The three typical phases (or states) of matter are gases, liquids, and also solids. Gases have actually the lowest thickness of the three, are highly compressible, and fully fill any type of container in i beg your pardon they space placed. Gases act this method because their intermolecular forces are fairly weak, so their molecules space 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 strong that the molecules are essentially locked in place. Liquids are fairly dense and incompressible, favor solids, yet they flow readily to it is adapted to the shape of their containers, favor gases. Us can therefore conclude that the amount of the intermolecular forces in liquids are in between those of gases and also solids. Number 10.1 "A Diatomic problem (O" compares the three claims of matter and also illustrates the differences 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 actually a resolved volume and also shape, and also the molecules room packed strict together. (b) fluid O2 conforms come the shape of that container however has a addressed volume; it contains reasonably densely pack molecules. (c) gaseous O2 filling its container completely—regardless that the container’s size or shape—and is composed of extensively separated molecules.

The state the a given substance depends strongly on conditions. Because that example, H2O is typically found in all 3 states: heavy ice, liquid water, and water vapor (its gaseous form). Under many conditions, us encounter water together the liquid that is necessary for life; us drink it, chef with it, and also bathe in it. When the temperature is cold enough to transform the liquid to ice, we have the right to ski or ice skating on it, pack it right into a snowball or eye cone, and also even develop dwellings with it. Water vaporThe distinction between a gas and also a vapor is subtle: the ax vapor refers to the gaseous type of a substance the is a liquid or a heavy under normal problems (25°C, 1.0 atm). Nitrogen (N2) and oxygen (O2) are thus referred to as gases, however gaseous water in the atmosphere is dubbed water vapor. Is a ingredient of the air us breathe, and it is produced whenever we warm water for food preparation food or do coffee or tea. Water vapor in ~ temperatures greater than 100°C is referred to as steam. Steam is supplied to drive big machinery, including turbines that generate electricity. The nature of the three says of water space summarized in Table 10.1 "Properties the Water at 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 also the physical and also chemical properties of atoms, ions, and molecules usually do not depend on your physical state; the individual water molecule in ice, liquid water, and also steam, for example, space all identical. In contrast, the macroscopic nature of a substance rely strongly top top its physics state, i beg your pardon is determined by intermolecular forces and conditions such as temperature and pressure.

Figure 10.2 "Elements That occur Naturally as Gases, Liquids, and also Solids in ~ 25°C and 1 atm" reflects the locations in the routine table that those facets that are frequently found in the gaseous, liquid, and also solid states. Except for hydrogen, the facets that take place naturally together gases space on the right side the the periodic table. The these, every the noble gases (group 18) room monatomic gases, whereas the other gaseous elements are diatomic molecule (H2, N2, O2, F2, and also Cl2). Oxygen can also form a 2nd allotrope, the highly reactive triatomic molecule ozone (O3), i beg your pardon is additionally a gas. In contrast, bromine (as Br2) and also mercury (Hg) room liquids under normal problems (25°C and 1.0 atm, generally referred to as “room temperature and also pressure”). Gallium (Ga), i m sorry melts at only 29.76°C, have the right to be convert to a liquid just by hold a container of it in your hand or keeping it in a non-air-conditioned room ~ above a warm summer day. The rest of the elements are all solids under common conditions.

Figure 10.2 aspects That take place Naturally as Gases, Liquids, and Solids at 25°C and also 1 atm


The noble gases and mercury occur as monatomic species, conversely, all various other gases and bromine space diatomic molecules.

Many the the elements and also compounds we have actually encountered so far are typically found together gases; some of the much more common ones are provided in Table 10.2 "Some typical Substances That room Gases in ~ 25°C and also 1.0 atm". Gas substances include numerous binary hydrides, such together the hydrogen halides (HX); hydrides the the chalcogens; hydrides the the team 15 aspects N, P, and also As; hydrides of the team 14 elements C, Si, and also Ge; and also diborane (B2H6). In addition, plenty of of the straightforward covalent oxides that the nonmetals space gases, such as CO, CO2, NO, NO2, SO2, SO3, and ClO2. Many low-molecular-mass necessary compounds are gases as well, including all the hydrocarbons with four or fewer carbon atoms and straightforward molecules such as dimethyl ether <(CH3)2O>, methyl chloride (CH3Cl), formaldehyde (CH2O), and also acetaldehyde (CH3CHO). Finally, most of the typically used refrigerants, such as the chlorofluorocarbons (CFCs) and the hydrochlorofluorocarbons (HCFCs), i beg your pardon were questioned in thing 3 "Chemical Reactions", are gases.

