1. Density and Percent Error You’ll love it!

2. What is this Density Business? Density – a ratio of mass per volume. It is how we measure how compact or “squished together” something is. Less density More density

3. Which is more compact? So which has a larger density?

4. Now with MATH! Density = mass ÷ volume What is the density of something with a mass of 15g and a volume of 5.2mL? mDVmDV D = 15g = 2.9 g/mL 5.2mL

5. UNITS!! I’m dividing mass (g) by volume (mL), and neither of those units cancel out!! So what do I do? KEEP THEM! The unit for density is g/mL or g/cm 3. These are the same thing…

6. You Do Two! What is the density of something with a mass of 8.3g and a volume of 21.4mL? What is the density of an object with a volume of 30mL and a mass of 60g? D = 8.3g ÷ 21.4mL = 0.39 g/mL D = 60g ÷ 30mL = 2 g/mL

7. What If I Know Density?? What is the mass of something with a volume of 25mL and a density of 2g/mL? Cover up the one you NEED on the triangle. Then solve! m = D x V = 2g x 25mL mL mDVmDV = 50g

8. You Do Two What is the volume of an object with a density of 0.8 g/mL and a mass of 12g? What is the mass of an object with a volume of 12cm 3 and a density of 1.8 g/cm 3 ? mDVmDV V = m = 12g = 15mL  20mL D 0.8 g/mL m = D x V = 1.8g x 12cm 3 = 22g cm 3

9. Percent Error Percent Error - how far off your measurement is from the true value. % error = | your result - true value | x 100 % true value Absolute value: Pretend it’s positive even if it’s not x 100% x 100 in your calculator and write a % at the end of your answer.

10. See it in Action! You get a mass of 13.5g in lab. The true value is 15.2g. What is the percent error? % error = | your result - true value | x 100 % true value = |13.5 – 15.2| x 100% 15.2 = 11.18% = 1.7 x 100% 15.2

11. You Do Two You get 14.8mL, but the true value is 10.4mL. What is the % error? You get 58cm 3, but the true value is 65cm 3. What is the % error? |14.8-10.4| x100% = 4.4 x100% = 42.31% 10.4 10.4 |58 - 65| x100% = 7 x100% = 10.77% 65 65

12. Now for Lab! You need: –Goggles (cabinet in the back) –Apron (bottom drawers) –Pencil –Calculator