Everything that occupies space and has some weight is called matter. There are four states of matter that are; solid, liquid, gas, and plasma. However, gases, liquids, and solids are three common states of matter.
There are several properties that distinguish these states of matter from one another. For example, gases have no definite shape or volume and are more spread out than their liquid or solid counterparts. On the other hand, liquids get the shape of a container and have fixed volume, whereas, solids have fixed shapes and volume.
The behavior of particles (molecules) depends on the state of matter. Particles of solid have an organized structure. Liquid molecules are very loosely bonded, for example, in water, molecules are clumped with each other via intermolecular forces and hydrogen bonds. The substances that exhibit a gaseous state at room temperature and pressure (RTP) have random motion. They have weak instantaneous dipole-induced dipole interactions.
Differences between solid, liquid, and gases
| Solids | Liquids | Gases |
| Particles of solids are tightly packed | Particles of liquids are loosely packed | Particles of gases are free to move |
| They have fixed shapes | Their shapes are not fixed and depend on the medium | Shapes of gases are necessarily not fixed and take the space of container |
| Solids have fixed volume | Liquids have fixed volume as well | gases do not have fixed volume |
| They are highly rigid | They are less rigid | They are not rigid at all |
| Strong forces of attraction are present between solid particles | Intermediate force of attraction are present between liquids | Comparatively very weak forces of attraction are present in gases |
| They can not flow | They can flow | They can flow |
| They are not easily compressible materials | These materials can be compressed slightly | They are the most compressible ones |
| Solids have high density | Liquids have low density | Gases have the least density |
| They do not have diffusibility | They have a slight diffusibility | Gases are highly diffusable |
| Kinetic energy of solid particles is very low for which they only vibrate | Kinetic energy of liquid particles is intermediate between gases and solids | Kinetic energy of gases is very high for which they attain a random motion |
Properties of Solids
Solid particles are highly organized and tightly packed together. They are not free to move, due to their fixed positions, and they have their characteristic shape and size. The arrangement of atoms in solids can be determined by their sizes. Different elements have different sizes of atoms and molecules. The interactions between solid particles are usually ionic bonds and metallic bonds in metals. These giant covalent lattices are solids at room temperature and the binding forces in them are usually stronger than liquid and gases.
Unique results can be obtained by packing atoms of different sizes. For example, sodium (Na+) and chloride (Cl–) have different sizes in sodium chloride (NaCl). The sodium ion is quite smaller than chloride. They are bonded in a regular arrangement of Na and Cl atoms. Each Na atom is surrounded by six Cl– ions while every Cl– ion is also surrounded by six sodium ions. It has the face-centered cubic structure of a unit cell. There is still space available between sodium and chlorine due to their different sizes.
Examples of Solids
There are hundreds of examples of solids from which few are given here:
- Glass
- Crystal
- Wood
- Metals
- Salt
- Ice
- Sugar
- Brick
- Coin
- Sand
- Steel
- Frozen carbon dioxide, etc
Types of Solids
There are two main types of solids:
- Amorphous solids
- Crystalline solids
Amorphous Solids
The atoms or ions in an amorphous solid are randomly arranged such that it has irregular lattices. They do not have definite geometric patterns and are usually polymers in which long molecular chains are bonded through weak bonds. That is the reason, that amorphous solids don’t have an organized structure.
Amorphous solids have different properties. For example, glass, rubber, and plastic are amorphous solids. Glass is hard and brittle. It is sometimes referred to as a supercooled liquid, rubbers and plastics are synthetic polymers that are soft and easy to melt. The properties of amorphous solids are different due to different types of forces which make them to be called ‘Not True Solids’.
Crystalline solids
The atoms of crystalline solids are arranged in a definite and organized pattern. Each unit pattern is called a unit cell. They are the basic building block of a solid. The arrangement of atoms in crystalline solid depends on the size and forces.
Crystalline solids are the ‘True Solids’.
Types of Solids
Based on the types of forces in crystalline and amorphous solids, they are divided into four main categories:
- Ionic solids
- Metallic solids
- Atomic solids
- Molecular solids
Properties of liquids
Atoms and molecules of the liquid are packed in a defined space in a semi-organized manner. They are able to move freely. They have weak forces of attraction as compared to solids and can easily change shape according to the shape of their container.
Liquid molecules are simple and free to move. Agitation in the liquid result in the mixing of the molecules and mixing does not destroy the molecular arrangement of the liquid. Different liquids do not allow to mix with each other because they have different intermolecular forces.
The forces between the molecules of the liquid are weaker than chemical bonds. These forces are responsible for liquid molecules to stick together. There are three types of intermolecular forces in liquids.
- Dipole-dipole interactions
It is a type of intermolecular force that occurs when the positively charged species are attracted by the negatively charged species. For example, HCl is a molecule that has dipole-dipole interactions. Hydrogen is a positively charged atom while a chlorine atom is the negatively charged one. In this case, the hydrogen atom gives its electron to make a bond with the chlorine atom.
