Introduction to Chemistry

Page 1

• Introduction to Chemistry

  • Chemistry and matter are related

  • Scientific methods can be used to solve problems

  • Difference between scientific research and technology

• Importance of studying matter

  • Understanding of the body and everyday life

Page 2

• The Stories of Two Chemicals

  • Formation and importance of ozone

  • Development of chlorofluorocarbons

• Discovery Lab

  • Procedure for measuring the mass of a burned match

  • Analysis of the change in mass

  • Importance of ozone in protecting against ultraviolet radiation

  • Definition of a chemical and the composition of ozone

Page 3

Earth's atmosphere

• The atmosphere consists of layers

  • The lowest layer is called the troposphere

  • The troposphere contains the air we breathe

  • All of Earth's weather occurs in the troposphere

  • The stratosphere is the layer above the troposphere

  • The ozone that protects Earth is located in the stratosphere

Ozone formation

• Ozone is formed when oxygen gas is exposed to ultraviolet radiation in the upper regions of the stratosphere

• Ozone can absorb radiation and break apart to reform oxygen gas

• Ozone forms over the equator and flows toward the poles

• G.M.B. Dobson measured the amount of ozone in the atmosphere

• In October 1985, a confirmed decrease in the amount of ozone in the stratosphere was reported

Figure 1-1

Earth's atmosphere consists of several layers. The layer nearest Earth is the troposphere. The stratosphere is above the troposphere.

Figure 1-2

The troposphere extends to a height of about 15 km. Cumulonimbus clouds, or thunderheads, produce thunder, lightning, and rain.

Topic: G.M.B. Dobson

To learn more about G.M.B. Dobson, visit the Chemistry Web site at chemistrymc.com

Activity: Research the work of G.M.B. Dobson. Make a graph of his measurements by year.

Page 4

Figure 1-4

The thinning heel of this sock models the thinning of the ozone layer in the stratosphere. This colored satellite map of stratospheric ozone over Antarctica was taken on September 15, 1999. The lowest amount of ozone (light purple) appears over Antarctica (dark purple). Blue, green, orange, and yellow show increasing amounts of ozone.

• The thinning of the ozone layer is often called the ozone hole

• The ozone hole is not actually a hole, but a thinning of the protective layer

• Measurements from balloons, high-altitude planes, and satellites support the measurements made from the ground

What could be causing the ozone hole?

• Chlorofluorocarbons (CFCs)

  • CFCs were synthesized in the 1920s as safer coolants for refrigerators

  • CFCs consist of chlorine, fluorine, and carbon

  • They are nontoxic and stable

  • They were used as refrigerants, in plastic foams, and as propellants in spray cans

Figure 1-3

This model of the formation

Page 5:

• Refrigerators, air conditioners, aerosol cans, plastic foam cups, and food containers all contain or are made with CFCs

  • CFCs are stable chemicals

• Scientists noticed the presence of CFCs in the atmosphere in the 1970s

  • Quantities of CFCs in the stratosphere increased year after year

• Two separate occurrences were noticed: thinning of the ozone layer and increasing quantities of CFCs in the atmosphere

• Connection between the two occurrences is being investigated

Page 6:

• Chemistry is the study of matter and the changes it undergoes

• Chemistry is central to all sciences and everyday life

• Matter is found in various forms, including in our bodies, in our environment, and in everyday items

Page 7: Matter and its Characteristics

• Matter is anything that has mass and takes up space

• Mass is a measurement that reflects the amount of matter

• Air is matter because it expands and makes objects heavier

• Thoughts, ideas, heat, light, radio waves, and magnetic fields are not matter

Mass and weight

• Weight is a measure of the amount of matter and the effect of Earth's gravitational pull

• Weight varies in different locations due to differences in gravitational force

• Scientists use mass to measure matter independent of gravitational force

What you see and what you don't

• Buildings have internal structures that provide stability and function

Problem-solving LAB: Chemical Models

• Scientists discovered a new form of carbon called buckminsterfullerene

• Buckminsterfullerene has a unique structure resembling a soccer ball

• Examine the structure and identify the carbon atoms, connections, and shapes

• Chemists use models to represent structures that cannot be shown in photographs

• Colored particles in the model represent different elements

Figure 1-7

• A scale measures the downward pull of gravity on an object

• Weight readings would be different on the Moon compared to Earth

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• Matter and its behavior can be observed macroscopically

