BIOL 1406

PreLab 1.4

 

What are the SI units for measuring weight?

 

Electronic balance

 

In lab, you will measure weight using a top-loading electronic balance. These balances are expensive instruments that are easily damaged, so treat them with care. They should be kept dry and should not be jarred. Electronic balances have a digital read-out to display the weight of the object.  Your balance can measure to 2-decimal-place accuracy, meaning to the nearest 0.01 g . In order to get accurate measurements, the balance MUST be calibrated each time it is turned on. Never place the substance being weighed directly on the pan; always use a weigh boat or weigh paper. The tare button will reset the zero point after placing anything on the pan.  Accurate measurements on an electronic balance are hindered by vibrations and air currents, so make sure your balance is placed on a level and stable surface with minimum air currents in the area.

 

The basic unit of weight is the gram (g). 

 

You should be able to rapidly convert measurements between grams, milligrams, and micrograms.

 

One gram (g)   =   1,000 milligrams (mg)   =   1,000,000 micrograms (μg)
One milligram (mg)  =   1,000 micrograms (μg)  =   0.001 gram (g)

 

To convert grams to milligrams, multiply by 1,000.

3 g   x   1,000 mg/g = 3,000 mg

 

To convert milligrams to grams, divide by 1,000:

650 mg /  1,000 mg/g = 0.650 g

                                       

To convert milligrams to micrograms, multiply by 1,000.

12 mg   x   1,000 μg/mg = 12,000 μg

 

To convert micrograms to milligrams, divide by 1,000:

170 μg /  1,000 μg/mg  =  0.170 mg

 

 

Your Turn
Express the following measurements in grams:
340 mg =  Hint Check your answer.
23 mg = Hint Check your answer.
4,250 μg =   Hint Check your answer.
Express the following measurements in milligrams:
8.54 g = Hint Check your answer.
0.0006 g =  Hint Check your answer.
390 μg = Hint Check your answer.
Express the following measurements in micrograms:
0.0007 g = Hint Check your answer.
0.24 g = Hint Check your answer.
0.62 mg = Hint Check your answer.

 

 

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