyed.” © 2018 Pearson Education, Inc.  The Scientific Method: Scientific Theory One or more well-established hypotheses may form the basis for a scientific theory. Theories provide a broader and deeper explanation for observations and laws. Theories are models of the way nature is. Theories often predict behavior that extends well beyond the observations and laws on which they are founded. © 2018 Pearson Education, Inc.  The Scientific Method: Observation, Law, Theory Classify each statement as an observation, a law, or a theory. (a) When a metal is burned in a closed container, the mass of the container and its contents does not change. (b) Matter is made of atoms. (c) Matter is conserved in chemical reactions. (d) When wood is burned in a closed container, its mass does not change. © 2018 Pearson Education, Inc.  The Scientific Method: Overview © 2018 Pearson Education, Inc.  The Scientific Method: Experiments Scientific theories are tested and validated by experiments. If a law, hypothesis, or theory is inconsistent with the findings of an experiment, it must be revised and new experiments must be conducted to test the revisions. Over time, poor theories are eliminated and good theories—those consistent with experiments—remain. © 2018 Pearson Education, Inc.  The Scientific Method: Scientific Theories Established theories with strong experimental support are the most powerful pieces of scientific knowledge. People unfamiliar with science sometimes say, “That is just a theory,” as if theories were mere speculations. Well-tested theories are as close to truth as we get in science. © 2018 Pearson Education, Inc.  The Scientific Method: Atomic Theory The idea that all matter is made of atoms is a theory with two hundred years of experimental evidence to support it. Modern technology provides recent images, such as this one, of atoms themselves. This image shows the Kanji characters for “atom” written with individual iron atoms on top of a copper surface. © 2018 Pearson Education, Inc.  Chemistry Requires Calculation Quantification involves measurement as part of observation—it is one of the most important tools in science. Quantification allows you to specify the difference precisely. For example, two samples of water may feel equally hot to your hand, but when you measure their temperatures, you may find that one is 40 °C and the other is 44 °C. © 2018 Pearson Education, Inc.