CHAPTER 1 ADAPTED FROM CHEMISTRY BY OPENSTAX. LICENSED UNDER CREATIVE COMMONS ATTRIBUTION LICENSE 4.0 PRE-LECTURE READING QUESTIONS: Pre-lecture reading questions will show up here for future chapters. Chapter 1.1: Chemistry in Context What is chemistry? Chemistry is the study of: CLASS ACTIVITY: Chemistry is the central science! Create a concept map of different concepts that connect to chemistry. How do we view chemistry? Macroscopic view Microscopic view Symbolic (or formulaic) view 1 Chapter 1.2: Phases and Classification of Matter Matter is anything that has mass and takes up space (i.e. has volume) There are three common phases (sometimes called “states”) of matter: ____________ are the building blocks of matter. Atoms combine together by strong chemical bonds to form molecules. Multiple atoms of the same element can combine to form molecules, or atoms from multiple elements can combine to form compounds. CLASSIFYING MATTER In order to better understand matter, and its properties, we must classify matter. SM ALL GROUP DISCUSSION: LOOK AT THE PICTURES BELOW AND DISCUSS A NY DIFFERENCES BETWEEN THE TWO WITH THE CLASSMATES SITTING AROUND YOU. 2 CLASSIFICATION SCHEME: Chapter 1.3: Physical and Chemical Properties Properties of matter is what allows us to distinguish one substance from another. There are two types of properties: PHYSICAL and CHEMICAL. A physical property is a characteristic of matter that is NOT associated with a change in its chemical composition. Some physical properties are: A chemical property is a characteristic when the matter is changed from one type of matter to another. Some chemical properties are: Some physical properties can only be observed when the matter undergoes a physical change. A physical change is a change in state of properties of matter without an accompanying change in the chemical composition. Another way to say this: a physical change is one in which the chemical composition is the same at the beginning and the end of the change. Some examples of physical changes are: 3 4 Chemical changes produce one or more types of matter that differ from the matter present from before the change. Some examples of chemical changes are: All properties of matter fall into one of two categories: _____________________________ - depend on the amount of substance present Examples are: _____________________________ - does not depend on the amount of substance present Examples are: GR OUP AC TIVITY: For the following changes, state whether the change is physical or chemical. Gasoline evaporating after being spilled A match igniting a firework Copper that has turned green Digesting meat (or vegetables!) A passing train that flattens a penny Sugar dissolves in coffee Ice melting into liquid water Copper reacting with nitric acid Chapter 1.4: Measurements CL ASS DI SCUSSION: What meaning does the following number have? International System of Units (SI Units) – an internationally agreed upon system of units for measurements and are used by the United States National Institute of Standards (NIST) since 1964 (even though most of the United States refuses to use SI units like the rest of the world!) READ ABOUT THE DIFFERENT BASE UNITS IN YOUR TEXTBOOK Every single number MUST have a unit associated with it. Without units, numbers are meaningless in chemistry! 5 Base Units: These are units that all other units can be derived from! Fill in this table with the SI unit for each property. Table 1.2 : SI base units Property Name of Unit Symbol of Unit ampere A candela cd Length Mass Time Temperature Electric current Amount of substance Luminous Intensity Sometimes, numbers are too big or too small to use just the base unit, so we can use a prefix to the base unit to indicate fractions or multiples of the SI unit. Below is a table describing common unit prefixes. Prefix Symbol Factor femto f 10-15 pico p 10-12 nano n 10-9 micro µ 10-6 milli m 10-3 centi c 10-2 deci d 10-1 kilo k 103 mega M 106 giga G 109 tera T 1012 GR OUP AC TIVITY: Complete the following equivalencies; the first one is completed for you. 1000 meters = 1 meter = 1 kilometers ________ kilometers 1 micrometer = ________ meters 1 kilogram = ________ milligrams 106 µL = ________ liters 150 mL = ________ liters 6 Derived Units Using the seven SI base units, we can derive many other units. Volume is a derived unit, that is derived from length. Density is also a derived unit – it is the ratio of mass per unit volume. Chapter 1.5: Measurement Uncertainty, Accuracy, and Precision Exact numbers, such as those when counting, do not have any uncertainty in their measurement. 