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Chapter 1 Why study chemistry? ◦ Chemistry – the study of matter and the changes it undergoes. ◦ Why is this important to me? Two real-life events involving two discoveries can help answer this question. The refrigerator Energy from the sun The Ozone Layer ◦ Sunburns result from the ultraviolet (UV) radiation from the sun. ◦ Overexposure to UV radiation is harmful to plants and animals. UVB can cause cataracts and skin cancer in humans UVB can cause lower crop yields in agriculture UVB can cause disruption in food chains in nature Earth’s Atmosphere ◦ Living organisms on Earth exist due to protection from high levels of UVB ◦ What offers this protection? Ozone Ozone is made up of oxygen, O3 Ozone is a substance in the atmosphere that absorbs most harmful radiation before it reaches the Earth’s surface Earth’s Atmosphere ◦ Substance- also known as a chemical, is matter that has definite and uniform composition ◦ About 90% of Earth’s ozone is spread out in a layer that surrounds and protects our planet. ◦ Ozone layer is located in the stratosphere Ozone Formation ◦ How does ozone enter the stratosphere? When oxygen gas (O2) is exposed to UV radiation in the upper regions of the stratosphere, ozone (O3) is formed Energy from UV radiation breaks O2into individual oxygen particles (O), which then interact with O2 to form O3 Chlorofluorocarbons (CFCs) ◦ Is a substance that consists of chlorine, fluorine, and carbon ◦ Several different substances are classified as CFCs ◦ CFCs are nontoxic and stable—do not readily react with other substances ◦ By 1935, they seemed ideal for coolants in refrigerators and propellants in spray cans Chlorofluorocarbons (CFCs) ◦ 1970s Scientists began detecting CFCs in the atmosphere After measuring the amount of CFCs in the stratosphere, it was evident the amount increased yearly Consequently the ozone layer was thinning Chemistry and Matter Matter and its characteristics ◦ Matter, the stuff of the universe, has many different forms. ◦ Some occurs naturally, such as ozone ◦ Some do not occur naturally, such as CFCs ◦ Mass – is a measurement that reflects the amount of matter Mass and weight ◦ Weight – the measurement not only of the amount of matter but also of the effect of the Earth’s gravitational pull on that matter Structure and observable characteristics ◦ What can you observe about the outside of our school building? ◦ What can’t you see from the outside? ◦ What about when you bend your arm? ◦ Macroscopic – visible to the naked eye; no need for a microscope ◦ Submicroscopic – too small to be seen through a microscope Atoms are so small they are submicroscopic Structure and observable characteristics ◦ Chemistry seeks to explain submicroscopic events that lead to macroscopic observations. ◦ Scientists use models Model – is a visual, verbal, or mathematical explanation of experimental data Chemistry: The central science ◦ A basic understanding of chemistry is central to all sciences—biology, physics, Earth science, ecology and more ◦ Chemistry is broken down into different branches that focus on specific areas Chemistry: The central science ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Organic chemistry Inorganic chemistry Physical chemistry Analytical chemistry Biochemistry Environmental chemistry Industrial chemistry Polymer chemistry Theoretical chemistry Thermochemistry Scientific Methods One day, you come home from the movies and find it’s dark inside your house. You flip the light switch and nothing happens. What do you do? What could have happened to the light? A systematic approach ◦ Scientific method – is a systematic approach used in scientific study, whether it is chemistry, biology, physics, or another science. Observation ◦ Observation is the simple act of gathering information. ◦ The first type of observation is qualitative data Qualitative data – information that describes color, odor, shape, or some other physical characteristic. Anything that relates to the five senses is qualitative ◦ Another type of data is quantitative data Quantitative data – this is numerical information Hypothesis ◦ Hypothesis – is a tentative explanation for what has been observed ◦ There is no formal evidence to support a hypothesis when it is made ◦ A hypothesis is meaningless without data to support it. Experiments ◦ Forming a hypothesis helps the scientist focus on the next step—experiment. ◦ Experiment – is a set of controlled observations that test the hypothesis. ◦ Independent variable – the variable that you plan to change ◦ Dependent variable – its value changes in response to a change in the independent variable Other factors ◦ Constant factors are not allowed to change throughout the experiment ◦ Control – a standard for comparison Controlling variables ◦ Sometimes it is easier to simulate conditions in a laboratory, where variables can be controlled. ◦ Interactions between CFCs and ozone, are harder to study in the stratosphere with so many variables Conclusion ◦ Conclusion – is a judgment based on the information obtained ◦ A hypothesis can never be proven ◦ Data can support the hypothesis, which can indicate that the hypothesis may be true ◦ If further evidence does not support the hypothesis it must be discarded or modified ◦ Majority of hypotheses are not supported, but can yield helpful information Theory and Scientific Law ◦ Theory – is an explanation of natural phenomenon based on many observations and investigations over time Einstein’s theory of relativity Atomic theory ◦ Scientific Law – a relationship in nature that is supported by may experiments Newton’s laws Scientific Research Types of Scientific Investigations ◦ Pure research – to gain knowledge for the sake of knowledge itself ◦ Applied research – is research undertaken to solve a specific problem Chance discoveries ◦ Alexander Flemming Penicillin ◦ Julian Hill Nylon Students in the Laboratory ◦ Write down ten rules that you believe would be found within a laboratory environment. The Story Continues ◦ The Montreal Protocol In 1987, Montreal Protocol was signed Worked to phase out the global use of CFCs ◦ The ozone hole today Models show it will begin to recover The benefits of chemistry ◦ Involved in Finding cures or vaccines for diseases such as AIDS and influenza Cars Lasers Plastics Technology And much more