Chapter 1 Introduction to Science / Safety

Transcription

1 Chapter 1 Introduction to Science / Safety In this year you shall learn chem, So that you won t be one of them, You ll say chemistry really matters To your teacher not just to flatter. It might be hard but please don t run, Cause chemistry is super fun, Just come to class, And know your math, And you will learn quite fast. - Ben Nichols Learning Targets: Students should be able to identify and use glassware properly in the lab. Students should be able to read a Safety Data Sheet (SDS) to determine the proper procedures for handling, storing, and disposing of chemicals. Students should be able to safely and effectively use a Bunsen Burner. Students should know and follow proper safety precautions in the lab. Students should be able to locate and properly use safety equipment in the lab. Students should be able to make qualitative and quantitative observations. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 1

2 What is science? What is chemistry? Branches of Chemistry There are at least 25 specialty areas of chemistry, but each one can be classified under one of the following six major divisions or branches of chemistry: 1. Organic chemistry: the study of most carbon-containing substance Example: 2. Inorganic chemistry: the study of all substances not classified as organic, mainly those that do not contain carbon Example: 3. Analytical chemistry: the study of the identification of the components and composition of materials Example: 4. Physical chemistry: the study of the properties, changes, and relationships between energy and matter at the atomic scale Example: 5. Biochemistry: the study of substances and processes occurring in living things Example: 6. Theoretical chemistry: use of math and computers to understand chemical behaviors and design new compounds Example: Obviously, these divisions will often overlap Types of Research 1. Basic research is done to increase knowledge Example: Examine all the reactions involving water 2. Applied research is done to solve a problem Example: Investigate the side effects to a new drug 3. Technological development is done to improve quality of life Not research itself, but, rather, the outcome of research Often lags behind the basic research done on the same substance Example: The creation of a renewable fuel source for home heating Technology is the application of knowledge (usually scientific) for practical purposes. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 2

3 Model - commonly used to help visualize atoms and molecules. Chemists models of atoms and molecules are much larger than the real thing. Models can be mathematical or even imaginary. Qualitative and Quantitative observations Inference and Observation Variables The scientific method often employs the use of variables to carry out a particular study. There are two types of variables: The independent variable is the variable that is being manipulated (changed) in the procedure. (The cause) The dependent variable is the variable (thing) that is being affected by the manipulation of the independent variable (The effect) A control (trial) is often used as a comparison to the independent variable. This serves as the normal situation for a given sample or situation. NOTE: When describing variables, it is important to be specific. For example, if the amount of water is changed, the independent variable is mass of water or volume of water. If the color of water is changed, the independent variable would be color of water, etc. Example: Enrique and Lacey are testing soil for contamination outside a nuclear power plant. They test the concentrations of contaminants at different distances from the plant. 1. What is the independent variable? 2. What is the dependent variable? 3. What are some factors that Enrique and Lacey will keep constant? Honors Chemistry Chapter 1 Intro/Safety/Elements Page 3

4 Graphing and Data Analysis Graphs are a useful tool for displaying scientific data because they show relationships among variables in a compact, visual form. You may have used x-y graphs, or Cartesian graphs, in your math classes. Below are the four basic steps to constructing a graph from data in the chemistry lab. 1. Determining the variable In an experiment, the independent variable is the property that is under control and can be varied. The dependent variable is the property that is measured, observed, counted, or found. The independent variable is usually, but not always, assigned to be the x value, and the dependent variable is usually assigned to be the y value. If the study involves a measurement as a function of time, time is plotted on the x axis. 2. Scaling the axes The scale of the axes includes all data points and allows as much room as possible on both axes. Each axis should be evenly divided with plenty of space between divisions, making the graph easy to read and understand. The divisions should be labeled in multiple units of (i.e. 1, 2, 5, 10, etc.). Each axis should also be labeled with a description of what it represents and the units of measurement. 3. Plotting the data If the plotted data points roughly form a straight line, use a transparent ruler to draw a line that best represents the data points. This is known as the best-fit line. If the points do not form a straight line but appear to form a curve, lightly sketch the curve with a pencil, connecting all the data points. 4. Titling your graph It is important to add a title to the top of your graph, so that anyone looking at the graph can easily identify its purpose. Most of the time the title of the graph is y vs. x. Example: Your school is putting on a play. To raise money for the event, tickets for the play are being sold for $3.00 each. The chart below shows how much money will be made from selling certain numbers of tickets. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 4

