CHEMISTRY – Hey guys, here’s a pic of some “high density” koi that I saw in Hawaii (at the Dole Pineapple Plantation, of all places!). Great review on density problems today, and more! Remember, in chemistry we use math as a tool, therefore we might work problems a little differently in chemistry than you do in your math class.
When working these problems, don’t forget to follow the problem solving steps we discussed today:
- Analyze – write down what you’re given and what you’re looking for
- Plan – write a formula where you isolate the unknown on one side by itself
- Compute – plug in your data, numbers and units; then cancel the units, and if they cancel correctly, go on to the calculator. Be sure and give your answer what the correct units.
- Evaluate – does your answer make sense, have you used the correct units, do you have the correct sig figs?
Need more practice? Help session TOMORROW morning, 7:30ish A.M.
Black Block Density:
l = 4.60 cm
w = 9.60 cm
h = 2.50 cm
V = l x w x h
V = (4.60 cm)(9.60 cm)(2.50 cm)
V = 110.4 cm^3
m = 110.415 g
D = m / V
D = 110.415 g / 110.4 cm^3
D = 1.00 g / cm^3
Black Block Density:
l=12.72 cm
w=4.19 cm
h=1.28 cm
V=l x w x h
V=(12.72 cm) (4.19 cm) (1.28 cm)
V= 68.22 cm^3
m= 65.859 g
D= m/V
D= 65.859 g / 68.22 cm^3
D=0.965 g/ cm^3
Have we decided when we are turning the lab in yet?
I don’t think we have
Paper White Block Density:
L: 8.20 cm
W: 1.30 cm
H: 8.70 cm
v= l x w x h
v= (8.20 cm)(1.30 cm)(8.70 cm)
v= 92.742 cm^3
m= 42.199 g
D= m/v
D= 42.199g/ 92.742 cm^3
D= 0.455 g/cm^3
= Alpha