Steps to follow while doing calculations in Physics and Chemistry

Posted by sreeram sudha on July 5, 2010

Sums are an important feature in the syllabus of CBSE and ICSE. By following certain steps, the working of sums in these subjects can be made easy and interesting.

Steps to follow while doing calculations in Physics and Chemistry:

1) First write the data that is given. This will enable the student to be aware of the formula, the student has to use in solving the sum.
2) Then write the formula that can be used to solve the sum.
3) It is easier to work with fraction numbers than decimals. So, convert the decimal numbers into fraction numbers, in powers of ten and after arriving at the answer, convert the fraction numbers into corresponding decimal numbers corrected up to two decimal places.
Students following the above steps while doing sums in physics and chemistry will find better comfort level.

Not only sums, but there are other interesting features in these two subjects, Physics and Chemistry.
While working with sums in Mole Concept and Stoichiometry in chemistry, the students can follow certain methods to arrive at the correct solution.
1) First write the chemical equation and balance it, by making the number of atoms of each element the same on the reactants side and the products side.
2) Always remember that One molecule of any compound weighs the sum total of atomic weights of the molecule and One mole of any gas occupies a volume of 22.4 litres or 22,400 ml or 22,400 cubic cm at standard temperature and pressure .
3) While finding the molecular formula, the student has to remember
Molecular formula = n X Empirical formula and
The value of n = Molecular weight/Empirical Formula weight.

Sometimes, the molecular weight may not be provided in the sum, instead, Vapor density would have been provided. In such cases, use the formula
Molecular Weight = 2 X Vapour density.

In Physics, while doing sums, Correct Units have to be mentioned in the final answer.
While working the sums, necessary conversions have to be made so that the Units of all the components are in the same, either in S.I or C.G.S. units.

For example, if the Distance is in Kilometers, then the unit of speed has to be in Kilometer per Hour. If the unit of speed is provided in the sum as Meters per second, then it can be converted into Kilometers per hour by multiplying with 18/5. If the distance is in meters, speed in Kilometers per hour, then the speed can be converted into meters per second by multiplying with 5/18

1) The Formula has to be written first
2) Next, the units of the individual component in the formula have to be mentioned.
3) After necessary reductions, the final unit will be available.
For example Speed = Distance in meters/time in seconds or
Distance in kilometers and time in hours, then
Speed = meters/second or Kilometers/hour
so the unit of speed is meter per second or kilometer /hour. = m/sec or km/hour

V^2 – u^2 /a = 2S (v=final velocity, u = initial velocity, a = acceleration and S = (distance) (meters per second) ^2 – (Meters per second) ^2/ Meters per second square = meters ^2 X Seconds ^2/metres per seconds ^2 = Meters which is the unit of distance.

So writing the Formula for any sum is important to make the sum interesting and easy.

In the branch of organic chemistry, to identify Alkanes, Alkenes and Alkynes,
1) First write the number of carbon atoms in the unknown Hydrocarbon and call it n
2) Then write the number of hydrogen atoms in multiples of n.
3) The general formula for Alkane is CnH2n+2; Alkene is CnH2n; Alkyne is CnH2n-2. By substituting the values of n, the student can identify the unknown Hydrocarbon.

By following a few steps in any Topic in Physics and Chemistry, the student can work comfortably and find the subjects interesting and not monotonous.