  • Example: bending your arm at the elbow

  • Muscles contract and relax to move your arm

• Matter can be broken down into elements

  • Over 100 types of matter called elements

  • Elements are made up of particles called atoms

  • Atoms are submicroscopic and cannot be seen with optical microscopes

  • 1 million million atoms could fit onto the period at the end of a sentence

• All matter can be explained on a submicroscopic level

  • Atoms and the changes they undergo

  • Chemistry explains submicroscopic events that lead to macroscopic observations

  • Models can be used to represent submicroscopic events

• Branches of chemistry

  • Organic chemistry

  • Inorganic chemistry

  • Physical chemistry

  • Analytical chemistry

  • Biochemistry

  • Theoretical chemistry

  • Environmental chemistry

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• Scientific methods

  • Common steps

  • Types of data (qualitative and quantitative)

  • Types of variables (independent and dependent)

  • Difference between a theory and a scientific law

• Scientific method as a systematic approach

  • Scientists try to understand their world based on personal point of view and creativity

  • Combining the work of many scientists to gain new insight

  • Using common procedures in experiments

  • Scientific method as an organized process used to do research and verify the work of others

• Steps of a scientific method

  • Not used as a checklist, can be done in different orders

  • Scientists must describe their methods when publishing results

  • Confirmation of results by other scientists is important for validity

• Observation as the starting point of scientific study

  • Observation as the act of gathering information

  • Qualitative data as the types of observations scientists first make

  • Qualitative data relates to the five senses

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• Chemists gather qualitative and quantitative data

  • Qualitative data: observations about qualities or characteristics

  • Quantitative data: numerical information

• Hypothesis

  • Chemists Molina and Rowland hypothesized that CFCs break down in the stratosphere due to interactions with ultraviolet light from the Sun

  • They also hypothesized that a chlorine particle produced by this interaction would break down ozone

• Experiments

  • An experiment is a set of controlled observations that test a hypothesis

  • Scientists must carefully plan and set up laboratory experiments to change and test one variable at a time

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• Independent and dependent variables

  • Temperature is the independent variable in an experiment testing the rate at which table salt dissolves

  • The rate at which the salt dissolves is the dependent variable

• Controlling variables

  • Other factors that could be varied in the experiment include the amount of salt, the amount of water, and stirring the mixture

  • These variables must be kept constant at each temperature to clearly determine the cause of the results

• Control and constant

  • A control is a standard for comparison in an experiment

  • In the example, the room-temperature water is the control

  • A constant is a factor that is not allowed to change during the experiment

  • In the example, the amount of salt, water, and stirring must be constant at each temperature

• Simulating conditions in a laboratory

  • It is sometimes easier to simulate conditions in a laboratory where variables can be more easily controlled

• Conclusion

  • Scientists form a conclusion based on the analyzed data and apply it to the hypothesis

  • A hypothesis can never be proven

Page 12

• The data support a hypothesis

  • Giving a tentative "thumbs up" to the idea that the hypothesis may be true

  • If further evidence does not support it, the hypothesis must be discarded or modified

  • The majority of hypotheses are not supported

  • Data may still yield new information

• Molina and Rowland formed a hypothesis about the stability of CFCs in the stratosphere

  • Gathered data that supported their hypothesis

  • Developed a model in which chlorine formed by the breakdown of CFCs would react with ozone

  • A model is a visual, verbal, and/or mathematical explanation of experimental data

  • A model can be tested and used to make predictions

• Molina and Rowland's model predicted the formation of chlorine and the depletion of ozone

  • Another research group found evidence of interactions between ozone and chlorine

  • They did not know the source of the chlorine

  • Molina and Rowland's model predicted a source of the chlorine

  • They concluded that ozone in the stratosphere could be destroyed by CFCs

  • They had enough support for their hypothesis to publish their discovery

• A theory is an explanation supported by many experiments

  • Theories can be modified based on new experimental data

  • Theories often lead to new conclusions

  • A theory is considered successful if it can make true predictions

• Scientific law is a relationship in nature supported by many experiments

  • No exceptions are found

  • Scientists develop further hypotheses and experimentation to explain why these relationships exist

Section 1.3 Assessment

1. What is a scientific method? What are its steps?

2. You are asked to study the effect of temperature on the volume of a balloon

   • The independent variable is temperature

   • The dependent variable is the volume of the balloon

   • The factor held constant is the pressure

   • A control can be constructed by measuring the volume of a balloon at a constant temperature

3. Critique Molina and Rowland's hypothesis of ozone depletion

   • Strengths: Gathered data that supported their hypothesis, developed a model that predicted the formation of chlorine and the depletion of ozone

   • Weaknesses: Another research group found evidence of interactions between ozone and chlorine but did not know the source of the chlorine

4. Should it be called Charles's law or Charles's theory?

   • It should be called Charles's law

   • Charles described the direct relationship between temperature and volume of all gases at constant pressure

5. Why must Molina and Rowland's data in the laboratory be supported by measurements taken in the stratosphere?

6. Is the statement about a specific diet protecting individuals from cancer a hypothesis or a conclusion?

   • It is a hypothesis

   • No data are reported to support the statement

     • Objectives

       • Compare and contrast pure research, applied research, and technology.

