Answer: Option (c) is the correct answer.
Explanation:
A chemical reaction is defined as the reaction where a chemical bond will break in order to form a new bond due to the formation of a new substance.
For example, 
Here, NaCl is the new substance that is formed. A chemical reaction will always bring change in chemical composition of a substance.
The production of hydrogen gas from water, the tarnishing of a copper penny, charging a cellular phone and burning a plastic water bottle are all chemical reactions.
Whereas a reaction where no change in chemical composition of a substance takes place is known as a physical reaction.
For example, chopping a log into sawdust will change the shape but it will not bring any change in chemical composition of the substance.
Thus, we can conclude that in the following list, only chopping a log into sawdust is not an example of a chemical reaction.
Answer:
3.4moles
Explanation:
Given parameters:
Number of molecules = 2.04 x 10²⁴
Unknown: Number of moles
Solution
We use the concept of mole to solve this kind of problem.
A mole is the amount of substance that contains Avogadro's number of particle i.e 6.02 x 10²³ molecules
Solving
For elementary particles:
Number of moles = 
¹ molecules
Number of moles = 
Number of moles of H₂O = 0.34 x 10¹ = 3.4moles
Answer:
None of the above
Explanation:
Work is defined as the force that moves an object through a particular distance:
Workdone = force x displacement
At constant velocity, the force on a body is zero because such a body is not accelerating.
Force is a product of mass and acceleration. Acceleration occurs only when velocity changes with time. If no change in velocity, acceleration does not occur. Therefore, no force is being applied.
From all the situations given, the condition is set at constant velocity. At constant velocity, there is no acceleration. This implies that no work is done.
