If something is in a solid state of matter, it has a definite shape and volume. The volume of an object is the amount of space it occupies. A block of wood placed on a table retains its shape and volume, therefore, it is an example of a solid. If a liquid is poured on that same table, there are very different results. The liquid will flow out over the surface because it does not retain its shape. A liquid takes that shape of its container. If something is in a liquid state of matter, it will have a definite volume, but an indefinite shape.
Air fills a balloon. If a hole is placed in a balloon, the air will rush out. If an object is in a gaseous state of matter, it will not have a definite shape or a definite volume. Plasma has all of the properties of a gas except that it is made up of electrons instead of atoms or molecules.
Plasma exists on stars, in necular explosions, and neon signs. Water is an example of a substance that can exist in all forms of matter. Ice is solid, water is liquid, and steam is gaseous. The particles in a solid are closely packed and held in fixed positions.
This gives solids their definite shape and volume. The particles in a liquid are close together, but they are not bound to fixed positions; they can slide past and around each other. This enables liquids to take the shape of their container and to flow when they are poured.
The particles in gasses are widely separated. Their positions have no order at all and they are constantly in motion and expand to available space. Properties are characteristics that enable us to distinguish one kind of matter from another.
A physical property is observed with out changing the object in any way. The melting point or boiling points of an object are examples of physical properties. Extensive physical properties are thing like mass, length, and volume.
They depend on the amount of matter present. Intensive physical properties do not depend on the amount of matter. Examples of Intensive physical properties include melting point, boiling point, density, ductility, malleability, color, crystalline shape, and refractive index.
A physical change is a change in matter that does not result in a change in identity. Changes of state, from liquid to gas, and solid to liquid, are physical changes. At a molecular level, liquids have some properties of gases and some of solids. First, liquids share the ability to flow with gases. Both liquid and gas phases are fluid , meaning that the intermolecular forces allow the molecules to move around.
Solids are not fluid , but liquids share a different important property with them. Figure 2 shows the differences of gases, liquids, and solids at the atomic level. Most substances can move between the solid , liquid , and gas phases when the temperature is changed. These transitions occur because temperature affects the intermolecular attraction between molecules. However, the intramolecular forces that hold the H 2 0 molecule together are unchanged; H 2 0 is still H 2 0, regardless of its state of matter.
You can read more about phase transitions in the States of Matter module. First, though, we need to briefly introduce the different types of intermolecular forces that dictate how liquids, and other states of matter , behave. As we described earlier, intermolecular forces are attractive or repulsive forces between molecules , distinct from the intramolecular forces that hold molecules together. Intramolecular forces do, however, play a role in determining the types of intermolecular forces that can form.
Intermolecular forces come in a range of varieties, but the overall idea is the same for all of them: A charge within one molecule interacts with a charge in another molecule. Depending on which intramolecular forces, such as polar covalent bonds or nonpolar covalent bonds , are present, the charges can have varying permanence and strengths, allowing for different types of intermolecular forces.
So, where do these charges come from? In some cases, molecules are held together by polar covalent bonds — which means that the electrons are not evenly distributed between the bonded atoms. This type of bonding is described in more detail in the Chemical Bonding module. This uneven distribution results in a partial charge: The atom with more electron affinity, that is, the more electronegative atom, has a partial negative charge, and the atom with less electron affinity, the less electronegative atom, has a partial positive charge.
This uneven electron sharing is called a dipole. When two molecules with polar covalent bonds are near each other, they can form favorable interactions if the partial charges align appropriately, as shown in Figure 3, forming a dipole-dipole interaction. Hydrogen bonds are a particularly strong type of dipole-dipole interaction.
Hydrogen bonds occur when a hydrogen atom is covalently bonded to one of a few non-metals with high electronegativity , including oxygen, nitrogen, and fluorine, creating a strong dipole. The hydrogen bond is the interaction of the hydrogen from one of these molecules and the more electronegative atom in another molecule.
Hydrogen bonds are present, and very important, in water, and are described in more detail in our Water: Properties and Behavior module. Hydrogen bonds and dipole-dipole interactions require polar bonds, but another type of intermolecular force , called London dispersion forces , can form between any molecules , polar or not.
The basic idea is that the electrons in any molecule are constantly moving around and sometimes, just by chance, the electrons can end up distributed unequally, creating a temporary partial negative charge on the part of the molecule with more electrons. This partial negative charge is balanced by a partial positive charge of equal magnitude on the part of the molecule with fewer electrons, with the positive charge coming from the protons in the nucleus Figure 4.
These temporary partial charges in neighboring molecules can interact in much the same way that permanent dipoles interact. The overall strength of London dispersion forces depends on the size of the molecules: larger molecules can have larger temporary dipoles, leading to stronger London dispersion forces.
Now, you might ask, if molecules can develop temporary partial charges that interact with each other, these temporary charges should also be able to interact with permanent dipoles , right?
And you would be correct. These interactions are called, very creatively, dipole-induced dipole interactions. As you might have guessed, London dispersion forces and dipole-induced dipole interactions are generally weaker than dipole-dipole interactions.
These forces , as well as hydrogen bonds , are all van der Waals forces , which is a general term for attractive forces between uncharged molecules.
The primary intermolecular forces present in most oils and many other organic liquids — liquids made predominantly of carbon and hydrogen atoms , also referred to as non-polar liquids — are London dispersion forces , which for small molecules are the weakest types of intermolecular forces.
These weak forces lead to low cohesion. On the other end of the cohesion spectrum , consider a dewdrop on a leaf in the early morning Figure 6. Gases have the following characteristics:. Solids are defined by the following characteristics:.
As you can see in the video, mercury can be solidified when its temperature is brought to its freezing point. However, when returned to room temperature conditions, mercury does not exist in solid state for long, and returns back to its more common liquid form. Use the web site to answer the following questions:. Skip to main content. Matter and Change. Search for:. Explain differences among these three phases of matter. Figure 2. The properties of a substance are the properties of a huge number of particles together.
Solids, liquids and gases The three states of matter are solid, liquid and gas.
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