INTRODUCTION: Chemistry is a quantitative science. We measure specific amounts of grams of chemicals to react with other chemicals. We measure temperature, volume, pressure and changes in mass. All these measurements require numbers and units. Measurements also give us limited information. The amount of information we learn from measurements is related to the precision of the instrument that we use. This information is called significant figures. One quantity that we will measure indirectly is especially important and unique to Chemistry; this is the “mole”. The mole is a means of counting. Atoms are far too small to individually count, so we count atoms, molecules and compounds in larger groups. Just like we count larger amounts of eggs in dozens or gross, we count chemical particles in “moles” in order to allow us to work with measurable quantities of chemicals. When chemicals react they react in a whole number ratio, which is related to the number of moles. However, we measure reactants and products in a chemical reaction in terms of mass in grams. In this unit we will learn how read measurements, determine the amount of information in the measurement and then convert the measurement into other chemical quantities. It is time to start your problem solving, calculating engines!
OBJECTIVES: As you study this unit, you should be able to do the following:
Rewrite measurements in scientific notation and do mathematical operations with numbers in exponential notation. (3.1 and GIA)
Distinguish between the accuracy and precision and error of a measurement. (3.1)
Determine the number of significant figures in a measurement and in a calculated answer. (3.1, activity)
Convert between equivalent measurements using constructed conversion factors. (3.2 and GIAs)
Solve problems by breaking them down into steps and applying dimensional analysis. (3.3)
Calculate the density of material from experimental data. (3.4 and GIAs)
Define a “mole” and relate it to Avogadro’s number. (10.1)
Define molar mass and tell how it relates to the mass of a substance. (10.1)
Convert among a number of particles, moles and mass of a substance. (10.1)
Convert moles to volume and volume to moles, using the volume of one mole of a gas at STP (22.4 L). (10.2)
Calculate the percent composition of a substance from its chemical formula or experimental data. (10.3)
Derive the empirical and/or molecular formula of a compound from experimental data. (10.3 and lab)
LEARNING ACTIVITIES:
To learn about objectives 1-6:
READ Ch. 3, pp. 62-93
WRITE “Exponential Notation” worksheet.
COMPLETE “Internet Activity on Significant Figures”
MEMORIZE the meaning of the various prefixes on Table 3.2, p. 74.
WRITE GIA 5-2: Problem Solving Using Conversions and Dimensional Analysis.
WRITE out answers to the following questions at the end of Chapter 3: 57, 58, 60, 64, 70-73, 76, 84, 86, 91 on pp. 96-97
TEST YOURSELF with the Chapter 3 Self-Test questions.
To learn about objectives 7-12:
READ Chapter 10, pp. 287-312. See objectives for specific section.
READ and PERFORM lab “Molar Quantities: Weighing as a Means of Counting”.
READ and PERFORM Lab, “Determining the Formula of a Hydrate.”
WRITE out answers to the following questions at the end of Chapter 10: 49, 50, 51, 58, 60, 61, 63 (a) and (d), 64 (a) and (d), 66, 67, 69, 75 (b) on pp. 315-316.
To make sure you understand the objectives for this unit:
ASK me, the teacher, any lingering QUESTIONS
TAKE the Unit’s Self-Test
Schedule:
QUIZ on chapter 3, Day 3 of week of
Dec. 3rd, 2007. Chapter 3 homework due same day.
TEST on Unit 5 (Chapters 3 and 10) on
Day 4 of week of Dec. 10. Chapter 10 homework due same day.
