What is the difference between Chemistry and Chemical Engineering ?

Have you ever came across this question, what is the difference between Chemistry and Chemical engineering ? To put in simple words Chemistry mainly deals with the chemical aspects (like pH, electromotive force, reaction with water etc.,) of the chemicals, where as if you pick Chemical Engineering it deals mainly with physical aspects (like density, viscosity, diffusivity, boiling point etc., ). But you can find some properties commonly using in both streams.

Chemist work:

In general chemists take care of chemical reaction rates, properties of matter, research involved in the production of new chemicals. They use wide variety of equipment in laboratory to analyze the chemical behavior,composition, conductivity, pH, polarity, surface tension etc.,For example the reaction between a polar molecule and a organic compound depends on the affinity between those two chemicals. also the composition, pH of the products after the reaction will be given by the chemists.

Chemical engineer work:

Chemical engineers use the data provide by chemists to design a chemical industry. They much involve in designing the distillation columns, extractors, pressure vessels, reactors, by using the physical properties of chemicals. For example in a distillation column, temperature at the top and bottom of the column have predominant effect on the purity of chemicals.Chemical engineers used to work on simulators to solve complex problems related to process in a chemical industry.

Job profiles:

Chemists with post graduation and Ph.D have bright opportunities in the field of research. Also they can opt to work as chemists and R&D technicians with graduation.
Chemical engineers on the other hand have wide opportunities in the field of process engineering, design of chemical plants, chemical plant operation etc.,

First law of thermodynamics and sign convention of heat, work.

First law of thermodynamics

First law of thermodynamics states that

"Energy can be neither created nor destroyed but one form of energy can be converted to another form."

For example consider a ball is placed on the top of a table initially. It will have certain potential energy ( Energy possessed by virtue of its height ) as it is at a height from the ground. When it is allowed to fall from the table this potential energy will be converted into kinetic energy ( Energy possessed by virtue of its motion ). This kinetic energy will be converted to heat , sound etc., when it touches the ground.
In application of the first law to a given process, the sphere of influence of the process is divided into two parts namely system and surroundings. The region in which process occurs is the System and everything which the system interacts is the surroundings. First law of thermodynamics applies to both system and surroundings. In general,

Δ Energy of system  +  Δ Energy of surrounding  = 0

 For the above example if you consider ball as a system  initial energy is potential and final energy is kinetic,but the energy is gained by surroundings as heat and sound.

Systems are of two types.

• Open = System which exchange both mass and energy with surroundings.
• Closed = System which exchange only energy with surroundings.

For simplification here we are considering closed systems only. In general system contains some internal energy ( in the form of attractions and vibrations ) and this tend to change when the heat is added or removed, when work is done on the system or delivered by the system.For closed systems energy transfer between system and surroundings takes place in the form of work and heat. ( where as in open systems internal energy will be associated in transit also i.e., at entry and exit of the system ). For closed systems energy changes mostly occur in internal energy. So,

Δ Energy of system = Change in internal energy  = ± Q ± W 

Only change in internal energies can be found as it is hard to know the energy associated with  attractions and vibrations. Q is heat and W is work.

Sign Convention for heat and work.

Q and W always refer to system. 

• Heat given by the system, Heat produced by the system = -Q
• Heat given to the system, Heat supplied to the system = +Q

• Work done by the system, work produced by the system = -W
• Work done on the system, work given to the system = +W

Example :

Δ Internal energy  =  Q - W 

Heat is given to the system and work is done by the system.