Final answer:
To label -40°C and +40°C on a number line, you mark a point at -40 for below zero and at +40 for above zero, with zero representing the freezing point of water. Zero is not the absolute lowest temperature, which is -273.15°C or 0 Kelvin.
Step-by-step explanation:
To locate and label 40°C below zero and 40°C above zero on a number line, you would place a point at -40 for 40°C below zero and another point at +40 for 40°C above zero. Zero on this scale represents the freezing point of water in the Celsius temperature scale. However, it is important to note that zero does not signify the absolute lowest temperature, which is known as absolute zero. Absolute zero is the point where all molecular motion ceases, and it is technically unattainable. Absolute zero is at -273.15°C, or 0 Kelvin (K) on the Kelvin temperature scale, where the size of the degree increment is identical to that in Celsius and there are never negative values.
In this context, -40°C and +40°C represent temperatures in the Celsius scale that are equally distant from the freezing point of water but in opposite directions. The number line would clearly show these points on either side of zero, illustrating the temperature changes relative to the freezing point.