The dipole-dipole interaction occurs when the chlorine atom of one molecule attracts the hydrogen atom of another molecule because the chlorine atom is negatively charged (high electronegativity) while the hydrogen atom is positively charged in the HCl molecule.
It is a type of intermolecular force of attraction that occurs when naked hydrogen (bonded with a strongly electronegative atom e.g. F, O, N) in one molecule is attracted by other strong electronegative atoms such as oxygen, fluorine, nitrogen, etc.
Those molecules which have dispersion forces are temporarily charged. They are very weak forces and are present in neutral molecules. The electrons, from the outermost shells, come close to each other for a short period of time. The regions where electrons reside after coming close to each other become charged. This way they have little attraction with other molecules.
Examples of Liquids
- Water
- Alcohol
- Milk
- Blood
- Urine
- Gasoline
- Mercury
- Bromine
- Honey
- Vinegar
- Drinking coffee
- Acetone, etc
Read a comparative study of the strength of the intermolecular forces here.
Properties of Gases
Particles in gases are in random motion. The random motion of gases is explained through the kinetic molecular theory of gases. The collisions between gas molecules are perfectly elastic and that is the reason gases are mostly used in molecular studies.
Gases do not have well-organized particles in a particular way. Molecules of ideal gases do not interact with each other. However, real gases have some intermolecular forces like solids and liquids.
Gases have very weak forces of attraction because atoms or molecules of gases can interact with each other for a short time. They have collisions with other molecules and with the walls of the container as well. Gases have the property to fill the space in containers which is not the case in liquids or solids.
Three main factors may affect the kinetic energy of gas molecules.
- Temperature
It is the measurement of the average kinetic energy of gas particles. Particles that have high kinetic energy move very fast as the kinetic energy is directly proportional to the absolute temperature. The higher the temperature, the greater the kinetic energy of the molecules.
- Pressure
It is the measuring scale of force exerted on the molecules of gases. It occurs when atoms of gases collide with the sides of the container. Gases move in a random direction and hit the walls of the container as well.
- Volume
Volume is defined as the amount of space occupied by any state of matter. For example, a container is filled with air. This air occupies a defined space and volume in the container.
Examples of Gases
- Air
- Carbon dioxide
- Ethane
- Helium
- Hydrogen sulfide
- Nitrogen
- Oxygen
- Freon
- Natural gas
- Hydrogen
- Ozone
- Xenon, etc
Additional topics
Key Difference(s) between Solids, liquids, and gases
Concepts Berg
What are the four main states of matter?
There are four states of matter:
- Solid
- Liquid
- Gases
- Plasma
What are examples of solid, liquid, and gas?
When we take the ice and hold it in our hands, it is in the solid state. It then starts melting and converts into the liquid state. After that, it starts to vaporize which is a gas state.
- Air, ethane, methane, and oxygen are examples of gases.
- Water, ammonia, and alcohol are examples of liquids.
- Wood, crystal, and metals are examples of solids.
What is the fluidity of a solid, liquid, and gas?
The fluidity of a solid, liquid, or gas is determined by its ability to flow. Fluidity is typically described as a material’s resistance to deformation under applied stress. Solids, liquids, and gases that flow with great ease have low levels of resistance.
What are the properties of solids, liquids, and gases?
Solids have rigid structures where particles vibrate or slide past one another with minimal kinetic energy. Liquids allow some particle motion but still maintain intermolecular bonds between them. Gases have significant kinetic energy, allowing them to flow freely into any container they occupy. The same substance can exist in all three states at different temperatures and pressures. Water is a great example. Water exists as ice at 32 degrees Fahrenheit (0 degrees Celsius), liquid water between 32 and 212 degrees Fahrenheit (0 – 100 degrees Celsius), and steam above 212 degrees Fahrenheit.
Is a shadow a solid, a liquid, or a gas?
Shadow is not a matter as matter can be anything that has mass and occupies space.
What is the nature of an atom (solid, liquid, or gas)?
Atom is the structural and functional unit of everything. It is a neutral particle. It is the basic unit of matter. All states of matter are composed of atoms. Solid have arranged and organized numbers of atoms. Liquids have atoms that are loosely attracted to each other. Gases are composed of atoms that are always in random motion.
What makes solid different from liquid and gas?
Solids are composed of atoms that are regularly arranged in molecules or compounds and only have vibrations, unlike liquids and gases. Moreover, these structures are more tightly packed as compared to liquid or gases.
Reference Books
- Gases, Liquids, and Solids: And Other States of Matter By D. Tabor (Cavendish Laboratory, University of Cambridge)
- States of matter (chemistrytalk.org)
- Gases, Liquids, Solids (chem.purdue.edu)
