The three usual phases (or states) of issue are gases, liquids, and solids. Gases have actually the lowest thickness of the three, are highly compressible, and totally fill any type of container in i m sorry they space placed. Gases behave this way because their intermolecular forces are relatively weak, so your molecules are constantly moving independently of the various other molecules present. Solids, in contrast, are relatively dense, rigid, and also incompressible because their intermolecular forces are so solid that the molecule are basically locked in place. Liquids are relatively dense and incompressible, prefer solids, but they circulation readily to it is adapted to the shape of your containers, prefer gases. Us can thus conclude that the amount of the intermolecular pressures in liquids are between those the gases and solids. Number 10.1 "A Diatomic substance (O" compare the three states of matter and illustrates the distinctions at the molecular level.

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Figure 10.1 A Diatomic substance (O2) in the Solid, Liquid, and Gaseous States


(a) hard O2 has a solved volume and shape, and also the molecules space packed strict together. (b) liquid O2 conforms to the form of that is container but has a addressed volume; the contains reasonably densely packed molecules. (c) gas O2 filling its container completely—regardless the the container’s dimension or shape—and is composed of extensively separated molecules.

The state that a offered substance counts strongly on conditions. Because that example, H2O is frequently found in all 3 states: heavy ice, fluid water, and water vapor (its gaseous form). Under many conditions, we encounter water as the liquid that is vital for life; us drink it, cook with it, and bathe in it. When the temperature is cold sufficient to change the fluid to ice, we deserve to ski or ice skating on it, fill it right into a snowball or snow cone, and even build dwellings v it. Water vaporThe distinction between a gas and a vapor is subtle: the term vapor describes the gaseous form of a substance that is a fluid or a hard under normal problems (25°C, 1.0 atm). Nitrogen (N2) and oxygen (O2) are therefore referred to together gases, but gaseous water in the setting is referred to as water vapor. Is a ingredient of the air us breathe, and also it is created whenever we warm water for cooking food or do coffee or tea. Water vapor in ~ temperatures greater than 100°C is referred to as steam. Heavy steam is offered to drive big machinery, including turbines that create electricity. The nature of the three claims of water space summarized in Table 10.1 "Properties the Water in ~ 1.0 atm".

Table 10.1 properties of Water in ~ 1.0 atm

Temperature State thickness (g/cm3)
≤0°C solid (ice) 0.9167 (at 0.0°C)
0°C–100°C liquid (water) 0.9997 (at 4.0°C)
≥100°C vapor (steam) 0.005476 (at 127°C)

The geometric structure and the physical and chemical properties of atoms, ions, and also molecules usually perform not depend on their physical state; the individual water molecule in ice, liquid water, and also steam, because that example, are all identical. In contrast, the macroscopic nature of a substance depend strongly top top its physics state, i m sorry is identified by intermolecular forces and conditions such together temperature and pressure.

Figure 10.2 "Elements That happen Naturally as Gases, Liquids, and also Solids in ~ 25°C and 1 atm" reflects the areas in the periodic table that those aspects that are typically found in the gaseous, liquid, and also solid states. Other than for hydrogen, the aspects that occur naturally together gases space on the ideal side the the periodic table. The these, every the noble gases (group 18) are monatomic gases, conversely, the other gaseous facets are diatomic molecules (H2, N2, O2, F2, and also Cl2). Oxygen deserve to also type a 2nd allotrope, the highly reactive triatomic molecule ozone (O3), i m sorry is likewise a gas. In contrast, bromine (as Br2) and also mercury (Hg) room liquids under normal conditions (25°C and also 1.0 atm, frequently referred to as “room temperature and pressure”). Gallium (Ga), which melts at only 29.76°C, have the right to be converted to a liquid merely by hold a container of the in your hand or maintaining it in a non-air-conditioned room on a hot summer day. The remainder of the facets are all solids under common conditions.

Figure 10.2 elements That occur Naturally together Gases, Liquids, and Solids at 25°C and 1 atm


The noble gases and also mercury happen as monatomic species, conversely, all other gases and also bromine room diatomic molecules.

