Liquid state empty space

In the liquid state the forces of attraction among particles are great enough that disordered clustering occurs. The particles are so close together that very little of the volume occupied by a liquid is empty space. As a result, it is very hard to compress a liquid. Particles in liquids have sufficient energy of motion to overcome partially the attractive forces among them. They are able to slide past one another so that liquids assume the shapes of their containers up to the volume of the liquid. 

This chapter continues to explore states of matter by focusing on the gas state. Table 8.1 summarized the main features of gases. In the gaseous state, molecules are much farther apart than in either solid or liquids. Because of this distance molecules in the gaseous state have virtually no influence on each other. The independent nature of gas molecules means intermolecular forces in this state are minimal. A gas expands to fill the volume of its container. Most of the volume occupied by the gas consists of empty space. This characteristic allows gases to be compressible, and gases have only about 1/1,000 the density of solids and liquids. 

To understand vapor pressure, let s consider an empty jar that is partially filled with water and then covered with a lid. We will assume the space above the water in the jar contains only air when we screw on the jar s lid. After the lid is place on the jar, water molecules leave the liquid and enter the air above the liquid s surface. This process is known as vaporization. As time goes by, more water molecules fill the air space above the liquid, but at the same time, some gaseous water molecules condense back into the liquid state. Eventually, a point is reached where the amount of water vapor above the liquid remains constant. At this point, the rates of vaporization and condensation are equal, and equilibrium is reached. The partial pressure exerted by the water at this point is known as the equilibrium vapor pressure or just vapor pressure. Vapor pressure is directly related to the temperature, that is, the higher the temperature, the higher the vapor pressure. Table 9.4 gives... 

Gases are mostly empty space at normal pressures. At standard temperature and pressure (STP 1 atm pressure, temperature 273K), the same amount of matter will occupy about 1000 times more volume if it is in the gaseous state than if it is a solid or liquid. At much higher densities (for example, pressures of several hundred atmospheres at 273K) this assumption will not be valid. 

In previous courses, you learned about the properties of the different states of matter. You may recall that both solids and liquids are incompressible. That is, the particles cannot squeeze closer together, or compress. The incompressible nature of solids and liquids is not due to the fact that particles are touching. On the contrary, the particle theory states that there is empty space between all particles of matter. 

The same mole of H2O occupies only 0.0188 L in the liquid state, but after it has been evaporated into the gas state, it occupies 30.6 L. As shown by the modern technique of electron diffraction, the molecules themselves do not expand. Because they do not expand, they cannot occupy more than 0.0188 L of the 30.6 L of the gas. The volume occupied by the molecules is negligible (less than one-tenth of 1% of the total volume). Thus, most of the volume of the gas is composed of empty space ... 

Liquids and solids are quite a different story. The principal difference between the condensed states (liquids and solids) and the gaseous state is the distance between molecules. In a liquid the molecules are so close together that there is very httle empty space. Thus liquids are much more difficult to compress than gases, and they are also much denser under normal conditions. Molecules in a liquid are held together by one or more types of attractive forces, which will be discussed in the next section. A liquid also has a definite volume, since molecules in a liquid do not break away from the attractive forces. The molecules can, however, move past one another freely, and so a liquid can flow, can be poured, and assumes the shape of its container. 

Early theories of the state of the solvated electron suggested that it was located in a cavity in the liquid where it was trapped by its polarisation of the surrounding medium. In the latest theory, the electron cavity is characterised by a loosely packed first coordination layer containing an appreciable amount of empty space. The high electron mobility in an electric field cannot be reconciled with hydrodynamic motion of the whole cavity, and instead it is proposed that the loosely packed structure allows the electron to jump or leak away, by quantum-mechanical tunnelling,No numerical estimates of electron conductances have yet been made on this model. 

Volume and empty space can be covered in the context of liquid state solutes. When 50 cm of ethanol and 50 cm of water are mixed, the total volume is around 96 cm. Even though particles in the hquid state are close together, there will be pockets of space where the shapes do not fit together snugly, especially since they are moving around. The particles of another substance could go into some of this space and vice versa. Mixing pasta shells and lentils... 

The same quantify of a substance occupies a much greater volume as a gas than it does as a liquid or a solid. For example, 1 mol of water (18.02 g) has a volume of 18 mL at 4°C. This same amount of liquid water would occupy about 22,400 mL in the gaseous state—more than a 1200-fold increase in volume. We may assume from this difference in volume that (1) gas molecules are relatively far apart, (2) gases can be greatly compressed, and (3) the volume occupied by a gas is mostly empty space. 

As discussed in Section 0.1, most substances and mixtures can exist in three states solid, liquid, and gas. The physical properties of these states of matter are very different. In gases, the distances between molecules are so large compared to molecular size that the effect of molecular interaction is negligibly small at ordinary temperatures and pressures. Because there is a great deal of empty space in a gas—that is, space that is not occupied by molecules—gases can be readily compressed. The lack of strong forces between molecules also allows a gas to expand to flU the volume of its container. Furthermore, the large amount of empty space results in very low densities under normal conditions. 

Gases consist of large numbers of tiny particles that are far apart relative to their size. These particles, usually molecules or atoms, typically occupy a volume that is about 1000 times greater than the volume occupied by an equal number of particles in the liquid or solid state. Thus, molecules of gases are much farther apart than molecules of liquids or solids. Most of the volume occupied by a gas is empty space, which is the reason that gases have a lower density than liquids and solids do. This also explains the fact that gases are easily compressed. 

An example concerning the states of matter may illustrate this. The states of matter (solid, liquid, and gaseous) are differentiated by the motion of the particles which they are composed of and the distance between them. In the solid state particles have fixed places in a lattice structure. They are near to each other and move only slightly. In the liquid state particles are still near to each other, but can move freely. In the gaseous state there is free movement and a lot of empty space between the particles. 

A method is shown in Figure 13.10. The apparatus consists of a barometer into which a volatile liquid may be injected. Because mercury is more dense than other liquids, the injected volatile liquid rises to the top of the mercury column in the tube and floats on top of the mercury. The volatile liquid evaporates into the empty space above the mercury (a virtual vacuum). As the liquid is converted to the gaseous state, the level of the mercury column drops as the pressure of vapor builds up. 

---