Numbers in Chemistry Flashcards
What is an analog measuring device?
A device in which there is a scale that must be interpreted; it is not digital.
What is the uncertainty for an analog device?
Plus or minus one-half the smallest increment.
What is the uncertainty for a digital device?
Plus or minus the smallest decimal place.
A digital scale reads 50.67 g. What is the uncertainty? What does this mean about the measurement?
Uncertainty= plus or minus 0.01 g. This means that the actual measurement is somewhere between 50.66 g and 50.68 g.
It is important to use significant figures to…
Report measurements to reflect the accuracy of the equipment used.
Which digits are always significant?
1-9.
Zeros between significant figures are…
Significant. (Ex. 5,007 has 4 sig figs.)
When are trailing zeros in a number significant?
Trailing zeros are significant only if the number has a decimal point. Ex: 100.00 has 5 sig figs, but 100 has 1 sig fig.
Zeros in the beginning of a number whose only function is to place the decimal point are…
Not significant. Ex: 0.0025 has 2 sig figs.
Zeros following a decimal significant figure are…
Significant. Ex: 0.4700 has 4 sig figs.
How do you use sig figs when multiplying or dividing?
Round your final answer to the least number of sig figs. Ex: 1.5 x 5= 7.5, but since 5 has only 1 sig fig, we round the final answer to 8.
How do you add or subtract with sig figs?
Round your final answer to the least accurate decimal place.
What is percent error?
A way for scientistst to express how far off a laboratory value is from the commonly accepted value.
How do you calculate percent error?
Find the absolute value of this: (Accepted value-experimental value) / accepted value. Then multiply that by 100.
The Metric System is also known as…
The International System of Units or S.I.
The metric system was developed in this country:
And this year:
France, 1790
The metric system is a base___system.
Base 10 system.
Mass is measured in…
Grams. g.
Volume is measured in…
Liters. L.