Many the the elements and also compounds we have actually encountered so far are commonly found together gases; few of the an ext common people are listed in Table 10.2 "Some typical Substances That room Gases in ~ 25°C and 1.0 atm". Gas substances include numerous binary hydrides, such together the hydrogen halides (HX); hydrides the the chalcogens; hydrides of the team 15 facets N, P, and As; hydrides the the group 14 elements C, Si, and Ge; and also diborane (B2H6). In addition, plenty of of the simple covalent oxides that the nonmetals are gases, such together CO, CO2, NO, NO2, SO2, SO3, and ClO2. Countless low-molecular-mass essential compounds room gases together well, consisting of all the hydrocarbons with 4 or fewer carbon atoms and straightforward molecules such together dimethyl ether <(CH3)2O>, methyl chloride (CH3Cl), formaldehyde (CH2O), and also acetaldehyde (CH3CHO). Finally, many of the frequently used refrigerants, such together the chlorofluorocarbons (CFCs) and also the hydrochlorofluorocarbons (HCFCs), which were debated in thing 3 "Chemical Reactions", are gases.

Table 10.2 Some typical Substances That are Gases in ~ 25°C and also 1.0 atm

elements Compounds *HCN boils at 26°C at 1 atm, so the is had in this table.
He (helium) HF (hydrogen fluoride) C2H4 (ethylene)
Ne (neon) HCl (hydrogen chloride) C2H2 (acetylene)
Ar (argon) HBr (hydrogen bromide) C3H8 (propane)
Kr (krypton) HI (hydrogen iodide) C4H10 (butane)
Xe (xenon) HCN (hydrogen cyanide)* CO (carbon monoxide)
Rn (radon) H2S (hydrogen sulfide) CO2 (carbon dioxide)
H2 (hydrogen) NH3 (ammonia) NO (nitric oxide)
N2 (nitrogen) PH3 (phosphine) N2O (nitrous oxide)
O2 (oxygen) CH4 (methane) NO2 (nitrogen dioxide)
O3 (ozone) C2H6 (ethane) SO2 (sulfur dioxide)
F2 (fluorine)
Cl2 (chlorine)

All of the gaseous substances pointed out previously (other than the monatomic noble gases) save covalent or polar covalent bonds and also are nonpolar or polar molecules. In contrast, the strong electrostatic attractions in ionic compounds, such as NaBr (boiling point = 1390°C) or LiF (boiling point = 1673°C), prevent them indigenous existing together gases in ~ room temperature and also pressure. In addition, the lightest members of any type of given household of compounds space most most likely gases, and also the boiling clues of polar link are generally greater 보다 those that nonpolar link of comparable molecular mass. Therefore, in a given collection of compounds, the lightest and also least polar members are the people most likely to be gases. Through relatively few exceptions, however, link with much more than about five atom from duration 2 or below are too hefty to exist together gases under regular conditions.


Note the Pattern

Gaseous substances often contain covalent or polar covalent bonds, exist as nonpolar or slightly polar molecules, have relatively low molecular masses, and also contain 5 or under atoms from durations 1 or 2.

While gases have a wide array the uses, a an especially grim use of a gas substance is believed to have been employed by the Persians top top the roman city of Dura in eastern Syria in the 3rd century AD. The Persians dug a tunnel underneath the city wall surface to enter and conquer the city. Archeological evidence argues that as soon as the Romans responded with counter-tunnels to avoid the siege, the Persians ignited bitumen and also sulfur crystals to develop a dense, gift gas. It is likely that bellows or chimneys dispersed the toxic fumes. The continues to be of around 20 roman soldiers were discovered at the basic of the city wall at the entrance to a tunnel the was less than 2 m high and also 11 m long. Since it is very unlikely the the Persians can have slaughtered so plenty of Romans at the enntrance gate to together a border space, archeologists speculate that the old Persians supplied chemical war to successfully overcome the city.

Example 1

Which compounds would certainly you suspect to be gases at room temperature and also pressure?

cyclohexene lithium carbonate cyclobutane vanadium(III) oxide benzoic acid (C6H5CO2H)

Given: compounds

Asked for: physical state


A decision whether each link is ionic or covalent. An ionic link is most most likely a solid at room temperature and pressure, conversely, a covalent compound may be a solid, a liquid, or a gas.

