How can I properly use significant figures in scientific experiments?

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In summary, the conversation is about significant figures in experiments and how to properly convert a mass of 200g to MKS units. The accuracy of the 200g mass is discussed and it is advised to use the known accuracy of the balance used to weigh the mass. The conversation ends with the question of how to determine the number of significant digits if the value was not given.
  • #1
physicsbanana
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Hello,

I am having trouble with significant figuress in experiments! Thanks for any help you provide!

I have an experiment where I pick the mass, and I chose 200g. So if I want to convert this to mks units i would do the following:

200g x (1kg/1000g) = 0.2kg

Is this calculation correct/valid? Then my mass will have one sig fig because of the 200g value.

Thanks
 
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  • #2
You need start by knowing how accurate the 200g is. If it's accurate to within +/- .005g then it's 200.00g; if it's only accurate to the nearest 5g then it's 2.0 102g. Once you have that right, expressing in kg is easy.
 
  • #3
That's what i don't get...I picked a 200g mass and used it

How do I known how many significant digits if it was not a given value?

I used a 200g metal mass that was labeled "200g". Isn't this number perfect?
 
  • #4
Nothing in the macroscopic real world is exact. The set of masses should come with some statement regarding their accuracy. If not, weigh it on the most accurate balance you have and use the known accuracy of the balance.
 
  • #5
for reaching out for help with significant figures in experiments. It's important to pay attention to significant figures in scientific experiments because they help to accurately represent the precision and accuracy of our measurements.

In your example, the calculation you provided is correct and valid. When converting units, it's important to use conversion factors that have an infinite number of significant figures, such as the ratio of 1 kg to 1000 g. This ensures that the final answer has the same number of significant figures as the original value.

In this case, since the original value of 200 g has only one significant figure, the final answer of 0.2 kg should also have one significant figure. This means that the final answer should be written as 0.2 kg, not 0.200 kg or 0.20 kg.

Keep in mind that significant figures are not an indication of accuracy, but rather a representation of the precision of a measurement. It's important to use the correct number of significant figures in calculations to avoid overestimating or underestimating the precision of our results.

I hope this helps. If you have any further questions, please don't hesitate to ask. Good luck with your experiment!
 

1. What are significant figures (sig figs) and why are they important in experiments?

Significant figures, also known as significant digits, are the digits in a number that carry meaning and contribute to the precision of a measurement. They are important in experiments because they help to convey the accuracy and precision of the data collected.

2. How do I determine the number of significant figures in a measurement?

The general rule for determining the number of significant figures in a measurement is to count all non-zero digits, as well as any zeros between two non-zero digits. Trailing zeros after a decimal point are also significant. Leading zeros before a decimal point are not significant unless they are explicitly measured or indicated by a decimal point.

3. Can I round my final result to the same number of significant figures as my initial data?

No, when performing calculations with measured values, the number of significant figures in the final result should be limited to the same number as the measurement with the fewest significant figures. This ensures that the final result is not more precise than the original data.

4. Do I need to consider sig figs when using scientific notation?

Yes, significant figures still apply when using scientific notation. In scientific notation, the number before the multiplication sign represents the significant figures, while the power of 10 represents the precision of the measurement.

5. How do I handle sig figs when adding or subtracting measurements?

When adding or subtracting measurements, the final result should be rounded to the same number of decimal places as the measurement with the fewest decimal places. This is because the precision of a measurement is determined by the number of decimal places, not the number of significant figures.

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