1. DOR: Conversions II 1) 100 FT/SEC TO CM/HOUR 2) 6000 L/MIN TO GALLONS/HOUR

2. Accuracy and Precision  How do you define these terms?

3. Accuracy  How close measurements are to the true/accepted value.

4. Precision  How close measurements are to each other.  These measurements are not necessarily accurate.

5. Percent Error  How much error you have in your lab measurements.  Comparison between your experimental value/measurement to the true/accepted value. % Error =(True – Experimental/True)x 100

6. Density and SI Units

7. Scientific Measurements  SI Units  Significant Figures

8. SI Units  Measurement system universal to scientists.  Measurement standards (base and derived)  Base unit—  Quantity we can MEASURE  Derived unit--  Quantity provided by CALCULATION

9. SI Units (cont.) Base  Mass = kilogram (kg)  Length = Meter (m)  Time = Second (s)  Temperature = Kelvin (°K) Derived  Volume = m 3, we will use cm 3 /ml  ml is NOT an SI unit  Density = kg/m 3, we will use g/cm 3 or g/ml

10. Mass vs. Weight  What is the difference?  How do we measure mass?

11. Density  Physical property of matter/substances  Used for substance identification  Provides information on how solids/liquids interact  Ratio of a substance’s mass and volume  Density = Mass/Volume  Units = SI Unit (kg/m 3 ), we will use g/cm 3 or g/ml

12. Example 1 : A student obtains a mass of 5.03 g for a metal and a volume of 3.24 ml?

13. Example 2: What is the volume of a substance with a density of 0.824 g/ml and a mass of 0.451g?

14. Example 3: A student records V1= 2.7ml and V2= 3.4 ml after placing an object in a graduated cylinder. The mass of an empty beaker is 1.13g and the mass of both the beaker and substance is 4.13g. What is the object’s density?

15. Percent Error/Density Problems 1) True value = 21.2g, Measured value = 17.7g 2) True value = 4.15ml, Measured value = 4.26 ml. 3) An object has a mass of 4 grams and a volume of 1.7 cm 3. What is it’s density? 4) What is an object’s mass if it’s density is 8.3 g/cm 3 and the volume is 4 cm 3 ? 5) What is the volume of an object with a mass of 11 grams and a density of 4.2 g/cm 3 ? 6) An object’s mass is found to be 40 grams. When this object is placed in a graduated cylinder with a V1 of 17ml, the V2 becomes 20 ml. What is the object’s density?