       • Apply knowledge of laboratory safety.

     • Types of Scientific Investigations

       • Pure research seeks knowledge for the sake of knowledge itself.

         • Molina and Rowland conducted research on CFCs and their interactions with ozone as pure research.

         • When the ozone hole was reported in 1985, their pure research became applied research.

       • Applied research is research undertaken to solve a specific problem.

         • Scientists continue to monitor CFC levels in the atmosphere and changes in ozone levels.

         • Applied research is being done to find replacement chemicals for banned CFCs.

     • Chance discoveries

       • Some scientific discoveries are made unexpectedly.

       • Example: the discovery of nylon by Wallace Carothers in 1934.

     • Students in the Laboratory

       • When working in the chemistry laboratory, students are responsible for their safety and the safety of others.

       • Table 1-2 lists safety rules for the laboratory.

     • Biology CONNECTION

       • Examples of unexpected discoveries by Alexander Fleming.

       • Discovery of lysozyme in mucus and tears.

       • Discovery of penicillin in mold.

   • Page 13: Chapter 1 Introduction to Chemistry Section 1.4 Scientific Research

     Page 14

     • Chemists and all other scientists use safety rules in the laboratory.

     • Developing Observation Skills

       • Observations and inferences are important in chemistry.

       • An inference is an explanation or interpretation of observations.

     • Procedure for miniLAB

       • Observing the effects of dishwashing detergent on water and milk.

       • Analysis of observations.

     Page 15: Safety in the Laboratory

     • Study lab assignment before coming to the lab

     • Ask teacher for help if there are any questions

     • Obtain permission from teacher before performing experiments

     • Use safety symbols and read caution statements

     • Wear safety goggles, laboratory apron, and gloves

     • Tie back long hair

     • Avoid wearing loose clothing, dangling jewelry, bare feet, and sandals

     • No eating, drinking, or chewing gum in the lab

     • Know location and usage of fire extinguisher, safety shower, fire blanket, and first-aid kit

     • Report accidents, injuries, incorrect procedures, or damaged equipment to teacher

     • Flush area with water if chemicals come in contact with eyes or skin

     • Handle chemicals carefully and read labels

     • Do not take reagent bottles to work area unless instructed

     • Do not return unused chemicals to stock bottle

     • Do not insert droppers into reagent bottles

     • Never taste chemicals or draw them into a pipette with mouth

     • Keep combustible materials away from open flames

     • Handle toxic and combustible gases under teacher's direction

     • Use fume hood when handling such materials

     • Be careful when heating substances in test tubes

     • Do not heat certain glassware with laboratory burner

     • Use caution when handling hot apparatus or glassware

     • Dispose of broken glass, unused chemicals, and reaction products as directed

     • Know correct procedure for preparing acid solutions

     • Keep balance area clean and do not place chemicals directly on balance pan

     • Clean and put away equipment after experiment

     • Wash hands before leaving the lab

     Page 16: Benefits of Chemistry

     • Applied research addresses specific problems and has immediate benefits

     • Pure research is important in unexpected events and provides a first line of defense

     • Technological applications of research result in products that improve human life

     • Technology is the practical use of scientific information

     • Advances in technology benefit us in various ways

     Section 1.4 Assessment

     • Compare and contrast pure research and applied research

     • Define technology and explain its relationship with research

     • Explain the importance of reading lab assignments before class

     • Discuss the reasons for wearing goggles and an apron, reporting accidents, and not returning unused chemicals to stock bottles

     • Identify safety precautions for different safety symbols

     Page 17:

     • Heat is the transfer of energy from a warmer object to a cooler object.

       • If an object feels warm to your finger, your finger is cooler than the object and energy is being transferred from the object to your finger.

       • If an object feels cooler to you, the energy flows from your finger to the object.

