Presentation on theme: "Density Density is the amount of matter present in a given volume of substance – Formula & units: m d ΔVΔV Mass in grams (g) Density in grams per cubic."— Presentation transcript:
Density Density is the amount of matter present in a given volume of substance – Formula & units: m d ΔVΔV Mass in grams (g) Density in grams per cubic centimeter (g/cm 3 ) or milliliters (mL) Change in Volume in cubic centimeters (cm 3 ) or milliliters (mL)
2 items have to be determined: 1. Mass 2. Volume Determining Mass – Triple Beam Balance
– Balance Rules 1. Always check to see that the balance is leveled and zeroed before using it – Use the adjustment knob 2. Never weigh directly on the balance pan – Always use a weighing boat / paper to protect it 3. Do not weigh excessively hot or cold objects – Why? 4. Clean up any spills around the balance immediately
– Balance Procedures 1. Set the balance to zero 2. Determine the mass (g) by reading the riders at eye level 3. Move the riders along the beam (starting with the largest) until the pointer is at the zero mark
Determining Volume – 2 ways 1. Displacement via a graduated cylinder Procedures A. Try to avoid parallax errors »A»Arise when a meniscus is viewed from an angle rather than at eye level CorrectIncorrect
B. The glass cylinder has etched marks to indicate volumes, a pouring lip, and often a plastic bumper to prevent breakage C. Read at the bottom of the meniscus (at eye level) D. Use the graduations to find all certain digits 52 mL.
E. Estimate the uncertain digit and take a reading – The total volume of the graduated cylinder is 52.8 mL.8 mL.
What is the volume in this 10 mL cylinder? _. _ _ mL 626
What is the volume in this 25 mL cylinder? _ _. _ mL 115
What is the volume in this 100 mL cylinder? _ _. _ mL 527
Determining Volume – 2 ways 2. Calculation Formula A: V = L W h The numbers and units multiply – Example: 5 cm x 2 cm x 4 cm = 40 cm 3 (mL)
– Note: Be sure to know the differences in your measurements
Examples: 1. A block has a volume of 25.3 mL and a mass of 21.7 g. A. Calculate the density of the block. B. Determine the identity of the block (Table) 2. Isopropyl alcohol has a density of.785 g/mL and a mass of 20.0 g. What will the final volume be if the original volume in the graduated cylinder was 35.4 mL? 3. What is the mass (in pounds) of an aluminum bar that has a volume of 233.9 mL? (Table)