Chemists have developed a method to use carbon nanotubes, which are 50,000 times thinner than human hair, to form pencil lead. This pencil lead is used to complete electric circuits in gas sensors printed on paper with gold electrodes. The sensors can be modified to detect specific gases, as gas molecules bind to the nanotubes, disrupting the current flow and breaking the circuit. Practical applications include detecting sulfur compounds in natural gas leaks and ethylene released by ripening fruit.

What is the thickness of the carbon nanotubes used in the pencil lead compared to human hair?

• 1,000 times thicker

• 100 times thinner

• 50,000 times thinner

• 10 times thicker

What material is used to print the paper for the electric circuits?

• Aluminum

• Gold

• Silver

• Copper

How do gas molecules affect the carbon nanotube sensors?

• They change the color of the nanotubes

• They make the nanotubes thicker

• They disrupt the current flow

• They enhance the current flow

Which gas can be detected by the sensors to indicate a natural gas leak?

• Nitrogen

• Carbon dioxide

• Sulfur compounds

• Oxygen

What is one application of the sensors related to fruit?

• Detecting fruit color

• Measuring fruit weight

• Detecting ethylene released by ripening fruit

• Calculating fruit sugar content