To find the mass of 65 bacteria, you can multiply the mass of one bacterium by the number of bacteria.
Given that the mass of one bacterium is \( 1.1 \times 10^{-12} \) kilograms, the mass of 65 bacteria can be calculated as follows:
\[ \text{Mass of 65 bacteria} = 65 \times (1.1 \times 10^{-12}) \]
First, calculate \( 65 \times 1.1 \):
\[ 65 \times 1.1 = 71.5 \]
Now, we can express this in scientific notation. The number \( 71.5 \) can be expressed as \( 7.15 \times 10^{1} \).
Putting this together, we multiply:
\[ \text{Mass of 65 bacteria} = 7.15 \times 10^{1} \times 10^{-12} \]
When multiplying powers of ten, you add the exponents:
\[ 7.15 \times 10^{1 - 12} = 7.15 \times 10^{-11} \]
Therefore, the mass of 65 bacteria in scientific notation is:
\[ \boxed{7.15 \times 10^{-11}} \text{ kilograms} \]