Which thing remains constant apart from its location?

Mass remains constant regardless of its location. This fundamental property of matter signifies that no matter where an object is in the universe, its mass does not change. Mass is a measure of the amount of matter in an object, and it is intrinsic to the object itself. Whether an object is on Earth, in space, or on another planet, its mass remains the same. This consistency differentiates mass from weight, which varies depending on the gravitational force acting on an object. For instance, an astronaut's weight on the Moon is significantly less than on Earth due to the Moon's weaker gravitational pull, but their mass remains unchanged.

Understanding the concept of mass is crucial in various fields of science, particularly in physics and chemistry. In physics, mass is essential for calculating force, momentum, and energy. The relationship between mass and weight is often emphasized in competitive exams, highlighting that while weight can fluctuate with changes in gravity, mass is a constant. This is important when considering scenarios such as launching objects into space or analyzing the behavior of materials under different conditions.

In contrast to mass, both velocity and density can change based on external factors. Velocity is dependent on the speed and direction of an object, which can alter due to changes in motion or forces acting upon it. Density, defined as mass per unit volume, can also vary if an object undergoes a change in temperature or pressure, causing expansion or contraction. Therefore, mass is the only property from the listed options that consistently remains constant irrespective of location, reinforcing its significance in scientific studies and practical applications.