Salted tea

Think about magnets: unlike poles - north and south - attract , as we all know.

Salt is a crystal made up of a lattice structure formed mainly from sodium and chlorine atoms; hence, sodium chloride.

Sodium has only one valence electrons and thus readily loses its valence electron due to the relatively small nuclear charge; chlorine, on the other hand, has a greater nuclear charge, causing it to hold into its electrons more tightly. In other words, sodium is electropositive, whereas chlorine is electronegative .

In sodium chloride's ionic bond, sodium donates its lone valence electron to chlorine, which accepts the electron. This can be likened to magnets in that the sodium, now a positive ion - cation - is attracted to chloride, now a negative ion - anion .

When salt is mixed with tea, it dissolves; this is an endothermic reaction, ie it absorbs heat from its environment . This in chemistry/physics is known as enthalpy of solution: the change in thermal energy when dissolving a substance in a solvent. But why exactly is this?

That's where the magnet analogy comes in. When you pull apart two magnets, you need to do work, which adds energy to the system of magnets , specifically potential energy. In the same way, bonds in salt are being broken; this adds energy to the system - potential energy as well. Where is this energy drawn from? The small-scale vibrations of atoms: heat . If you shake two attached magnets violently enough, they too will come apart.

So putting this altogether, we now know the reason why salted tea is cooler than unsalted tea.

I must say that this is the most beautifully written wrong answer that I've seen! Latent heat of fusion is for melting, not dissolving. The thing that is involved here is standard enthalpy of solution. The SEP for NaCl is +3.88 kj/mol meaning that table salt gives off heat when it dissolves and the salted water will be hotter. There's much debate over whether dissolving is a chemical or physical change, so it's best to avoid calling it endothermic or exothermic reaction. Therefore, both the answer and the explanation are incorrect.

The heat energy of the tea is used in breaking the ionic bonds of sodium and chloride ions. Hence the overall heat energy of tea is reduced, bringing it to a lower temperature than the unsalted one.

Not to sound arrogant, but I think there's a simpler solution with the law of physics. When something is put into a hotter liquid then some heat energy will be transferred from the liquid to the object. Thus, the temperature of the tea with salt will be lower the moment the salt is added. Then, considering both cups of tea are identical, then they release the same amount of heat/second. This means that both cups' temperature decreases at the same rate. So, the salted tea will be colder.

The volume of water is reduced by the presence of salt, the lower the volume, the quicker the temperature drops.

this is because sal ansorbs heat. try it..... hold a ice cube in your hand along with some salt. after some ime it will become difficult to hold it