Understanding Significant Figures
Significant figures tell us which digits in a measurement are reliable. When you measure something, not all the digits in your result have the same level of certainty.
The rules for counting significant figures are straightforward. Non-zero numbers are always significant, and zeros between non-zero numbers count too. Placeholder zeros (those before non-zero digits) don't count, but zeros after non-zero digits are significant if there's a decimal point in the number.
Scientific notation helps express numbers clearly. For example, 1500 becomes 1.5×10³ by moving the decimal point three places left. Similarly, a very small number like 0.00231 becomes 2.31×10⁻³ by moving the decimal point three places right.
Quick Tip: When in doubt about significant figures in a number, try converting it to scientific notation. The digits you write in the coefficient (the part before the 10) are your significant figures!
Practicing sig fig identification is essential. For instance, 35g has 2 sig figs, 3.507km has 4 sig figs, and 0.0035kg has only 2 sig figs (the zeros at the beginning are just placeholders). Remember that all digits after the decimal in a number like 240.00g are significant - giving it 5 sig figs total.
