In the lab, mass is usually measured using a balance scale. This is different than the spring-type scale that you might find in your home or at the doctor’s office.
Mass is often confused with weight, which is a measure of the force of gravity on an object. However, it is important to understand the difference between the two measurements.
Gravitational force
Gravity is the force that pulls all objects, including people and planets, towards each other. It is the weakest of the four fundamental forces and is responsible for everything from tides to orbits of planets, stars, galaxies and light.
The strength of gravity depends on two things – the mass of the object and the distance between the objects. This relationship is described by Newton’s universal law of gravitation: the force of attraction between two masses is proportional to their product and inversely proportional to the square of the distance between them.
Scientists can measure the strength of an object’s gravity to within a few percent using a device called a torsion balance, which is similar to a beam scale used by greengrocers. The test mass (like a sphere) is attached to one end of a thin rod and balanced by a counterweight on the other end. The rotation of the torsion balance is directly proportional to the amount of acceleration due to gravity on the test mass.
Mass
Mass is one of the seven base SI units and is measured in kilograms (kg). It describes the amount of matter an object contains. An object’s mass will stay the same regardless of its location in the universe and does not depend on gravity. Weight, on the other hand, does.
For example, a pillowcase filled with feathers has more mass than a pillowcase filled with bricks. This is because the atoms in the bricks are much denser than those in the feathers, so they have more mass.
An object’s mass shows how much it resists speeding up or slowing down when a force is applied to it. For instance, a kitten has less mass than an elephant because it takes a lot more force to push a large animal. An elephant’s mass is also greater because it has a larger number of atoms. This is why an object’s weight increases when it approaches the speed of light, as described in Einstein’s theory of special relativity.
Weight
Although many people use the words weight and mass interchangeably, they are not the same things. Mass is the amount of matter in an object, while weight is the force exerted by gravity on that matter. This force varies by location, so an object can weigh differently on different planets.
Scientists use various tools to measure the mass of objects, including balances and scales. These tools compare the object under consideration with another known mass, such as a standard kilogram. The most accurate tool for determining an object’s mass is an analytical balance, which uses electric current to apply a force that is proportional to the mass of the test substance.
A kilogram is the most common SI base unit for measuring mass, but other units are used for very small and large objects. For example, astronomers measure the mass of stars and galaxies using a balance that can be calibrated with a set of certified standard masses.
Measurement
In chemistry laboratories, mass measurements are typically performed using a balance or scale. This type of instrument uses the principles of Hooke’s law and subtraction to determine mass. It is important to ensure that the instrument is clean and free of debris or chemicals before taking a measurement. Additionally, you should tare the balance before placing a sample on it. This process subtracts the weight of the container from the total mass measurement.
In cases where mass cannot be determined using a scale, such as when measuring liquid in a tank, scientists use transducers to measure the mass properties of the liquid. These devices send a signal to a processor, which makes the mass calculations and displays them on an indicator.
In theory, if repeated measurements are taken, the average measured mass should gradually get closer to the calculated exact mass. However, this is not always the case as external factors such as temperature changes and vibration may influence measurements.