     • Your forehead is sensitive to hot and cold, which can be used to detect whether an object is giving off or absorbing heat.

     • It is important to read the entire CHEMLAB to know what the experiment is going to explore.

       • The problem that this experiment is going to explore is what happens when you heat a stretched rubber band.

     • The typical steps in a scientific method will be used to explore the problem.

       • The procedure for each experiment should be written down, including all safety precautions.

     • Data collected during each experiment should be recorded in data tables.

       • An example of a data table is provided for the Rubber Band Data Experiment.

     • Safety precautions for the experiment include observing the rubber band for any splits and handling the hair dryer with care.

     Page 18:

     • The experiment requires a large rubber band, a 500-g mass, a ring stand clamp, a hair dryer, and a meter stick or ruler.

     • The procedure for the experiment is as follows:

       1. Examine the rubber band for any splits or cracks.

       2. Record detailed observations of the unstretched rubber band.

       3. Design the first experiment to observe whether heat is given off or absorbed by a rubber band as it is stretched.

       4. Do repeated trials of the first experiment.

       5. Design the second experiment to observe whether heat is given off or absorbed by a rubber band as it contracts after being stretched.

       6. Do repeated trials of the second experiment.

       7. Use the observations from steps 2, 4, and 6 to form a hypothesis and make a prediction about what will happen to a stretched rubber band when it is heated.

       8. Design the third experiment to test what happens to a stretched rubber band as it is heated.

       9. Record all observations before, during, and after heating.

     • Cleanup and disposal instructions include returning the rubber band to the instructor and allowing the hair dryer to cool before putting it away.

     • The analysis and conclusion section includes questions about the observations and inferences made during the experiment.

     • Page 19:

       • Humans display remarkable and endless variety controlled by the human genome

         • The human genome is the complete "instruction manual" found in the nucleus of all cells

         • The Human Genome Project (HGP) aims to decode and understand these instructions

         • The project began in 1990 and is coordinated by the United States Department of Energy and the National Institutes of Health

         • Private industry is also involved in the project

         • The HGP fosters cooperation and competition among researchers

         • The goal is to advance the treatment of human genetic conditions

       • The fiftieth anniversary of Watson and Crick's recognition of the structure of DNA

         • The structure of DNA is made up of twisted strands connected by nitrogen bases

         • The human genome contains roughly three billion pairs of these bases

         • Determining the sequence of these base pairs was a common goal of researchers working on the HGP

       • Researchers approach the task from different angles

         • Biologists, chemists, physicists, computer specialists, and engineers are involved

         • Scientific methods are the unifying theme in all of this work

       • Prior to the HGP, researchers worked independently on decoding the human genome

         • Data collected were analyzed and stored using different databases

         • Data were shared only through scientific journals and conferences

       • The HGP used common methods for gathering and analyzing data

         • Results were shared through databases accessible via the World Wide Web

         • A rough map of the human genome was completed in February 2001

         • Efforts are underway to determine the exact location of every gene

         • Results will have to be shared by researchers working on the project

       • The HGP raises important ethical, legal, and societal issues

         • One issue is whether a person's genome map should be used to inform employers or insurance companies about predispositions for certain illnesses

         • These issues must be acknowledged and addressed

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       • Chemistry is the study of matter and the changes it undergoes

         • Matter is anything that has mass and takes up space

         • There are five traditional branches of chemistry: organic chemistry, inorganic chemistry, physical chemistry, analytical chemistry, and biochemistry

         • Macroscopic observations of matter reflect the actions of atoms on a submicroscopic scale

       • Scientific methods involve observation, hypothesis, experiments, data analysis, and conclusion

         • Qualitative data describe observations, while quantitative data use numbers

         • An independent variable is changed in an experiment, while a dependent variable changes in response to the independent variable

         • A theory is a hypothesis supported by many experiments, and a scientific law describes relationships in nature

       • Scient

         Page 21

         Chapter 1 Introduction to Chemistry

         • Go to the Chemistry Web site at chemistrymc.com for additional Chapter 1 Assessment.

         Concept Mapping

         • Complete the concept map using the following terms: stratosphere, oxygen gas, CFCs, ozone, ultraviolet radiation.