5 Graphs show the relationship between x and y variables. If data forms a straight line when plotted, then x and y have a linear relationship. This line can be described by the general mathematical equation y = mx + b where m is the slope of the line and b is a constant. Linear data is said to be directly proportional when dividing one variable by the other gives a constant value. This means that as one variable changes, the other changes at the same rate Not all data forms a straight line when graphed; your graph may show a curve. If the curve drops as you move from left to right, and dividing one variable by the other gives a constant reciprocal value, then your graph has an inverse relationship. Quite often, you will need to determine whether or not a graph expresses a linear relationship. To do this you must draw what is known as a "best fit" straight line, also called a "regression line". The purpose of the graph is to visually display relationships which may not be apparent from data tables. Experimental errors which are always present may obscure the relationships. The best fit line averages out the errors. Without computer software, you will need to draw the lines "by hand" and then make a judgment about whether the points are "linear". Remember, sometimes a graph represents neither a direct nor an inverse of relationship, but, rather, simply traces the effect of x on y. Many types of graphs exist: line graphs, bar graphs, pie charts, histograms, etc. In order to display the results of the experiment appropriately, the right type of graph should be used. A line graph is used when the independent variable changes in regular increments and must be placed in a specific order. Points are plotted and then connected. A bar graph is used when the independent variables can be placed in any order. A histogram is a type of bar graph used when the data involves the frequency of occurrence. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 5

6 Worksheet 1 1. A new drug is suspected to reduce the number of malignant tumors in patients diagnosed with cancer. Dr. DeJesus gives his patients different doses of the medication. a. What is the independent variable? b. What is the dependent variable? c. What are some factors Dr. DeJesus is likely to keep constant (as control variables)? d. What could Dr. DeJesus do as a control trial and why would this experiment benefit from it? 2. Mira is measuring the boiling point of 5 different substances. What type of graph would be best to show the results of the experiment? 3. Jorge is measuring the ph of a sample for every 10 ml of water added. What type of graph would be best to show the results of the experiment? 4. The concentration of lead (in parts per billion) was tested in a local water system every morning for 2 weeks. The results from day1-day14 were 20 ppb, 21 ppb, 23 ppb, 21 ppb, 45 ppb, 43 ppb, 38 ppb, 35 ppb, 35 ppb, 32 ppb, 30 ppb, 28 ppb, 27 ppb, and 27 ppb. a. What is the independent variable? b. What is the dependent variable? c. In the space below, use a ruler to construct a data table for the results in the description above. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 6

7 d. Using the grid below, construct a graph for the data in the table you just constructed. No best fit line needed. 5. The length of six different objects was measured in both centimeters and inches. The data was recorded in the table to the right. a. Plot the length in centimeters vs. the length in inches using the provided coordinate axes below. Label both axes. Object Length Length (cm) (in) b. Draw a best fit line. Based on your analysis of the data, if a measurement of 5.00 cm was made, how many inches long would the object be? c. Calculate the slope of the best fit line. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 7

8 Worksheet 2 Answer the questions about the following lab scenario. Problem Statement: The purpose of this lab is to determine the number of molecules contained in a sip of water. Materials: Dry plastic cup, tap water, balance Procedure: One dry plastic cup was obtained. The plastic cup was massed on the balance and the mass in grams was recorded. The cup was filled with water from the water fountain. The mass (in grams) of the cup and water together was determined and recorded. A sip was taken from the cup. The mass (in grams) of the cup and water (after sipping) was determined and recorded. Data Obtained: Questions: Item Mass (g) Plastic Cup 4.21 Plastic cup with water Plastic cup with water after sip was taken For this experiment, list the dependent and independent variables. Independent variable: Dependent variable: 2. Determine the mass of water in the cup. 3. Determine the mass of your sip of water. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 8