1 dozen eggs = 12 eggs 1 foot = 12 inches 1 inch = 2.54 centimeters (exactly) These are all exact quantities, there is no ambiguity in how certain we are of those numbers. HOWEVER, some measurements only contain some degree of certainty. There are rules for reporting the certainty in your measurement. CLASS AC TIVITY: Answer the following questions about the graduated cylinder shown. What are you sure about the volume of the water? In order to be as accurate as possible with your measurement, what must you do to your reading? 7 Therefore, every measurement has some uncertainty!!! All digits reported in a measurement, including the uncertain last digit, are called significant figures. There are rules for looking at a number and determining which digits are significant and which are not. When manipulating numbers (using addition/subtraction or multiplication/division), significant figures play an important role, as you do not want to overstate your certainty in calculated numbers. This is where rounding will come into play. Significant Figures – Rules and Manipulations SIGNIFICANT FIGURES RULES 1. All nonzero digits are significant 2. Zeros between two significant figures are significant also (these are called captive zeros). 3. Leading zeros (zeros at the beginning of a number) are NEVER significant 4. Trailing zeros (zeros at the end of a number) are ONLY significant if a decimal place is written in the number (trailing zeros in scientific notation are always significant because scientific notation uses a decimal place). CLASS AC TIVITY: Examples and Practice: 2030 m 2030.5 mg 0.006 mL 0.0060 cm 0300 g 100,000 km 0.0506 cm 0.05060 kg MANIPULATIONS, ROUNDING, AND SIGNIFICANT FIGURES RULES 1. If adding or subtracting, round the result to the same number of decimal places as the number with the least number of decimal places. Ex: 14.578 m + 06.9__.m 2. If multiplying or dividing, round the result to the same number of digits as the number with the least number of significant figures. Ex: 657 m x 34 m = Accuracy and Precision To be good chemists, we often make repeated measurements or run multiple trials to ensure the quality of our findings. These multiple measurements/trials, help us know the precision and accuracy of our measurements. ACCURACY: 8 PRECISION: 9 GROUP ACTIVITY: The image below shows three different examples of a group of three arrows (“measurements”) shot at a target with a bull’s eye (“true value). In small groups with the classmates around you, label the following sets of arrow shots as “accurate and precise,” “precise but not accurate,” “neither accurate nor precise.” Scientific Notation Some numbers are too big for us to write or type out the entire number. For example, the mass of an electron is: 0.000 000 000 000 000 000 000 000 000 000 91 kg This number is much easier to write in scientific notation. Scientific notation is written so that a number between 1 and 10 is written with a “x 10x” with the x exponent being a whole number that represents how many spaces the decimal was moved to make a number between 1 and 10. • if the number is small ( <1 ), then you would move the decimal place to the right and get a negative exponent • if the number is large ( >1), then you would move the decimal place to the left and get a positive exponent. For the mass of an electron: Chapter 1.6: Dimensional Analysis Imagine measuring the speed of an athlete running. If you do not have a radar speed gun, you could measure both the length the runner runs and the time it takes the runner to run that length, since speed is a derived value: distance (or length) speed = time If a runner runs 100 m in 10 s: Often, we must calculate our value of interest from other measurements. If this is the case, we will use dimensional analysis to calculate or manipulate our values. Unit factors are made from equalities and are a ratio of two equivalent quantities with different units. 10 There are two unit factors we can write from the following equality: 1 inch = 2.54 centimeters We can then use these unit factors to do conversions. CLASS ACTIVITY: Convert the following measurements. 86.7 cm to inches 43 mL to in3 (this is tricky – multiple operations must be used!) GR OUP AC TIVITY: C onvert the following measurements in small groups. 34.8 in to cm 79 in3 to cm3 END OF CHAPTER 1 IN DEPENDENT SUMMARY – S UMMARIZE T HE IMPORTANT A SPECTS O F THE C HAPTER IN YOUR OWN WORDS ALSO: WRITE DOWN A NY Q UESTIONS YOU M AY H AVE STILL HAVE A BOUT THE CHAPTER TO ASK T HE INSTRUCTOR OR T UTORS! 11
