366.8°F (186°C)

The sucrose in table sugar melts at 367°F / 186°C. It turns from the familiar white granulated substance to something resembling glass. (Sucrose undergoes a chemical breakdown at low temperatures; see page 221.) A properly calibrated oven won’t melt sugar when set to 350°F / 180°C but it will when set to 375°F / 190°C.

Because the process of making sugar involves heating and cooling it, sugar manufacturers have learned that the melting point of sucrose (table sugar) is 367 degrees F.

The sugar melting study showed that the reason scientists and cooks haven’t been able to isolate a definitive melting point for sugar is that sugar doesn’t melt—it decomposes. If you heat sugar quickly, using extremely high heat, it will melt at a higher temperature than it would if you heat it slowly, using low heat.

– 320° F

Can we say that the sugar melts? Give a reason. No, the sugar does not melt. The sugar particles are free, but they are mixed with the water.

In melting only one substance is involved and the liquid and solid are the same material. Heat is needed for melting to occur. Dissolving involves two materials; the resulting solution is a mixture of both. The dissolved substance is still present in the solution even though it can’t be seen.

The same amount of salt, baking soda, and sugar added into separate solutions will tend to yield the same result. Salt will always melt ice quicker than both of them. This is because in the same amount or volume, there are more molecules of salt than sugar or baking soda due to the chemical make-up.

Energy, which is the capacity to do work or produce heat, affects the rate at which a solute will dissolve. Breaking up, crushing or grinding a sugar cube before adding it to water increases the sugar’s surface area. This means the finer the sugar particles, the faster it will dissolve.

0 degrees Celsius

The rate of dissolving of a solute in a solvent is faster when the solute and solvent are stirred, the solvent is warmer, or the solute consists of smaller particles with more surface area.

Sugar dissolves faster in hot water than it does in cold water because hot water has more energy than cold water. As they move faster, they come into contact with the sugar more often, causing it to dissolve faster.

Salt dissolves better in warmer water than in colder water. This is because the water molecules are moving faster and can keep the salt ions from joining together by pulling on them.

Sugar dissolves easily in water and oil does not. Water has a low solubility when it comes to oil. Since oil is not soluble in water, it will never truly dissolve. Oil and water is a mixture, not a solution.

Factors affecting solubility

• Temperature. Basically, solubility increases with temperature.
• Polarity. In most cases solutes dissolve in solvents that have a similar polarity.
• Pressure. Solid and liquid solutes.
• Molecular size.
• Stirring increases the speed of dissolving.

The rate of dissolving depends on the surface area (solute in solid state), temperature and amount of stirring.

Solubility is Affected by pH The pH of an aqueous solution can affect the solubility of the solute. By changing the pH of the solution, you can change the charge state of the solute.

Temperature affects the solubility of both solids and gases, but pressure only affects the solubility of gases. Surface area does not affect how much of a solute will be dissolved, but it is a factor in how quickly or slowly the substance will dissolve.

For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions.

NOTE: Increasing the Temp and Decreasing the Temp are OPPOSITES. Either they have an effect on the rate or they don’t. If they have no effect at all, they would both be actions that would not increase the rate of solid dissolving in a liquid.

The Effect of Pressure on Solubility However, the solubility of gases shows significant variability based on pressure. Typically, a gas will increase in solubility with an increase in pressure. This effect can be mathematically described using an equation called Henry’s law.

In general, the solubility of a gas in a liquid is increased by the increase of pressure. As the molecules collide more with the liquid’s surface, they will be able the squeeze between the liquid molecules and thus become a part of the solution.

External pressure has very little effect on the solubility of liquids and solids. In contrast, the solubility of gases increases as the partial pressure of the gas above a solution increases.

The solubility is a measure of the concentration of the dissolved gas particles in the liquid and is a function of the gas pressure. As you increase the pressure of a gas, the collision frequency increases and thus the solubility goes up, as you decrease the pressure, the solubility goes down..

1 Solubility in Pure Water. Normally, oxygen solubility is strongly dependent on (1) the amount of dissolved electrolyte salt(s) (decreases at higher concentration of electrolyte), (2) temperature (decreases at higher temperatures), and (3) pressure (increases at higher pressure).

The solubility of a solid may increase or decrease with increasing temperature, whereas the solubility of a gas decreases with an increase in temperature and a decrease in pressure.

approximately 50 g per

As, the temperature increases, the solubility of the solute increases and vice-versa. is an ionic salt whose solubility increases as we increase the temperature. The solubility of ammonium chloride at 50°C is 50 grams.

Do I Know about Solubility Graphs?

80 g/100 g water