Question

You are told that an unknown liquid has a density of \(0.79 \mathrm{~g} / \mathrm{cm}^{3}\) and will not mix evenly with water. Predict what will happen if you pour some of this liquid into a glass of water, stir, and wait five minutes.

Short answer

The unknown liquid will float on top of the water.

Step-by-step solution

Understand Density

Density is the mass per unit volume of a substance. It is an important property that determines how substances interact, especially when mixed with liquids like water.

Compare Densities

The density of the unknown liquid is given as \(0.79 \text{ g/cm}^3\), which is less than the density of water (\(1.00 \text{ g/cm}^3\)). This means the unknown liquid is less dense than water.

Predict the Interaction

Since the unknown liquid is less dense than water and they do not mix evenly, the liquid will float on top of the water instead of mixing with it.

Stirring Effect Analysis

When stirred, the two liquids may form temporary suspensions. However, due to the fact that they do not mix evenly, the lighter liquid will eventually rise back to the top after stirring stops.

Wait and Observe

After waiting five minutes, the separation of the liquids will become evident as the unknown liquid floats on the top surface of the water due to the density difference.

Key concepts

Liquid Density

Liquid density is a measure of how much mass is contained within a certain volume of a liquid. This concept is crucial as it influences how liquids behave when they are combined. The density of a substance is calculated as mass divided by volume. It is commonly expressed in units of grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).

In any liquid mixture, density determines whether the components will mix evenly or separate. For example, a liquid with a higher density than another will usually sink beneath it if the two are combined. Conversely, a liquid with a lower density will float on top of a denser liquid. Understanding liquid density helps predict how substances will arrange themselves when poured together.

Density Comparison

Density comparison involves evaluating the densities of two or more substances to predict how they will interact if combined. In this context, knowing that water has a density of 1.00 g/cm³ is important. This value serves as a reference point.

For instance, if we have a substance with a density of 0.79 g/cm³, as is the case with the unknown liquid in the exercise, we know that it is less dense than water. This implies that the substance will not sink but instead float when put in water. Making these comparisons allows us to infer outcomes of physical interactions without physically mixing the substances ahead of time. Such foresight can be quite useful in laboratory settings or any scenario involving multiple liquids.

Buoyancy in Liquids

Buoyancy is the force that causes objects or substances to float in a fluid. In liquids, buoyancy occurs because of differences in density and the upward pressure exerted by the liquid. When a liquid is less dense than another, it experiences an upward force that keeps it at the surface.

In our scenario with the unknown liquid at 0.79 g/cm³, buoyancy ensures that it floats on the surface of water, which is denser. This behavior stems from the principles of buoyancy that Archimedes described long ago. Factors affecting buoyancy include the densities involved and gravitational forces in the environment. Stirring changes the positioning temporarily, but the less dense liquid will always return to the top due to buoyancy effects.

• Buoyancy depends on density differences.
• Less dense liquids experience greater buoyant forces.
• Once stirring stops, less dense liquids rise again due to buoyancy.

Understanding buoyancy helps explain why certain liquids never mix, no matter how much you try, creating distinct layers based on density differences.