Most people think that mass is the same as weight. This is wrong, since weight depends on the strength of gravity while mass is a property of matter.
You can measure the mass of an object by using a balance. However, the measurement will change if the object changes in shape or chemical composition.
Units of Mass
Mass measurements play a vital role in everyday life and are used when we buy groceries, use medication, design bridges or space shuttles, or trade grains or gemstones. They are also important in scientific contexts, where they help us understand the properties of atoms and molecules.
The base unit of mass in the International System of Units (SI) is the kilogram, or kg. It is defined as the mass of a cylinder of platinum-iridium alloy kept in France, and any object that has the same mass as the kilogram is said to have the same mass.
The 21st General Conference on Weights and Measures has recommended that laboratories continue to refine experiments to link the kilogram to fundamental constants, with a view to redefinition of the kilogram in the same way as the metre was recently redefined. This will allow mass scales to be realized over a range of more practical sizes.
Density
Density, also known as weight per volume, is a critical measurement in scientific research. It allows scientists to predict how a substance will interact under particular conditions such as whether it will float or sink. It’s also used as a key factor in differentiating substances that may appear similar to the naked eye.
Unlike mass, density is an intensive property. That means that a given sample of a material will have the same density on every surface and throughout the entire volume. Consequently, it is measured with standard units. Precision of both mass and volume measurements is crucial to ensuring accurate density calculations. Slight errors in either of these can lead to large discrepancies in calculated density. This is why instruments are calibrated on a regular basis to ensure they are functioning properly.
Temperature
Having accurate measurement tools is important for all lab sciences. Traditional instruments like rulers and tape measures are reliable for simple length measurements, while laser distance meters offer unparalleled accuracy for advanced measurements. Analytical balances and digital scales are used to measure mass in scientific laboratories, kitchens, and retail settings.
Temperature is defined as the average kinetic energy of particles in a substance minus any kinetic energy associated with macroscopic movement. For example, a hot ball has high kinetic energy because it has more particles that are bouncing around faster, but this doesn’t necessarily mean that it has higher temperature.
Errors in mass measurement can occur due to a number of factors, including balance drift, air currents, lack of thermal equilibrium, magnetic or electrostatic fields and human manipulative skills during weighing. Good laboratory techniques and standards can help eliminate or reduce these sources of error.
Pressure
Four quantities must be known in order to describe a sample of gas: temperature, volume, amount and pressure. Pressure is force per unit area. The SI unit of pressure is the pascal, while the American standard is the pound per square inch gauge (psi).
Pressure may be expressed in terms of the height of a column of a given fluid in a manometer or as the difference between atmospheric and the measured pressure. The latter is often expressed in hectopascals (hPa), although many meteorologists continue to use millibars as they have done for centuries.
Negative pressures, like vacuum, are also measured. Measurements of vacuum require special consideration because small changes in the reference pressure or even the temperature will have large effects on the vacuum readings.
Weight
Mass is the quantity of matter in a body and it determines an object’s resistance to changes in motion (inertia). It is independent of dimensions and size. Two identically sized objects can have different masses, and an object’s mass does not change even when it is in space or on Earth.
Weight is the force exerted by gravity on an object’s mass. The SI unit of weight is the Newton, which is equal to the amount of force required to accelerate a kilogram of mass at a rate of one meter per second squared.
Conventional mass is measured by a spring scale or another instrument that balances in air. Primary calibration laboratories use a variety of designs for mass standards, including the three-in-one and four-equal-weight systems.