1.6- How does matter change its states?
As discussed above, matter can change its state. There are two ways to change the state of matter:
- By changing the temperature:-On increasing the temperature of any substance, the kinetic energy of the particles increase. Due to this, the particles start vibrating with greater speed and the heat energy overcomes the force of attraction between those particles. Thus, they start moving more freely and their state gets changed. For ex- Solids like ice gets melted on heating, acquiring liquid state and on further heating it turns into vapor, thus acquiring gaseous state.
- By changing the pressure: –By applying pressure, particles of matter can be brought close together. Also, applying temperature and reducing pressure can liquefy gases. For ex- The Liquefied Petroleum Gas (LPG) is filled into cylinders by applying pressure, due to which it gets liquefied. While using the LPG in cooking, the pressure gets reduced as it comes out and again takes the gaseous form.
1.7-Some important notes.
Here are some important points that you must look towards in the chapter before we move to the final topics:
- Melting point:-The temperature at which a solid melts to become a liquid at the given atmospheric pressure. It indicates the force of attraction between the particles of that matter.
- Fusion:–The process of change of solid state into the liquid state (melting).
- Latent heat:– The heat that gets absorbed by the particles of matter while changing from one form to another without showing any rise in its temperature is known as latent heat. The word latent means hidden. Actually, this heat gets used up while changing the form of matter.
- Latent heat of fusion:–Amount of heat energy required to change 1 kg of solid into liquid at the given atmospheric pressure at its melting point is known as the latent heat of fusion.
- Melting point of ice:–Melting point of ice is 0°C or 273 K (Kelvin). Water particles at 0°Chave more energy as latent heat as compared to ice particles at the same temperature.
- Boiling:–The process in which a liquid starts turning into a gas on heating. The liquid particles lose their force of attraction on heating and acquire gaseous state.
- Boiling point:–The temperature at which a liquid starts boiling at the given atmospheric pressure. Boiling is a bulk phenomenon as particles from the bulk of the liquid get required amount of energy for changing into gaseous state.
- Boiling point of water:–Boiling point of water is 100°C or 373 K.
- Latent heat of vaporization:–Amount of heat energy required to change 1kg of liquid into gaseous state at the given atmospheric pressure. Water vapour has more energy than water at the given temperature as the steam particles have absorbed extra energy in the form of latent heat during vaporization.
- Sublimation:– The change of state directly from solid state to gaseous state without turning into liquid state (or vice versa).
- Solid carbon dioxide/Dry ice:– The CO2gas when stored under high pressure turns into solid state known as Solid CO2 or Dry ice. It gets converted to liquid state on decreasing the pressure to 1 atm (atmosphere) without turning into liquid. That’s why it is also known as Dry ice.