Significant figures help!!!! (1 Viewer)

[Krypton]

Hey

Just wondering....If in a question (like heat of combustion question) you get temp and mass. And the tmeperature only has two sig figs and the mass has three. Should your answer have 2 or 3 sig figs. Is temperature counted in measuring sig figs???

Thanx

 

[strawberrye]

I think there is an assumed rule in science that basically requires you to round off to the number that has the least decimal places/least accuracy in the question, so for this question, you could round it off to 2 significant figures. temperature is counted in Fahrenheit or degrees Celsius, I do not exactly get what you mean by whether it is counted in measuring sig fig, but it can be expressed to certain sig. fig. depending on the precision of the temperature measuring device-hope this helps

 

[panda15]

Yeah you round to the least accurate measurement, which in this case is 2 sig figs.

 

[Krypton]

Thankyou!!

 

[tashe]

Sorry to bring this thread back alive. However, I want to clarify just to prevent any further confusion to future readers.

1. Yes, you do round your answer off to the LEAST SIGNIFICANT FIGURE in the question. For official HSC question, the values in the question "usually" have the same significant figures.

2. WHAT IS CONSIDERED SIGNIFICANT FIGURE IN CHEMISTRY IS DIFFERENT TO WHAT IS CONSIDERED SIGNIFICANT FIGURE IN MATHEMATICS.
Example 1: 340.0 g is considered 4 significant figures in chemistry.
340 g is considered 2 significant figures in chemistry.

This is because we know that the above figure cannot be 340.1 or something, however the figure below could be. Another way to look at it, is to change it to index notation. 3.400 x10^2 is 4 significant figures.

Example 2: 0.1042 g is considered 4 significant figures.
0.0042 g is considered 2 significant figures.

This is because 0.0042 g could be changed to 4.2 x10^-3 g which is 2 significant figures.

Another example combining the two examples, are 0.020100 (the index notation is 2.0100 x10^-2). There are only 5 significant figures there. 2 0 1 0 0

That's how I looked at it in my HSC year. I do know people who say that it's the LOWEST NO. OF DECIMAL PLACES (like my chemistry head teacher). However, I believe it's the lowest significant figure. Please correct me if I'm wrong.

 

[fatassmcfat]

what 1000 considered? 1 dp or 4 dp?

Also if the question only has numbers which are like 4 or 5 dp, but i introduce a 3 dp number in calculating my answer (say, from the periodic table)- would i round up to the 3 dp? cause i used it in my calculations but it wasnt the lowest dp ASKED IN THE QUESTION, but something i put in myself. This confuses me so much and whenever i ask chem teachers they just mumble and avoid eye contact