         Mastering Concepts

         • What is a chemical? (1.1)

         • Where is ozone located in Earth’s atmosphere? (1.1)

         • Explain the balance between oxygen and ozone in the stratosphere. Why is it important? (1.1)

         • What were common uses of CFCs? (1.1)

         • What is chemistry? (1.2)

         • Why is chemistry called the central science? (1.2)

         • Which measurement depends on gravitational force— mass or weight? Explain. (1.2)

         • Which branch of chemistry studies the composition of substances? Environmental impact of chemicals? (1.2)

         • How does qualitative data differ from quantitative data? Give examples of each. (1.3)

         • What is the function of a control in an experiment? (1.3)

         • What is the difference between a hypothesis, a theory, and a law? (1.3)

         • In the study of water, what questions might be asked in pure research? Applied research? Technology? (1.4)

         Thinking Critically

         • Compare and Contrast Why is CFC depletion of the ozone layer a theory and not a scientific law?

         • Classifying CFCs break down to form chemicals that react with ozone. Is this a macroscopic or a microscopic observation?

         • Communicating Ideas Scientists often learn as much from an incorrect hypothesis as they do from one that is correct. Explain.

         • Designing an Experiment How would you design an experiment to evaluate the effectiveness of a “new and improved” chemical fertilizer on bean plants? Be sure to describe your hypothesis, procedure, variables, and control.

         • Inferring A newscaster reports, “The air quality today is poor. Visibility is only a quarter mile. Pollutants in the air are expected to rise above 0.085 parts per million (ppm) in the next eight hour average. Spend as little time outside today as possible if you suffer from asthma or other breathing problems.” Which of these statements are qualitative and which are quantitative?

         • Comparing and Contrasting Match each of the following research topics with the branch of chemistry that would study it: water pollution, the digestion of food in the human body, the composition of a new textile fiber, metals to make new coins, a treatment for AIDS.

         Writing in Chemistry

         • Based on your beginning knowledge of chemistry, describe the research into depletion of the ozone layer by CFCs in a timeline.

         • Learn about the most recent measures taken by countries around the world to reduce CFCs in the atmosphere since the Montreal Protocol. Write a short report describing the Montreal Protocol and more recent environmental measures to reduce CFCs.

         • Name a technological application of chemistry that you use everyday. Prepare a booklet about its discovery and development.

         Cumulative Review

         • In chapters 2 through 26, this heading will be followed by questions that review your understanding of previous chapters.

         CHAPTER ASSESSMENT 1

         • is formed in the when breaks up is destroyed by

         chemistrymc.com/chapter_test

         Page 22: Standardized Test Practice

         • Matter is defined as:

           • a. exists in nature.

           • b. is solid to the touch.

           • c. is found in the universe.

           • d. has mass and takes up space.

         • Mass is preferred as a measurement over weight for all of the following reasons EXCEPT:

           • a. it has the same value everywhere on Earth.

           • b. it is independent of gravitational forces.

           • c. it becomes less in outer space, farther from Earth.

           • d. it is a constant measure of the amount of matter.

         • Which of the following is an example of pure research?

           • a. creating synthetic elements to study their properties

           • b. producing heat-resistant plastics for use in household ovens

           • c. finding ways to slow down the rusting of iron ships

           • d. searching for fuels other than gasoline to power cars

         • When working with chemicals in the laboratory, which of the following is something you should NOT do?

           • a. Read the label of chemical bottles before using their contents.

           • b. Pour any unused chemicals back into their original bottles.

           • c. Use lots of water to wash skin that has been splashed with chemicals.

           • d. Take only as much as you need of shared chemicals.

         Interpreting Tables and Graphs

         Use the table and graph to answer questions 5–7.

         • What must be a constant during the experiment?

           • a. temperature

           • b. mass of CO2 dissolved in each sample

           • c. amount of beverage in each sample

           • d. independent variable

         • Assuming that all of the experimental data are correct, what is a reasonable conclusion for this experiment?

           • a. Greater amounts of CO2 dissolve in a liquid at lower temperatures.

           • b. The different samples of beverage contained the same amount of CO2 at each temperature.

           • c. The relationship between temperature and solubility seen with solids is the same as the one seen with CO2.

           • d. CO2 dissolves better in a liquid at higher temperatures.

         • The scientific method used by this student showed that:

           • a. the hypothesis is supported by the experimental data.

           • b. the observation accurately describes what occurs in nature.

           • c. the experiment is poorly planned.

           • d. the hypothesis should be thrown out.

         STANDARDIZED TEST PRACTICE CHAPTER 1

         More Than One Graphic

         If a test question has more than one table, graph, diagram, or drawing with it, use them all. If you answer based on just one graphic, you’ve probably missed an important piece of information. For questions 5-7 above, make sure that you accurately analyzed both graphics before answering the questions.