B among the covalent compounds, those the are fairly nonpolar and have short molecular masses space most likely gases at room temperature and also pressure.


A Lithium carbonate is Li2CO3, containing Li+ and also CO32− ions, and also vanadium(III) oxide is V2O3, comprise V3+ and also O2− ions. Both are mostly ionic compounds that room expected to be solids. The remaining three compounds space all covalent.

B Benzoic mountain has much more than 4 carbon atoms and is polar, so the is not likely to be a gas. Both cyclohexene and also cyclobutane are basically nonpolar molecules, however cyclobutane (C4H8) has a substantially lower molecular mass than cyclohexene (C6H10), i beg your pardon again has an ext than four carbon atoms. We thus predict that cyclobutane is most likely a gas in ~ room temperature and also pressure, if cyclohexene is a liquid. In fact, v a boiling point of just 12°C, compared to 83°C because that cyclohexene, cyclobutane is without doubt a gas at room temperature and also pressure.


Which compounds would you suspect to be gases at room temperature and pressure?

n-butanol ammonium fluoride (NH4F) ClF

ethylene oxide



Answer: c; d


Bulk matter have the right to exist in 3 states: gas, liquid, and also solid. Gases have the lowest density of the three, are extremely compressible, and also fill your containers completely. Facets that exist together gases in ~ room temperature and also pressure space clustered on the right side that the periodic table; they occur as either monatomic gases (the noble gases) or diatomic molecule (some halogens, N2, O2). Many inorganic and also organic compounds with four or under nonhydrogen atom are likewise gases in ~ room temperature and pressure. All gaseous substances are characterized by weak interactions in between the constituent molecule or atoms.

Key Takeaway

The molecules in gas substances regularly contain covalent or polar covalent bonds, are nonpolar or slightly polar molecules, and also have fairly low molecular masses.

Conceptual Problems

Explain the differences between the microscopic and also the macroscopic nature of matter. Is the boiling point of a link a microscopic or macroscopic property? molecule mass? Why?

Determine even if it is the melt point, the dipole moment, and also electrical conductivity room macroscopic or microscopic properties of matter and also explain her reasoning.

How do the microscopic nature of matter influence the macroscopic properties? deserve to you relate molecular mass to boiling point? Why or why not? can polarity be concerned boiling point?

For a substance that has actually gas, liquid, and solid phases, arrange these phases in bespeak of increasing

density. Stamin of intermolecular interactions. Compressibility. Molecular motion. Stimulate in the plan of the molecules or atoms.

Explain what is wrong v this statement: “The state of matter greatly determines the molecular properties that a substance.”

Describe the most important components that determine the state of a offered compound. What external conditions influence whether a substance exist in any type of one that the three says of matter?

Which aspects of the regular table exist together gases in ~ room temperature and pressure? the these, which are diatomic molecules and also which room monatomic? Which aspects are liquids at room temperature and pressure? Which section of the periodic table contains aspects whose binary hydrides are most likely gases at room temperature?

Is the following observation correct? “Almost every nonmetal binary hydrides space gases in ~ room temperature, yet metal hydrides space all solids.” describe your reasoning.

Is the adhering to observation correct? “All the hydrides of the chalcogens room gases in ~ room temperature and pressure other than the binary hydride that oxygen, i beg your pardon is a liquid.” explain your reasoning. Would certainly you mean 1-chloropropane to be a gas? iodopropane? Why?

Explain why ionic compounds are not gases under typical conditions.

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Elements the exist together gases space mainly uncovered in the upper right corner and on the appropriate side that the periodic table. The following aspects exist as gases: H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, and also Rn. Thus, half of the halogens, all of the noble gases, and the lightest chalcogens and also picnogens are gases. The these, all other than the noble gases exist as diatomic molecules. Just two facets exist as liquids in ~ a normal room temperature that 20°C–25°C: mercury and also bromine. The upper right portion of the routine table likewise includes many of the aspects whose binary hydrides are gases. In addition, the binary hydrides the the elements of teams 14–16 room gases.