Question

Matt, Erin, and Lauren were having a challenge to see who could dissolve a one-pound cube of sugar the quickest. Matt puts his sugar cube in a bucket of water and stirs it with a wooden spoon. Erin heats up the water before putting it into her bucket and uses a wood spoon to stir it. What must Lauren do to make her sugar cube dissolve quicker than Matt and Erin?

a. Place the sugar cube into a bucket of cold water and stir really, really fast.
b. Place the sugar cube into a bucket of hotter water and stir slower than Matt and Erin.
c. Get a smaller container with less water and put the sugar cube in it and shake it.
d. Break the sugar cube into smaller pieces, put it into hot water, and stir it.

Answer 1

Lauren should smash the sugar cube into smaller pieces, dissolve it in hot water, and stir. This increases the surface area and the hot water speeds up the dissolution process.

Step-by-step explanation:

Break the sugar cube into smaller pieces, put it into hot water, and stir it. Not only does this increase the surface area in contact with the water, but the use of hot water also increases the solubility of sugar.

Why this is the best option involves the concept of dissolution rate, which is how quickly a solute, in this case sugar, dissolves in a solvent like water. Several factors can affect this rate: the size of the sugar pieces, the temperature of the water, and the amount of agitation.

Breaking up the sugar cube increases the surface area, allowing more water to come into contact with more sugar at once. Hot water contains more energy, which helps to break bonds between sugar molecules, allowing them to disperse into the solvent more rapidly. Finally, stirring creates agitation, facilitating the movement of solvent molecules around the solute, and preventing saturation of solution right next to the solute.