States of Matter
States of Matter
Q1. What is matter?
Q2. Why is matter a solid, liquid or gas?
Q3. How is the solid state classified?
Q4. What is a crystalline solid?
Q1. What is 'Matter'? Are there different kinds of 'matter'?
A1. Matter is anything that has mass and to some extent a shape. There are three main kinds of matter often referred as three states of matter and we all come across them in our daily lives. They are:
1. Gaseous: the air we breath and, feel pleasent to have blown gently is among the examples of gaseous state. This state of matter can be distinguished by low density & viscosity, great expansion & contraction with changes in pressure and temperature, ability to diffuse readily; and the spontaneous tendency to become distributed uniformly throughout any container. The air we breathe is composed of gaseous states of many elements of which only oxygen is picked by our body.
2. Liquid: the cola, coffee, tea, bear and water are all among the examples of liquid states. This state is condensed state compared to the gaseous as the molecules/ atoms are attractred toward each-other; the forces of attraction are comparatively stronger than the ones in gaseous state. Liquids are more viscous than gases because they are thicker and more resistant to flow. Liquids occupy definite volume and are not easily compressed.
3. Solid: we all live on solid earth! In solid state of matter the molecules/ atoms/ particles are closely packed and are being held together by very strong forces. The molecules are not able to move freely however they can vibrate at their fixed positions. Thus, solids have a stable and definite shape. Based on how the atoms/ molecules are arranged in a solid the solid state can be further classified into two states:
(a) Crystalline Solid State: exhibit a fixed long range order of periodic arrangement of atoms/ molecules in all the three dimensions. Among the common examples are rock-salt, sugar, metal-keys, etc.
(b) Amorphous Solid State: exhibit no or short range order of periodic arrangement of atoms/ molecules in all the three dimesions. Common examples are window glass, cotton candy, etc.
Apart from above three states of matter there are two more Less Encounteredstates of matter, they are:
4. Plasma: The matter is composed of atoms/ molecules, under the condition of standard pressure & temperature (STP) matter has electrons that orbit the atomic nucleus. If the temperature is high enough, the electrons in the valence shell acquire enough kinetic energy to escape the atom. In this condition the electrons are no longer bound in the orbits around the nucleus. This state in which a gas become a collection of negatively charged electrons which have escaped the pull of the nucleus and ions which are positively charged because they have lost one or more electrons is known as plasma state.
5. Liquid Crytals: they are niether liquid nor solid. They flow like liquid however, have some properties similar to that of crystalline solids. An example of their application is in your flat-screen LCD TV or laptop/ computer monitor, cell-phones, watches, calculators, ATM displays, etc.
Q2. How does the matter come into solid, liquid or gaseous state?
A2. Whenever, two atoms of an element (same or different) combine, the resulting molecule has possibility to exist in either of the three states of matter under the conditions of standard pressure and temperature. The factor that controls and determines the state depends on the intermolecular forces (IMF) that hold the two atoms/ molecules together when a given molecule is present in bulk quantity. In general, and with few exceptions, the trend is that the weaker IMF will lead to the formation of gaseous state, moderately stronger IMF will produce a liquid state however, a very strong IMF will lead to solid state of matter for the resulting molecule.
Q3. How does the solid state of matter be classified according to the type of inter-molecular forces between the atoms/ molecules?
A3. Refer to the following table for classification of solid state based on the type of inter-molecular forces (IMF):
| Type | Intermolecular Forces | Properties & Examples | ||
|---|---|---|---|---|
| molecular | london dispersion dipole-diple hydrogen bond | soft, low-moderate melting point, poor thermal and electrical conduction. examples: Ar, CH4, sucrose, dry ice (CO2). | ||
| covalent | covalent bonds | very hard, high melting point, variable thermal & electrical conduction. examples: diamond, quartz | ||
| ionic | electrostatic attractions | hard & brittle, high melting point, poor thermal & electrical conduction. examples: typical salts | ||
| metallic | atoms | soft to very hard, low to very high melting point, excellent thermal and electrical conduction, malleable & ductile. examples: gold, silver, copper, etc. |
Q4. What is Crystalline Solid? How does matter crystallizes? How does a solid forms single crystal and polycrystals?
A4. A crystalline solid is any solid where in atoms, ions, or molecules are ordered in well-defined three-dimensional arrangements. The crystalline solids usually have flat, shiny surfaces, or faces, that make definite angles with one another. The orderly arrangements of atoms, ions or molecules that produce these faces also cause the solids to have highly regular shapes. Quartz and diamond are two common crystalline solids.
Any compound that solidifies as a crystalline solid occurs naturally as a polycrystalline solid and rarely as a single crystal. Atoms, ions or molecules forms the polycrystalline solid at first which, further grows to form a single crystal. In order to form the polycrystalline solid there has to be sufficient number of atoms present in close vicinity of each-other which, while solidifying, forms a conglomerate that leads to the formation of polycrystals. If for however, this solidification and conglomeration occurs in a chemical system that contains excess of one atom/molecule the polycrystals formed acts as a ‘seed’ over which more of the atoms/molecules bind together to grow the size to form a larger single crystal.