In Investigation One, you explored how matter can be characterized by two distinct types of properties, qualitative and quantitative, and that both properties are necessary when identifying matter. Investigation Two provided you with an opportunity to explore the quantitative property of mass and its measurement. You discovered that knowing the mass of two substances or objects allows for a more accurate comparison of their amounts of matter than simply knowing the quantity or shape of each.

In addition, you found that mass is more accurate for comparing the amount of matter between two substances than the qualitative property of shape. In Investigation One you compared the metal cube with the woodblock with both the pan balance and the triple beam balance and found that although the woodblock was larger than the metal cube, the metal cube had greater mass. Had you actually measured the size of the woodblock and the metal cube, however, you would have discovered that the woodblock had a volume nearly six times that of the metal cube.

Volume

Like mass, volume is an extensive property of matter and thus dependent on sample size. Mass, however, is a function of the chemical composition of a substance and is not dependent upon the form or shape that matter takes. For example, 10 grams of liquid water in a closed 100 ml flask would only occupy 10 ml of space in that flask, but the gaseous form may occupy the full 100 ml, as gas always expands to fill a space under conditions of normal pressure and temperature.

When comparing two samples of different compositions that are in the same state of matter, volume plays a significant role. A classic example would be the traditional comparison of a kilogram of lead (chemical symbol Pb) with a kilogram of feathers. The masses are equal and both are solids; however, a kilogram of feathers takes up considerably more space (has a much greater volume) than a kilogram of lead. The relationship between mass and volume is something called density. You will learn much more about the property of density later, in a CELL called Density, that is devoted to it. For now, let’s focus on volume, as it is an important quantitative property and the accurate measurement of volume is necessary when quantifying matter used in chemical reactions.

Volume of Liquids

Volume is especially important when measuring liquids. Scientists frequently rely on volume when mixing chemicals for use in the laboratory, and understanding how to accurately measure volume is an essential step in understanding how substances interact.

Solids, liquids, and gases all have the capacity to interact with one another. Solids can combine with other solids, or with liquids, or gases. Liquids interact with solids and gases as well as other liquids when combined. When substances interact, they may remain separate from one another, as when two tables are placed end to end. The tables are interacting because they are touching, but they are not mixed.

When two substances mingle as they interact, they form a mixture. Italian seasoning is a mixture. The particles of the different herbs disperse between each other, but the oregano, thyme, and basil particles remain visible in the mixture. Scientists refer to this type of mixture as a heterogeneous mixture. However, if two substances interact and form a mixture that is uniform throughout, the mixture is homogeneous. One type of very important homogeneous mixture is a solution.

The components of a solution are called either solutes or solvents, depending upon how they behave in the solution. When two substances in the same form are combined, such as water and vinegar, then the solute is the one present in the smaller amount and the solvent is the liquid present in the larger amount. In a solution formed from 20 ml of vinegar and 80 ml of water, for example, vinegar is the solute because it is present in a smaller amount. Water, then, is the solvent.

Combining substances of different forms changes the definitions of solute and solvent. The solute is the component that changes phase, while the solvent is the component that retains its original form. In a solution of salt and water, salt goes from being solid to being liquid and therefore is the solute. Water starts and ends as a liquid, and therefore is termed the solvent. This ability of a solute to change phase is referred to as its solubility. Substances that change phase in solution are said to dissolve. When a solute dissolves, its particles (molecules) separate and disperse evenly throughout the particles (molecules) of the solvent. When salt dissolves in water, the salt separates into its component parts, sodium (Na) and chloride (Cl). The chemical composition of the salt does not change, however; if the water is evaporated away the salt will return to its solid form. Gas also dissolves into liquid, an ability that allows the creation of carbonated beverages.

When liquids form solutions with other liquids, neither liquid changes phase. Instead, the particles (molecules) of each liquid spread out and disperse evenly throughout the molecules of the other. This can easily be seen when blue food coloring is added to water. The molecules of the food coloring spread evenly between the water molecules, making the water a uniform shade of blue. The ability of two liquids to form a single-phase, or layer, is called miscibility.

Liquids are said to be miscible in each other if they form a single phase without separating. In contrast to the food coloring and water, oil and water are not miscible in one another. Vigorous shaking of the two liquids together might briefly result in the appearance of a uniform solution. However, the oil and water quickly separate into two distinct layers once the shaking stops.

Solids also can form solutions if combined with one another. However, they often are melted before this happens. Examples of solid solutions would be metal alloys such as bronze, brass, and steel. The different metallic components are melted in a furnace and solidify into a single phase when cooled.

Investigation Three introduces you to the use of the graduated cylinder as an appropriate tool for the measurement of volume and provides an opportunity for you to explore how solids and liquids interact. You will create examples of mixtures and solutions, learn to identify the components of solutions, and learn how to distinguish between solubility and miscibility through observation of the results of your experiments.