Final answer:
A graduated cylinder is the best tool to measure 15.0 mL of water, ideally one that allows reading to the nearest 0.1 mL, such as a 25 mL or 50 mL cylinder. The reading should be taken at the bottom of the meniscus for accuracy.
Step-by-step explanation:
The best tool to measure exactly 15.0 mL of water for an experiment would be a graduated cylinder. When selecting a graduated cylinder, you want to choose one that offers a balance between precision and capacity. A graduated cylinder which is slightly larger than the volume you need to measure, but with clear graduations for the milliliter marks is ideal. For a 15.0 mL volume, you would likely want to use a 25 mL or 50 mL graduated cylinder that allows readings to the nearest 0.1 mL for sufficient precision without being cumbersome or overly large.
It's important to make the reading at the bottom of the meniscus, which is the curve seen at the top of the liquid level. The meniscus forms because of the surface tension between the liquid and the container. To get an accurate reading, ensure the surface of the liquid is flat (if possible) and that you are measuring at eye level to avoid parallax error.