9 Worksheet 3 1. Select the most appropriate branch of chemistry from the following choices to best describe each of the investigations: organic chemistry, analytical chemistry, biochemistry, theoretical chemistry. a. A forensic scientist uses chemistry to find information at the scene of a crime. b. A scientist uses a computer model to see how an enzyme will function. c. A professor explores the reactions that take place in a human liver. d. An oil company scientist tries to design a better gasoline. e. An anthropologist tries to find out the nature of a substance in a mummy s wrap. f. A pharmaceutical company examines the protein on the coating of a virus. 2. For each of the following types of chemical investigations, determine whether the investigation is: basic research, applied research, or technological development. a. A laboratory in a major university surveys all the reactions involving bromine. b. A pharmaceutical company explores a disease in order to produce a better medicine. c. A scientist investigates the cause of the ozone hole. d. A chemical company develops a new biodegradable plastic. e. A laboratory explores the use of ozone to inactivate bacteria in a drinking-water system. Honors Chemistry Chapter 1 Intro/Safety/Elements Page 9

10 Accident At Jefferson High Video 1. Be and proceed with. 2. Tie back long. 3. Roll up long. 4. Remove loose and dangling. 5. Never wear or open toed shoes. 6. Wearing an can protect you skin and clothes. 7. Splash proof are always a must! 8. When diluting acids, add to in order to avoid splashing. 9. Rinse with water after use, and before placing them on the table. 10. Never put anything in your or touch chemicals with your hands. 11. Double check before using chemicals. 12. Use bases, like sodium bicarbonate, to clean up spilled. 13. Use acids, like vinegar, to clean up spilled. 14. Use plenty of if you spill chemicals on your skin. 15. If anything gets in your eyes, rinse for minutes. 16. Never dump chemicals in the or the wastebasket unless instructed by your teacher. 17. When lighting a Bunsen burner, always light the match turning on the gas. 18. Never throw a into a wastebasket or sink. Put in the proper container. 19. True or False: You can tell if glassware is hot by looking at it. 20. To tell if glassware is hot, use. 21. When heating a over a flame, always point away from you and keep it moving. 22. True or False: If a fire starts, you should douse it with water. 23. If a person catches on fire, use the. Bunsen Burner Safety Honors Chemistry Chapter 1 Intro/Safety/Elements Page 10

11 SDS SAFETY LAB A safety data sheet (SDS) is designed to provide procedures for handling or working with a particular substance. SDS s include information such as physical data (melting point, boiling point, flash point, etc ), toxicity, health effects, first aid reactivity, storage, disposal, protective equipment, and spill/leak procedures. These are of particular use if a spill or other accident occurs. Prelab: define the following terms (look them up online or in a book.) Asphyxiant Corrosive Flash point Irritant Mutagen Oxidizer Stability Reactivity Combustible Explosive Flammable Hemolytic Volatile ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Lab Questions 1. Read the label on the bottle marked hexane at station 1. What is the flashpoint? What will acute exposure cause? What will chronic exposure cause? 2. List the chemicals at station 2. List the name of one substance that is a strong oxidizer? List the name of one substance that is irritating to the skin? List the name of one substance that is mutagenic? Honors Chemistry Chapter 1 Intro/Safety/Elements Page 11

12 3. At station 3, put a piece of zinc in a test tube. Add a few drops of hydrochloric acid. Put a piece of aluminum in another test tube. Add a few drops of hydrochloric acid. Which metal would you describe as reactive? Which one is more stable? Clean up by throwing the extra metals (with the solution) in the trash. Rinse the test tubes and place them upside down in the test tube rack. 4. Sodium hydroxide is a strong base. At station 4, place a small amount of egg white in plate well. Put a few drops of the diluted sodium hydroxide solution on some egg whites. Stir. (Your eyes are made up of substances similar to egg whites. This demonstrates what would happen if you were to get a base in your eyes.) Write down your observations. Clean up by throwing the egg whites in the trash then rinse the cell well. 5. At station 5, place one drop of acetone and one drop of water on the lab table at the same time. Do not mix the drops together. Which one is more volatile? 6. Your instructor will do a demonstration for you. Please write down your observations. 7. Scavenger Hunt: Find the following equipment and fill in the following table. Equipment Name Location in Laboratory How is this equipment used? Fire Extinguisher Laboratory Apron Safety Shower Broken Glass Disposal Fire Blanket Eye Wash First Aid Kit Honors Chemistry Chapter 1 Intro/Safety/Elements Page 12