Chapter 7: Chemical Composition Date:____________ Section 1: Measuring Matter - Notes Objectives: Explain how a mole is used to indirectly count the number of particles of matter. Relate the mole to a common everyday counting unit. Convert between moles and number of representative particles. Counting Particles: Chemists need a convenient method for accurately _____________________ the number of atoms, molecules, or formula units of a substance. The ______________ is the SI base unit used to measure the amount of a substance. 1 mole is the amount of atoms in 12 g of pure carbon-12, or ___________________________ representative particles o ________________________________________________________________________ The number is called _____________________________ number. This relationship allows us to ______________________________ by _____________________ them. Converting Between Moles and Particles: Moles to particles: o Example: How many atoms are in 3.50 mol of He? Particles to moles: o Example: If there are 1.1 x 1022 Ag atoms, how many moles of Ag are there? Practice: Calculate the number of molecules in 11.5 mol of water. How many moles are in 5.75 x 1024 atoms of aluminum? How many molecules of AgNO3 are there in 3.25 mol of AgNO3? How many atoms are there?