Evaporation question

  1. It is an active process.
  2. The liquid absorbs energy from its surroundings.
  3. It only occurs at a certain temperature.
  4. The mass of the substance changes.
    Which of the following statements apply to the process of evaporation?
    A 1 and 2.
    B 2 only.
    C 2, 3 and 4.
    D 3 and 4.
    E All statements apply.

B is the correct answer but I don’t understand why statement 1 is incorrect.

It is an active process: Incorrect. Evaporation is a passive process where molecules at the surface of a liquid gain enough energy from their surroundings (due to temperature) to transition into the vapor phase.
but I don’t understand why would 4 be wrong? is it because even though the phase changes, if it’s a closed environment the amount wouldn’t change? (only phase)


Hi thanks for your reply. If evaporation is a passive process that gains energy from the surrounding environment, is condensation the opposite, an active process? Or is boiling only an active one?

To answer your question, I think it assumes the particles are in a closed system so throughout all of the physical changes the number of particles has not changed, just their spacing and arrangement.

An active process is a process which happens in the biological systems by utilizing ATP (sometimes GTP) as the energy source, as phosphore diester bonds in it are very rich in energy.

Option 4 is wrong due to the law of mass conservation. It is a physical process happening here, not a chemical one which changes the stoichiometry of the compounds. You have still the same amount/count of water molecules in the system irrespective of their physical phase or status.

Temperture is not a source of energy. Temperture is an indicator of change in thermal energy. The energy which supplies this physical change is coming from the surroundings as mentioned in the Q, more correctly from the higher energy of the surrounding molecules or better high enthalpy.


Ok so you mean active or passive process is a general term used to describe any biological process or cellular activity that requires the input of energy to perform work? Hence it has nothing to do with physical changes?

1 Like

yes you can say that. i suggest you ask chat gpt the terms of active and passive processes simply. it explains pretty well

1 Like

@Sophie Yes.
I guess, you are aware of the passive transport which does not require an energy source.

Passive transport has several types. Some happens based on concentration gradient called diffusion (e.g. K+ or Na+ channels or proton channels), some due to voltage difference (Ca2+ voltage-gated channels or Na+ voltage-dependent channels). All is called uniports too.

Active transport has also different types:

Primary active transport which uses ATP (/GTP) e.g. Na+/K+ pumps, Ca++/H+ pumps.

Secondary active transport called facilitated transport without use of ATP (/GTP) but with the help of another ions: exchanger channels also called antiports (e.g. Na+/H+ exchangers) and cotransportes also called symporters (e.g. Na+/K+/2Cl- symporters).

All examples above are examples of transport across a membrane.

Active transport happens many other places in the cell, like gliding of actin and myosin filaments of the muscles with the help of troponin which utilizes ATP. Another example is movement of dynein on actin filaments, or movement of kinesin on microtubules, all involved in intracellular transport with utilization of ATP. Phosphorylation of many precursor enzymes is another example of an active process.

I am aware, I wrote a bit above the level required for the IMAT, but good to know if questions emerge at this level. :innocent:


Wow thank you Reza. You summarized this whole concept so well! Great to review :+1:

1 Like