How does mixing affect the dissolving of ingredients

The point of this experiment, in addition to learning whether salt or sugar dissolves faster in various liquids, is to learn how molecules interact in a solution. As you saw in the preceding illustration, the water molecules take up most of the room in the container.

But there is still some available space in which the sugar or salt molecules can fit. Through your experiment, you'll learn how fast the sugar molecules fit into those spaces, as compared to the salt particles.

Knowing this will help you better understand the process that occurs as a substance dissolves. The control in your experiment will be water.

The other liquids in which you dissolve salt and sugar will be the variables. Remember when you conduct your experiment that it's very important that the liquids you use are all the same temperature. You already learned that sugar dissolves faster in a warm liquid than in a cool one, so you know it wouldn't be an accurate experiment if some of the liquids you use are warm and some are cold.

The temperature of the liquid would become a variable. Therefore, all the liquids you use? If you normally keep them in the fridge, be sure to allow them to sit out on the counter overnight until they are all the same temperature. To give you a little more flexibility when you conduct the experiment, you may choose the liquids in which you'll dissolve sugar and salt. There's no point in having to go out and buy additional liquids if you've already got what you need. Don't assume that liquids that have been sitting in different areas of your house are the same temperature.

A bottle of soda that's been sitting in the garage, for instance, may be several degrees cooler than rubbing alcohol from the bathroom closet, or apple juice from the kitchen pantry. Be sure to have all liquids in the same location in order for them to achieve the same room temperature. If you don't, the results of your experiment won't be valid. Just make sure you choose liquids that are different from each other in taste, color, odor, and purpose.

You'll also need to select those that allow you to observe the salt and sugar as it dissolves. If you use milk or orange juice, for example, you won't be able to watch the salt and sugar dissolve. Some suggestions for liquids to consider are:. All of these are commonly found around the house, perhaps saving you a trip to the store. Now that you know how solutions are formed and some of the factors that will affect the speed at which the sugar and salt you'll be using will dissolve, you should be able to make a good guess as to which one will dissolve faster.

If you haven't done this experiment before, you won't know if the liquids you use will be a factor in dissolving salt and sugar. This makes it more difficult to form a hypothesis, but don't worry. Whether your hypothesis turns out to be correct, or not, does not affect the validity or outcome of your experiment. While you won't know until after your experiment if properties of the different liquids you choose will affect the rate at which the salt and sugar dissolve, you do know that salt crystals are generally smaller than sugar crystals.

And you know that the temperature of the liquids will not be a factor in your experiment. Just try to use your past experiences, the information you've read earlier in this section, and your common sense to come up with a sound hypothesis.

Remember that your hypothesis must be stated as an objective sentence, not a question. So go ahead and -make your guess as to whether the salt or sugar will dissolve faster, and let's get started with the experiment. Some liquids suggested for use in this experiment are white vinegar, club soda, ginger ale, glass cleaner, rubbing alcohol, apple juice, lemonade, and tea. If you want to substitute another liquid for one or more of the ones suggested, that's fine.

Just be sure that all liquids are clear and at room temperature. The amounts of materials listed below are enough for you to conduct the experiment three times with each liquid. You'll need:. When you've gathered all your materials, you'll be ready to begin your experiment. Just follow these steps:. Keep a cup of plain water in sight so you can compare it to the cups containing salt and sugar.

It will be interesting to watch how the appearances of the liquids change as the salt and sugar dissolve. It's going to take a little while for the sugar and salt to dissolve. For best results, do not stir the solutions, as doing so will present an additional variable. If you must stir, then stir each solution three times, and stop. Only stir after you notice there is solute at the bottom of each of the two containers. Stirring the solutions unevenly will cause your experiment to be invalid.

On the other hand, a mixture of ethanol and water will mix in any proportions to yield a solution. In this case, both substances are capable of hydrogen bonding, and so the solvation process is sufficiently exothermic to compensate for the endothermic separations of solute and solvent molecules.

As noted at the beginning of this module, spontaneous solution formation is favored, but not guaranteed, by exothermic dissolution processes. While many soluble compounds do, indeed, dissolve with the release of heat, some dissolve endothermically. Ammonium nitrate NH 4 NO 3 is one such example and is used to make instant cold packs for treating injuries like the one pictured in Figure 5. A thin-walled plastic bag of water is sealed inside a larger bag with solid NH 4 NO 3.

When the smaller bag is broken, a solution of NH 4 NO 3 forms, absorbing heat from the surroundings the injured area to which the pack is applied and providing a cold compress that decreases swelling. Endothermic dissolutions such as this one require a greater energy input to separate the solute species than is recovered when the solutes are solvated, but they are spontaneous nonetheless due to the increase in disorder that accompanies formation of the solution.

Watch this brief video illustrating endothermic and exothermic dissolution processes. A solution forms when two or more substances combine physically to yield a mixture that is homogeneous at the molecular level. The solvent is the most concentrated component and determines the physical state of the solution. The solutes are the other components typically present at concentrations less than that of the solvent.

Solutions may form endothermically or exothermically, depending upon the relative magnitudes of solute and solvent intermolecular attractive forces. Ideal solutions form with no appreciable change in energy. A solution can vary in composition, while a compound cannot vary in composition. Solutions are homogeneous at the molecular level, while other mixtures are heterogeneous. Therefore, the dissolution process increases the energy of the molecular interactions, and it consumes the thermal energy of the solution to make up for the difference.

Heat is released when the total intermolecular forces IMFs between the solute and solvent molecules are stronger than the total IMFs in the pure solute and in the pure solvent: Breaking weaker IMFs and forming stronger IMFs releases heat. Heat is absorbed when the total IMFs in the solution are weaker than the total of those in the pure solute and in the pure solvent: Breaking stronger IMFs and forming weaker IMFs absorbs heat.

Skip to content Chapter Solutions and Colloids. Learning Objectives By the end of this section, you will be able to:. Describe the basic properties of solutions and how they form Predict whether a given mixture will yield a solution based on molecular properties of its components Explain why some solutions either produce or absorb heat when they form. Chemistry End of Chapter Exercises How do solutions differ from compounds?

From other mixtures? What happens when the salt does not dissolve anymore? Repeat these steps with both cups labeled Epsom salts. At what point does the Epsom salts solution become saturated? Repeat the steps with the baking soda. How many teaspoons of baking soda can you dissolve in the water? Repeat the steps with the sugar.

Did you add more or less sugar compared with the other compounds? Put each of the cups containing the remaining solids onto the scale and write down the mass weight of each one. How much of each substance did you use? Subtract the measured mass from your initial mass see Preparation for each compound. What does the difference in mass tell you about the solubilities of each of the compounds? Which compound is the most or least soluble in distilled water?

Extra: Does the solubility change if you use a different solvent? Repeat the test, but instead of using distilled water use rubbing alcohol, vegetable oil or nail polish remover as solvent. How does this change your results? Extra: Can you find other substances or chemicals that you can dissolve in distilled water? How do their solubilities compare with the compounds you have tested? Extra: Solubility of compounds is also highly dependent on the temperature of the solvent. Do you think you can dissolve more salt or sugar in hot or cold water?

Test it to find out! Build a Cooler. Make a Potato Shrink--with Saltwater. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Create Account See Subscription Options. Continue reading with a Scientific American subscription.