Notes A. Measurement

1. Notes A. Measurement 9.3.2014

2. DQQ 9.4.2014 • Which of the following is true regarding lab safety? • A. Eyeglasses provide as much protection as safety goggles. • B. It is okay to chew gum in the lab, but food items or drinks cannot be consumed. • C. You may not use glassware that is chipped or broken, but a small crack is fine. • D. If you have chemicals left after a lab experiment, you may not return them from their original bottle, they must be thrown away.

3. Measurement Notes • Accuracy: As close to the actual or correct number as possible. • Precision: The measurement is repeated to show the same results.

4. Measurement Notes • Length/Width: • Use a ruler or meter stick • Measure in centimeters (cm) or meters (m) • Circumference: • Distance around an object • Use a string and ruler • Units are in cm • Diameter • Distance across an object

5. Measurement Notes • Mass: • Amount of matter in an object • Use a balance or electronic scale • Measure in grams (g)

6. Measurement Notes • Time: • Use a stopwatch • Measure in seconds (s) • Temperature: • Average kinetic energy of an object’s molecules • Use a thermometer • Measures in  °C,    °F, K

7. Measurement Notes • Volume: • How much space an object takes up • Measure with a graduated cylinder • Units are in L or mL for liquids • Units are in cm3 for solids

8. Measurement Notes • Volume by Displacement: • Used for objects with irregular shapes • 1.) Fill a graduated cylinder with 50mL of water • 2.) Drop object carefully into water • 3.) Record new volume in graduated cylinder • 4.) Subtract final volume from the initial volume of 50mL to get the volume of the object

9. Finding Density • 1.) Mass the item in grams • 2.) Use displacement method to determine the volume • 3.) Density= mass/volume (g/mL) • D=m/v