Week 1 - Unit 1.1 - Measurement1 PDF

Unit 1.1 – Measurement BASIC CHEMIST RY – CHAPTER 2  Did You Remember to… ❑ Explore eConestoga and the student portal ❑ Get a locker (through myConestoga) ❑ Upload a picture and pick up your ONE card ❑ Set up your textbook, pick up the program package ❑ Complete the Student Lab Safe...

Unit 1.1 – Measurement BASIC CHEMIST RY – CHAPTER 2  Did You Remember to… ❑ Explore eConestoga and the student portal ❑ Get a locker (through myConestoga) ❑ Upload a picture and pick up your ONE card ❑ Set up your textbook, pick up the program package ❑ Complete the Student Lab Safety quiz (100%) I cannot let you participate in any labs if you are not dressed appropriately, and you have not completed the safety quiz with a score of 100%  What will you REALLY Learn Today? ◦ How to record numbers scientifically ◦ What a measured vs exact number is Unit Outcomes ◦ What a significant figure is and how to 1.1 Write names and abbreviations for metric or SI identify them units used in measurements of length, volume, mass, and temperature. 1.2 Identify a number as either measured or exact. 1.3 Determine the number of significant figures in a Have you ever wondered why we report numbers measured number. the way we do? 1.4 Report measurements using significant figures The temperature outside is 16 °C and appropriate units. (not 16.26598374 °C)  Measurement Every measurement has a number and a unit The number and the unit are generally separated by a space In Canada, we use the metric system of measurement Each type of measurement has a base unit  1. Length In chemistry, length is commonly measured in meters (m), centimeters (cm) or millimeters (mm) 1 m = 100 cm = 1,000 mm The smaller the unit, the bigger the number Which is longer? A. 1 m or 500 mm B. 6 m or 600 cm  2. Volume Volume is the 3-dimensional space occupied by a substance In chemistry, volume is commonly measured in liters (L) or milliliters (mL) 1 L = 1,000 mL A cubic centimeter (cc) has the same volume as a milliliter 1.0 cm3 = 1.0 cc = 1.0 mL Which is a greater volume? A. 1 L or 750 mL B. 1 mL or 1 cc  3. Mass Mass is a measure of the quantity of material something contains It is measured in the lab using an electronic balance In chemistry, mass is commonly In healthcare, mass is commonly measured in grams (g) or measured in pounds (lbs) or milligrams (mg) kilograms (kg) 1 g = 1,000 mg 1 kg = 2.205 lbs Which is heavier? A. 1 g or 100 mg B. 1 kg or 1 lb  You tell Me For each of the following, indicate whether the unit describes (1) length, (2) mass, or (3) volume. A. A person is 2.0 m tall B. A medication contains 250 mg of Cefalexin C. A bottle contains 1.5 L of water U.S. System of Measurement  Measured vs. Exact Measured numbers are reported using a measurement tool (ex. a ruler) and always contain some degree of uncertainty 4.4 cm? 4.5 cm? 4.45 cm? Exact numbers are either obtained by counting items or they are definitions that compare two units in the same measuring system 2 baseballs 1 kg = 2.205 lbs  You Tell Me – Measured or Exact Identify the following values as either measured or exact *Hint - ask yourself: “was this measured with an instrument or is it just a given?” (A) there are 100 cm in 1 m (B) my finger is 8.3 cm long (C) the average mass of a mid-size car is 3,497 pounds (D) there are 70 people in the class  Measured Numbers In the lab we will take numerous measurements, each with different degrees of uncertainty So how do we know what to report? The number we report is based on the precision of the instrument used to measure it Let’s start with length: 1. observe the numerical values of the marked lines (what you know) 2. estimate the last digit by visually dividing the space between the smallest marked lines This estimated number is the last number reported for a measured number  You Tell Me - Length Measure the length of the objects in each diagram using the metric ruler in the figure Don’t forget to report what you can see (measured) + one guessed number (estimated digit)  In the Lab – Mass and Temperature 1. Mass (g) ◦ on an electronic balance, the last number will fluctuate ◦ we report all numbers displayed (last number is estimate) 2. Temperature (°C) ◦ the increments on a thermometer display up to the ones What number would you ◦ we report temperature to one decimal place (estimated record? digit) 61.6°C °C °C  In the Lab - Volume 3. Volume (mL) ◦ the surface of the liquid will make a U-shape called a meniscus ◦ we record the volume at the bottom of the meniscus ◦ the estimated digit will vary based on the glassware used to measure 36.9 mL 44 mL A graduated A beaker cylinder  You Tell Me – Digits and Units Report the following measurements to the correct number of digits and units mL mL  Significant Figures In a measured number, the significant figures (SFs or sig figs) are all of the digits, including the estimated digit All nonzero numbers are counted as significant figures Measurement Number of Sig Figs 38.15 cm 4 5.6 ft 65.6 lbs Zeros may or may not be significant, depending on the position in the number…  Significant Zeros Zeros between nonzero digits are significant Measurement Number of Significant Figures 50.8 km 3 2,001 mins 702 lbs Zeros at the end of decimal numbers are significant Measurement Number of Significant Figures 1.0 mL 2 5.11700 mins 180.00 lbs  NOT Significant Zeros Zeros at the beginning of decimal numbers are not significant Measurement Number of Significant Figures 0.442 km 3 0.022 g 0.00361 lbs Zeros at the end of nondecimal numbers are not significant Measurement Number of Significant Figures 44 000 km 2 810 cm 6 150 000 g Summary of Rules (pg. 31)  You Tell Me – Number of Sig. Figs. State the number of significant figures in each of the following measurements A) 0.030 m B) 4.050 L C) 0.0008 g D) 2.80 m E) 450,000 cm  Exact Numbers Exact numbers: o are not measured (no balance, no stopwatch, nothing) o have an infinite number of significant figures (∞) o do not affect the number of significant figures in a calculations… How many sig figs?  You Tell Me – Significant Figures State the number of significant figures in each of the following measurements A) there are 60 s in 1 min B) 0.0902030 kg C) 30,100 in D) 10 beakers  Summary 1.1 Write names and abbreviations for metric or SI units used in measurements of length, volume, mass, and temperature. 1.2 Identify a number as either measured or exact. 1.3 Determine the number of significant figures in a measured number. 1.4 Report measurements using significant figures and appropriate units.  Reference Unless otherwise specified, all images were obtained with permission from Pearson Education Inc. Timberlake & Timberlake. Basic Chemistry (6th). Pearson (2020).