Question

how do i calculate percent change

Data: Potato Disks BEFORE Soaking (1 point for each blank) Mass Diameter Height Potato Disk "A" 20 % w/v NaCl 2.6689 2.50cm 0.40cm Potato Disk "B" 0.9 % w/v NaCl 2.6829 2.30cm 0.50cm Potato Disk "C" Distilled Water 2.8749 2.50cm - 0.50cm Data: Potato Disks AFTER Soaking (1 point for each blank) Mass Diameter Height Potato Disk "A" 20 % w/ NaCl 2.190a 2.50 cm 0.40 cm Potato Disk "B" 0.9 % w/v Naci 2.610a Potato Disk "C" Distilled Water 3.00lea 2.50cm 0.50cm Mass Calculation (1 point for each blank except 2 points for % change) BEFORE Soaking AFTER Soaking Percent Change Disk A Disk B 2.6689 2.190g 2.6828 2.610g 2.8749 3.0069 Disk C

Answer 1

The percent change is given by:

$change=100\cdot \left |\frac{m_{after}-m_{before}}{m_{before}} \right |$

Where the straight lines mean absolute value. That is, if the result of what is inside of them is positive, it remains as it is, and if it is negative, the sign is changed. (I'm sorry, but I can't use the % symbol in the equation editor, but the results are percentages!)

For Disk A:

$change=100\cdot \left |\frac{2.190g-2.668g}{2.668g} \right |=100\cdot \left | -0.179 \right |=17.9$

17.9%

For disk B:

$change=100\cdot \left |\frac{2.610g-2.682g}{2.682g} \right |=2.68$

For disk C:

$change=100\cdot \left |\frac{3.006g-2.874g}{2.874g} \right |=4.59$

4.59%