How do I turn 128.576 joules into 2 sig figs
Here is the link. Hope it helps
https://www.chemteam.info/SigFigs/SigFigs.html
1.29E2
oops
I did 3 s.f.
To 2 it is 1.3E2.
What’s E2 mean I’m so confused
1.2E2 means 1.2 x 10^2 or in other words it is 1.2 x 100. You can round 128.576 to 128.58 (5 s.f.); 128.6(4 s.f.); 128 (3 s.f.) but we have problem if we try to do less than 3 BECAUSE if we try 2 places we write 12.0 but that has 3 s.f., or 12 but we can't put another digit there without getting 3 so we write 1.2 x 10^2. That tells us it has 2 s.f. but the decimal point is two places to the right. There is a very good discussion of s.f. by the chem team. I will post a link.
To turn 128.576 joules into 2 significant figures, you need to round the number according to the rules of significant figures.
The first step is to identify the significant digits in the number. Significant digits are all digits in a number that are not leading zeros. In this case, all digits are significant.
Next, locate the digit that will be affected by rounding. In this case, it is the digit in the third decimal place (the digit after the second decimal place), which is a 6.
Now, look at the digit immediately after the one you identified in the previous step. If it is 5 or greater, you round up. If it is less than 5, you round down.
In this case, the digit immediately after the 6 is a 5, which means we must round up. Therefore, to express 128.576 joules with 2 significant figures, the rounded value would be 130 joules.