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

elements Compounds *HCN boils in ~ 26°C in ~ 1 atm, so it is consisted of 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 the the gas substances discussed previously (other 보다 the monatomic noble gases) contain covalent or polar covalent bonds and are nonpolar or polar molecules. In contrast, the strong electrostatic attractions in ionic compounds, such together NaBr (boiling point = 1390°C) or LiF (boiling point = 1673°C), protect against them from existing as gases at room temperature and also pressure. In addition, the lightest members of any given family of compounds room most most likely gases, and the boiling point out of polar compound are normally greater than those of nonpolar compounds of comparable molecular mass. Therefore, in a given collection of compounds, the lightest and least polar members space the persons most likely to it is in gases. Through relatively couple of exceptions, however, compounds with much more than about five atoms from period 2 or below are too hefty to exist as gases under common conditions.


Note the Pattern

Gaseous substances frequently contain covalent or polar covalent bonds, exist as nonpolar or slightly polar molecules, have relatively low molecular masses, and contain five or under atoms from periods 1 or 2.

While gases have a vast array that uses, a specifically grim usage of a gaseous substance is thought to have actually been work by the Persians ~ above the roman inn city the Dura in eastern Syria in the 3rd century AD. The Persians dug a tunnel underneath the city wall surface to enter and also conquer the city. Archeological evidence says that as soon as the Romans responded with counter-tunnels to prevent the siege, the Persians ignited bitumen and also sulfur crystals to create a dense, poisonous gas. It is likely that bellows or chimneys distributed the toxicity fumes. The continues to be of about 20 roman soldiers were found at the base of the city wall at the enntrance gate to a tunnel the was much less than 2 m high and 11 m long. Due to the fact that it is highly unlikely the the Persians can have slaughtered so many Romans at the entrance to together a border space, archeologists speculate that the ancient Persians supplied chemical warfare to successfully overcome the city.

Example 1

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

cyclohexene lithium lead carbonate cyclobutane vanadium(III) oxide benzoic mountain (C6H5CO2H)

Given: compounds

Asked for: physical state


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

B among the covalent compounds, those the are relatively nonpolar and also have short molecular masses room most most likely gases in ~ room temperature and also pressure.


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

B Benzoic acid has an ext than 4 carbon atoms and also is polar, so it is not most likely to be a gas. Both cyclohexene and also cyclobutane are basically nonpolar molecules, however cyclobutane (C4H8) has actually a considerably lower molecular mass than cyclohexene (C6H10), i m sorry again has an ext than four carbon atoms. We as such predict the cyclobutane is most most likely a gas at room temperature and also pressure, while cyclohexene is a liquid. In fact, with a boiling allude of just 12°C, compared to 83°C for cyclohexene, cyclobutane is undoubtedly a gas at room temperature and pressure.


Which compounds would certainly you suspect to be gases at room temperature and also 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 thickness of the three, are extremely compressible, and also fill your containers completely. Aspects that exist together gases at room temperature and also pressure are clustered top top the ideal side that the regular table; they occur as one of two people monatomic gases (the noble gases) or diatomic molecules (some halogens, N2, O2). Countless inorganic and also organic compound with four or fewer nonhydrogen atoms are likewise gases at room temperature and also pressure. All gaseous substances are defined by weak interactions between the constituent molecule or atoms.

Key Takeaway

The molecule in gas substances often contain covalent or polar covalent bonds, space nonpolar or contempt polar molecules, and have reasonably low molecular masses.

Conceptual Problems

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

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

How perform the microscopic properties of matter influence the macroscopic properties? deserve to you relate molecular mass come boiling point? Why or why not? have the right to polarity be related to boiling point?

For a problem that has gas, liquid, and solid phases, arrange these phases in order of increasing

density. Toughness of intermolecular interactions. Compressibility. Molecular motion. Bespeak in the plan of the molecule or atoms.

Explain what is wrong with this statement: “The state of matter largely determines the molecule properties that a substance.”

Describe the many important factors that identify the state that a given compound. What external problems influence whether a substance exist in any kind of one of the three states of matter?

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

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

Is the complying with observation correct? “All the hydrides that the chalcogens are gases in ~ room temperature and also pressure other than the binary hydride that oxygen, i m sorry is a liquid.” describe your reasoning. Would certainly you intend 1-chloropropane to it is in a gas? iodopropane? Why?

Explain why ionic compounds space not gases under normal conditions.

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Elements that exist as gases room mainly discovered in the upper best corner and also on the best side that the periodic table. The following elements exist together 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 together diatomic molecules. Just two elements exist together liquids in ~ a normal room temperature that 20°C–25°C: mercury and also bromine. The upper right portion of the regular table likewise includes many of the facets whose binary hydrides are gases. In addition, the binary hydrides of the facets of teams 14–16 space gases.