Question

1. why do you need to be careful not to let the bulb of the thermometer touch the bottom or sides of the container?

Explanation:

The container walls or bottom may have a different temperature from the substance being measured due to heat transfer with the surroundings or heating/cooling sources. If the thermometer bulb touches them, it will measure their temperature instead of the accurate temperature of the substance.

Answer:

To get an accurate temperature reading of the substance inside the container, as the container's bottom and sides may have a different temperature and affect the thermometer reading.