Final answer:
Scalar quantities are those with magnitude but no direction, including 5 m, 23 seconds, and -5°C temperature. Vectors have both magnitude and direction, such as 55 mph northwest and 5 steps east. A stopwatch is a device that measures time and shows change with its numerical display.
Step-by-step explanation:
In physics, quantities are categorized as either scalars or vectors based on whether or not they have direction. Scalars are quantities that are fully described by a magnitude (or numerical value) alone and do not include direction. Examples of scalar quantities include temperature, time, speed, energy, and mass. On the other hand, vectors are quantities that have both a magnitude and a direction. Common examples of vector quantities are velocity, displacement, force, and acceleration.
Addressing the student's question: the quantities that are scalar are: (a) 5 m, as it is a magnitude of distance without direction; (c) 23 seconds, which is a measure of time; and (d) the temperature prediction of -5°C, since temperature is a scalar quantity as it has no direction, even though it can have a negative value. The quantities that are vectors include: (b) 55 mph northwest, since it is a velocity with both magnitude and direction; and (d) 5 steps east, which is a displacement vector since it specifies a direction.
An example of a device used to measure time is a stopwatch, which indicates a change in time with the increasing numerical display as seconds, minutes, and hours elapse.