When you try to dissolve sugar in water, it gradually takes on a new form and seems to become part of the water itself. Does this make the act of sugar dissolving in water a chemical or a physical change?
It is essential to first understand what to expect from both these changes so that we can then determine where this particular change falls. Let’s take a look.
Physical and Chemical Changes
Changes can be physical or chemical.
Physical changes are those that involve a change in the appearance or form of a substance when it comes in contact with an external factor that can facilitate this sort of change. When there is a physical change, there is no change in the chemical structure or configuration of the substance.
Generally, this implies that it is possible to reverse the physical change and bring back the substance to its original form. For instance, carrying out evaporation in one kind of mixture that involves water can result in the substance remaining behind and getting back to its original state or phase.
On the other hand, chemical changes are those that involve the substance combining or reacting with another substance to undergo a change in the actual structure or composition as well. There might also be a change in the form of the substance due to the chemical reaction, often resulting in completely different final products.
When it comes to chemical changes, it is not as easy as a physical reversal to change the substance back to its original form unless there is another chemical reaction that takes place.
Is Sugar Dissolving in Water a Chemical or a Physical Change?
Based on the meanings of chemical and physical changes, sugar dissolving in water is a physical change. Let’s take a look at the reasoning and explanation behind this so that you can understand the process better.
No Chemical Reaction
When you dissolve sugar in water, there is no chemical reaction that takes place. Sugar and water do not react chemically with each other to form a completely new compound but continue to retain their chemical structures even after the dissolution takes place completely.
As part of this, while it might seem that the sugar has changed its chemical composition, it has only actually undergone a change in its appearance and form. The sugar crystals simply separate into smaller particles and keep themselves steady in the water.
If it were a chemical reaction, the water and sugar would have formed a new substance entirely. It may have even led to a visible change or alteration in the appearance of the mixture.
Considering that sugar dissolving in water is a physical change, it also undergoes a change in its form to become and remain suspended in the water. Here, the water does not go through too much of a change.
Instead, the sugar cubes end up breaking apart and separating into smaller particles that then spread throughout the container holding the water instead of resting at the bottom. Chemically, the sugar remains the same.
This can slightly change the color of the water as well. Thus, the main change that occurs here is in the form or appearance of the sugar, making this a physical change instead of a chemical one.
Despite going through a change in the form, you should note that the sugar is still sugar in the water (and the water is still water). If it were a chemical change, the two would have ended up reacting, combining and forming an entirely new compound and result from the reaction.
Since this is unlikely to take place, sugar dissolving in water remains a physical change through and through. This is quite similar to mixing salt in water since the mixture will only alter the form and taste, but not the actual chemical structure of each substance.
How exactly can you tell whether or not the identity of a substance mixed with another remains the same? Is it common to all kinds of physical changes? While there is no foolproof way of figuring out that a physical change has taken place, it is certainly possible to bring the substance back to its original form to figure it out.
A reversible process is one in which you can reverse or bring back the changes that took place in the mixture. For instance, by applying an external condition or factor to the mixture, you can force the mixture to once again undergo a physical change, but this time by acting on the second substance.
For instance, if you evaporate all the water from the sugar and water mixture, the water will now change its form to vapor, leaving the sugar crystals behind. You can then condense and crystallize the sugars to get them back to their original form.
The very fact that the sugar crystals remain behind instead of evaporating with the water itself can imply that this change was physical in nature. While this method might not work for reversing every kind of physical change, it can certainly be a good way to figure it out for this particular mixture.
No New Bonds
There are no new bonds formed between sugar and water as part of the physical change that takes place between them. The atoms of each substance remain intact and do not typically form bonds with the other atoms present around them. This signals a physical change instead of a chemical one.
It is clear that for a substance to undergo a physical change, it generally needs to change its physical form without changing its internal or chemical structure.
This is the case for sugar dissolving in water as well since while the sugar might break down and take on a new form, it still remains sugar and can also be re-obtained through a simple reversal.
Without any bonds forming between the two substances and new compounds forming between them, this process is certainly a physical change.