MATTER AND ITS STATES IN CHEMISTRY
When you look around, you see many things like plants, animals, land, water, rocks, different objects like desk, chair, book, pen, bag, shoes, houses, cars, etc. But have you wondered what makes up plants and animals? What makes up land and water? What makes up desk and chair? The answer to all of these questions is matter? Everything in the Universe, from the tiniest particle of dust to the biggest star, is made up of matter. This matter occurs in four states or forms – solid, liquid, gas and plasma. So, the matter is not only what we can see or touch but, it also includes the air we breathe in, perfume we smell, etc. Therefore, we can say that all physical substances which we can see, touch, smell or feel around us are matter.
The scientific definition of matter for kids –
The matter is anything which occupies space and has a mass.
In my post “What is an atom?” we learned that atom is the main building block of all things around us. However, it will be interesting for you to know that even atoms and other subatomic particles are made of matter.
CAN MATTER BE CREATED?
The Universe consists of two things – matter and energy. Most scientists believe that matter and energy are the same things and each can convert into the other. During Big-Bang at the time of the creation of the Universe, a great amount of energy was evolved. Then just after a few seconds, some bundles of energy turned into tiny particles of matter. These tiny particles combined with each other to form atoms that made up the Universe in which we live today. All the matter created during Big-Bang still exists. It can be as huge as a planet or a star, or as small an atom – or even as tiny as the subatomic particles.
FOUR STATES OF MATTERS
Since ancient times, people believed that matter exists only in three states or forms – solid, liquid and gas. However, this changed in the 1920s with the discovery of the fourth state of matter – plasma. Plasma is a very uncommon state of matter. It exists only at incredibly high temperatures, in nuclear reactors, or inside stars.
Sometimes, the same matter can exist in three different states. For example, water is a liquid normally; if we fill it an ice tray and keep it in the freezer for some time, it becomes solid (ice). The same water, when boiled for some time, changes into gas (steam). Although, each state of matter has its own features and properties. But the atoms and molecules in the matter do not change for each different state. When a substance changes from one state to another, without a change in its chemical composition, is called interconversion of state of matter.
We can explain the different state of matter on the basis of the arrangement of particles or molecules in it. The molecule of any kind of matter always attracts each other with a force – an intermolecular force. The force of attraction between two molecules increases, if the space between them decreases and vice-versa. The space between the molecules is called intermolecular space.
The molecules of matter are always in random motion because they possess kinetic energy. The kinetic energy increases with temperature and vice-versa. Due to random motion, the molecule sometimes comes closer and sometimes move apart.
In solids, the molecules are very close to each other. There is a strong force of attraction between the molecules and the space between them is very small (almost negligible). The molecules are, therefore, not free to move. They merely vibrate at their positions. This makes solids hard and difficult to compress, giving them a fixed shape and size.
In the case of liquids, the molecules are not as close to each other as in solids. They also do not attract each other as strongly as the molecules of solids. Thus the spaces between them are larger and molecules are able to move about more freely. This makes a liquid flow and takes the shape of the container into which it is poured. Thus, liquids have fixed volume but no definite shape of their own.
In cases of gases, the molecules hardly attract each other. They lie far apart from each other and space are, therefore, very large. The force of attraction is so weak that the molecules have great freedom to move. As a result, gases have neither a fixed shape nor a fixed volume. They completely fill up the space available to them. The can be easily compressed as well, thus decreasing the gaps between them.
Plasma unlike other three states of matter is not made of atoms or molecules. It is a state of matter, which is somewhat like a gas but its properties are significantly different from that of gas. In plasma, atoms lose electrons and become positive, while the electrons move freely. Basically, it is electrically neutral gas with both positively and negatively charged particles (ions) moving freely in the same space. Plasma is a very uncommon state of matter. It exists only at incredibly high temperatures, in nuclear reactors, or inside stars. As per scientist 99% of the matter in the Universe is plasma.
Comparison between properties of Solids, Liquids, and Gases
|1||Intermolecular Space||Molecules are closely packed.||More space in comparison to solid.||Molecules are far apart from each other.|
|2||Intermolecular forces||Very strong.||Not as strong as in solids.||Negligible.|
|3||Shape||Have fixed shape.||Have no fixed shape. They take the shape of the container.||Have no fixed shape. They take the shape of the container.|
|4||Volume||Have fixed volume.||Have fixed volume.||Have no fixed volume.|
|5||Fluidity||Do not flow.||Flow from a higher level to a lower level.||Flow in all directions.|
|6||Effect of pressure i.e. compression||No effect of pressure.||Effect of pressure is low. Slightly compressible.||Effect of pressure is high. Highly compressible.|
INTERCONVERSION OF STATES OF MATTER
The same matter or substance can change state, from solid to liquid, or from liquid to gas and vice-versa. In everyday life, we come across substances that change from one state to another. For example, water is a liquid under normal condition, but when cooled it turns into ice. This happens because during cooling we remove kinetic energy from molecules of water in the form of heat. This increases the force of attraction between the molecules and brings them closer to form ice, a solid. Contrary to this, when we heat water, it starts boiling and turns into steam. During boiling, we provide kinetic energy to the molecules of water in the form of heat. This weakens the intermolecular force of attraction between molecules and they fly further apart from each other in the form of steam, a gas.
Similarly, steam on cooling turns into liquid water, and so does ice when kept at room temperature. But the properties of water remain the same in all the three states.
Some terms related to interconversion of state of matters
- Melting or Fusion: It is a process by which a substance changes from solid to liquid state on heating.
- Melting Point: It is the temperature at which pure substance changes from solid to liquid state.
- Vapourization or Evaporation: It is a process by which a substance changes from liquid to gases state on heating at any temperature.
- Boiling: It is a process by which a substance changes from liquid to gases state on heating at the fixed temperature.
- Boiling point: It is the temperature at which pure substance changes from liquid to gases state.
- Condensation or liquefaction: It is a process by which a substance changes from gases to liquid state on cooling at a fixed temperature.
- Solidification or freezing: It is a process by which a substance changes from liquid to solid state on cooling