in this video I'm going to talk about SI unit and si perix si unit is an international units for the quantity and it's made up based on the seven major quantity that you can see it in this table the SI unit for length is meter and the symbol for meter is lower case M the second quantity for SI unit is mass the unit for mass in SI system is kilogram and the symbol is lowercase k the third one is time and the SI unit for time is second and lower case s is the symbol for Time s i unit for temperature is Kelvin and the symbol for Kelvin is K upper case the amount of substance that is very important in chemistry has mole unit and the symbol is almost same but it doesn't have e at the end of that the last two quantity for SI is mostly belong to the physics but I'm going to explain also these two here electric current the unit is ampere and the symbol is a and luminous intensity the unit is Candela and the symbol is CD all other units in physics chemistry and other science major is built on based on these seven units for example if you want to calculate area for an S square or for a rectangle we are going to multiply X time y or x * X so we should multiply these two length here so if you want to calculate the S units for the area we should have length time length the unit for length is meter so meter * meter is equal to meter Square so the s unit for area is meter Square for volume we have length time lens time lens so the s unit for volume is M * m * m so is meter Cub so let's have more example for the other quantity like speed or velocity you know the definition for speed or velocity is distance over time the unit for distance is meter and the unit for time is second so SI unit for speed or velocity is meter per second for acceleration you know the definition of acceleration is change of speed per time we already know the unit for change of speed it should be the same with the unit of speed so it's meter per second then the unit for time again is second so this one is equals to me/ second Square from the second law of Newton we know force is equals to mass time acceleration so s unit for mass is kilogram and for acceleration is m/s square so s unit for force is equals to km/ second squ when we have a unit and denominator we can convert it to the negative power and bring it to the nominator so instead of writing km/ s² we can write it in this form also so this negative power it means this is belong to denominator just for make it easier we can write it in this form also so the unit for all other quantity can be derived from these seven major units in chemistry and also in physics sometime we have a very big or very small number and we need to convert these numbers to the scientific notation if you don't know how we can convert the numbers to the scientific notation you can watch my video about the scientific notation the link is on the description of this video so let's say we have this number after converting to the scientific notation or we have some number like this to make it easier instead of using this power of 10 we are able to use some perix in the International System or Si I'm going to list some of these perix in this table the power for Giga is positive 9 and the symbol is G another prefix is Mega the power for Mega is positive 6 and the symbol is m kilu positive3 K CTI -2 lower case C mli -3 M as you can see here for Mega and M both of them is M so it's very important to know is it upper case or lower case micro -6 and symbol for micro is a girc Le we call it mu nano9 lowercase n and Pico -2 and P so let's have some example for application of this perfix the -3 power is belong to the mlie so instead of 10 to3 I just simply put its symol so I can write 1.2 mg for next example we have 10 to9 and we can see here 10 to 9 it means Nano so I can just write 5.22 instead of 10 to 9 I'm going to put its symbol and and then the unit for this so then 5.22 nanom meter here is another example 8.9 * 10 to postive 9 Herz then 10 to postive 9 it means Giga so I can just write the symbol for Giga here here then it's going to be 8.9 gz thank you for watching this video for watching more video please subscribe our YouTube channel