Frozen water pipes often burst, will a mercury thermometer break if the temperature of the thermometer is brought
below the freezing point of mercury?

Therefore, when the temperature drops below 4°C, the volume of the water increases continuously. Therefore, frozen water pipes burst. Mercury contracts when cooled, so a mercury thermometer would not break if the temperature went below the freezing temperature of mercury

Alinear relationship would look like a straight line on the graph. it could have a positive negative or 0 slope. so it could be a line potentially going in any direction but it must be perfectly straight.