What is Chemistry? Chemistry: 5 areas of Chemistry: o Organic- o Inorganic- o Biochemistry- o Analytical- o Physical- Chapter 1 and 3 Guided Notes Scientific Method: 1. 2. 3. 4. 5. Variables: -The variable that is changed in the experiment. -The variable that changes due to the change made in the experiment. Scientific measurement Types of measurement Quantitative- Qualitative- 4 feet extra large Hot 100ºF How good are the measurements? Scientists use two word to describe how good the measurements are - how close the measurement is to the actual value - how well can the measurement be repeated To evaluate: Accuracy: Precision: Error: - The correct value based on reliable references. - The value measure in the lab. Error - The difference between the two values. Example Problem: What is the % error of a measured value of 114 lb if the person s actual weight is 107 lb? Scientific Notation -A given number is written as the product of two numbers: a coefficient and 10 raised to a power. For example, the number 102, 300 is written as 1.023 x 10 5. -In scientific notation, the coefficient is always a number equal to or greater than one and less than ten.
Common Types of Laboratory Equipment Used to Measure Liquid Volume Uncertainty in Measurement A digit that must be is called. A always has some degree of uncertainty. Significant Figures Indicate precision of a measurement. Recording Sig Figs Sig figs in a measurement include the known digits plus a final estimated digit Significant Figures Practice How many significant figures are in each of the following? a. 100 b. 1.0 x 10 2 c. 1.00 x 10 3 d. 100. e. 0.0048 f. 0.00480 Significant Figures in Calculations Addition and Subtraction: The term with the least number of decimal places ( least accurate measurement) determines the number of significant figures in the answer. Rules for Counting Significant Figures Overview 1. Nonzero integers 2. Zeros leading zeros captive zeros trailing zeros 3. Exact numbers Why is being able to locate, and count significant figures an important skill? 12.52 +349.0 + 8.24 369.76= 369.8 meters Multiplying and Dividing: The term with the least number of significant figures ( least accurate measurement) determines the number of significant figures in the answer. 7.55m x 0.34 m = 2.6m 2
Use scientific notation to express the number 480 to: a. One sf b. Two sf c. Three sf d. Four sf Rounding Rules look at the number behind the one you re rounding. If it is 0 to 4 don t change it If it is 5 to 9 make it one bigger round 45.462 to four sig figs to three sig figs to two sig figs to one sig fig Perform each of the mathematical operations, and express each result to the correct number of sf. a. 97.381 + 4.2502 + 0.99195 b. 171.5 + 72.915-8.23 c. 1.00914 + 0.87104 + 1.2012 d. 0.102 x 0.0821 x 273 1.01 e. 2.00 x 10 6 3.00 x 10-7 International System (le Système International) The Fundamental SI Units Physical quantity Name Abbreviation Length Mass Temperature Time Amount of substance Electric current meter Kilogram Kelvin second mole Ampere Dimensional Analysis Dimensional analysis (DA): a method used to from unit of measure to another. a The Factor-Label Method Ø DA is used when converting from one unit of measure to a different unit of measure so a must be used. Conversion factor: a of equivalent measurements. Example: 1000 mg = 1 g 1 min = 60 s
Because the conversion factors are equal to, they can be multiplied by other factors without changing the size of the quantity measured. Steps for conversions: 1. Identify & units. 2. Line up conversion factors so units. 3. Multiply all top numbers & divide by each bottom number. 4. Check units & answer. ALWAYS include the units!! Example Problems: One Step 1. What is the mass in grams of 64.9 mg? 2. What is the length in centimeters of 8.654 m? 3. Your European hairdresser wants to cut your hair 8.0 cm shorter. How many inches will he be cutting off? Example Problems: Multi-Step 4. How many cm are in 3.1 km? 5. How many milliliters are in 1.00 quart of milk? (1 L = 1.057 qt) 5. How many meters are in 3.3 inches? Example Problems: Compound 7. How many mph are in 4.55 m/s? 8. How many g/in are in 0.21 kg/ft?
Temperature Three Scales Notice a degree C = a degree K 9 F T F = T C x + 32ºF 5 C T K = T C + 273 K T C = T K - 273ºC Practice Problem 1 Temperature Conversions I Normal body temperature is 98.6 F. Convert this temperature to the Celsius and Kelvin scales. 98.6 F = 37.0 C 98.6 F = 310.2 K Practice Problem 2 Temperature Conversions II Water boils at 100 C. What is the boiling point of water on the Fahrenheit scale and Kelvin scale? Practice Problem 3 Temperature Conversions III Liquid nitrogen, which is often used as a coolant for low-temperature experiments, has a boiling point of 77 K. What is this temperature on the Fahrenheit scale? T F = -281 F - 40 T F = -321 F
Density mass Density = volume Often expressed in or Is an property that depends only on the composition of a substance, not on the size of the sample. 1. A 1.1-gram ice cube raises the level of water in a 10 ml graduated cylinder 1.2 ml. What is the density of the ice cube? 2. Suppose you dropped a gold cube into a 10 ml graduated cylinder containing 8.50 ml of water. The level of the water rises to 10.70 ml. You know that gold has a density of 19.3 g/cm 3. What is the mass of the gold cube? 3. A chemist, trying to identify the main component of a compact disc cleaning fluid, finds that 25.00 cm 3 of the substance has a mass of 19.625 g at 20 C. The following are the names and densities of the compounds that might be the main component. Compound Density in g / cm 3 at 20 C Chloroform 1.492 Diethyl ether 0.714 Ethanol 0.789 Isopropyl alcohol 0.785 Toluene 0.867 Which of these compounds is the most likely to be the main component of the compact disc cleaner? Density = 0.7850 g / cm 3