Mass,+Weight+and+Density

Mass, Weight & Density Mass Mass is the amount of matter present in a certain object. It does not vary from place to place. There are some misconceptions between weight and mass. Weight is actually the amount of gravitational force acting on a certain object while mass is always constant. The SI unit for mass is kg, so remember to change your answer’s unit into kilograms when answering a question about mass. I will now tell you the conversion equation for mass so that it will be easier for you to understand how to convert the mass into its SI unit. 1kg = 0.001 1kg = 1000g 1g = 0.001kg 1mg = 0.000001kg Instruments Used Since long ago, balances have been used to measure mass. They give very accurate measures and thus they have been used usually. However nowadays, the electronic balance is more popular as it is also accurate and it has a digital display for easy reading and there is an ease of handling with minimum adjustments. Below are pictures on balances and electronic balances. Weight Just like what I have stated above, weight is not similar as mass. Weight is actually the measure of gravitational force acting on an object. Thus, if an object which has a mass of 6kg on Earth, its weight will be lighter on the moon because Earth exerts a greater gravitational force on object than the moon. The SI unit for weight is N – Newton. Instruments Used Extension spring balance or a compression spring balance Below are pictures on extension spring balance and a compression spring balance. Density Density of a substance is defined as mass per unit volume. Different materials have different densities. The SI unit for density is kilogram per cubic meter (kg/m3). The equation for density is Density = Mass/Volume. Below is one way that can help you remember the equation easily. The following are to help you in changing your answers into the SI units. (M=mass D=density V=volume) 1kg/m­3 = 1/1000 g/cm3 1000kg/m3 = 1g/cm3 The object will float when its density is less than that of the fluid. The object will sink when its density is more than that of the fluid. However, when the object’s density is equal to that of the liquid, it will be freely suspended in the liquid. Substances will become less dense when heated as they expands and increases their volume.

Reflections
==== Before this lesson, I already knew that there were differences in the definition of mass and weight. However, I had a lot of difficulty trying to figure out which term meant what as I always got it mixed up together. After this lesson, I no longer jumble up the definition and know when I should use a certain term. For density, I have also used the way shown in the pictures above to easily memorise the equation to get density or other values. I noticed that it was similar to the equation for speed and as the above shown was how I learnt speed, I quickly understood the equation needed to find the density of objects. ====