advertisement

Name _____________________________ Notes – Chapter 2: Measurements and Calculations Units of Measure SI Units – International ____________________________________ Quantity (what we measure) Base Unit Volume …………………………………………………………………………. _________________ Distance………………………………………………………………………… _________________ Time……………………………………………………………………………… _________________ ___________..................................................................... Grams (g) Temperature…………………………………………………………………. _________________ Amount of substance……………………………………………………. _________________ Metric Line (back of Periodic Table) Prefix Kilo- Hecto- Deca- BASE Deci- Centi- Milli- Conversion Factor Conversion Factor as a ratio Conversions Ex. How many milliliters (mL) are in 2 liters (L) of water? Step 1: Identify what you are given (you need to include the number, the unit, and the substance) and what you are for. asked Step 2: Set up a T-Chart with the given at the beginning. Step 3: Use the metric line (or other conversions) to fill in conversion factors until you get the units you need (make sure units cancel). Step 4: Multiply everything on the top and divide anything on the bottom. T-Chart = 1. If you are 1.5 meters (m) tall, what is your height in millimeters (mL)? 2. A marathon is about 42 kilometers (km) long. How many meters are run during the race? 3. A normal piece of paper is about 28 centimeters (cm) long. How many meters is this? all other Accuracy – Precision – Percent Error (% error) compares the experimental value to the ____________ value (This means it is a measure of ____________). Accepted value – Experimental value – Formula: Ex. Chemistry students measured the mass of a sample to be 25 grams (g). If the sample actually has a mass of 23.2 g, what is the students’ percent error? Scientific Notation 1. _______________________________ 2. _______________________________ 3. _______________________________ Scientific notation helps us write very _________ and very __________ numbers a lot more easily and quickly. Instead of 1,000,000 we write… The first number can have only _____ digit before the decimal point. 1.0 x 106 The exponent tells us how many decimal places the decimal moved. Convert each number to scientific notation Convert to standard notation 1) 143,000 4) 1.7 x 103 = _________________ -2 = __________________ 2) 13,100,000 = _________________ 5) 4.03 x 10 = __________________ 3) 0.00325 = _________________ 6) 9.0 x 105 = __________________ Significant Figures (Sig Figs) How many significant figures are there in a number? Rule 1: _________________ digits are always significant (Ex. 9, 4, or 8) Rule 2: If a zero is _________________ by significant digits, it is also significant (Ex. 5,002) Rule 3: Final or trailing zeros are only significant if they follow a decimal number (Ex. 0.050 only the five and the zero after it are significant) How many significant figures are in… 1) 13,951 ____ 2) 402 ____ 3) 0.000230 _____ 4) 20.10 _____ When you multiply/divide or add/subtract, the number of significant figures change. When you multiply or divide, the answer will have the same number of significant figures as one with _________ sig figs. o Ex. 1 2.0 x 16.01 = o Ex. 2 A student works for $8/hour. If they guess they worked about 8 hours this week, estimate (using significant figures) how much they will earn. When you add or subtract, the answer will have the same number of decimal places as the one with _________ decimal places. o Ex. 1 1.27 + 0.02003 = o Ex. 2 6.0087 – 3.24 = Density Formula: 1. What is the density of an object that has a mass of 2.5 grams and a volume of 25 mL? 2. A student finds an interesting solid substance. The student finds the mass is 13.2 grams and the volume is 19 mL. What is the density of the unknown substance? 3. What is the density of aluminum if a 10 mL block has a mass of 27.3 grams? 4. What is the volume of a piece of copper that has a mass of 6.5 grams and a density of 8.92 g/cm 3? 5. You pour 100 mL of water into a beaker. If you know the density of the water is 1.00 g/mL, what mass of water do you have?