Changes of State

What happens when matter changes state?

         A change of state is the change of substance from one physical form of matter to another. When a substance experiences a physical change, it does not change its identity, just its appearance. In order to change a substance from one state to another, energy must be added or moved. While a substance gains or loses energy, its temperature or state changes. The temperature and state do not change at the same time because the temperature does not change till after the change of state.

         Matter is made of tiny particles that are in constant motion. The motion of the particles changes in the middle of a change of state. Particles can break away from each other and gain more freedom to move like when a solid changes to a liquid, or vice versa. The particles can also attract each other more strongly, and have less freedom to move. For example, when gas changes to a liquid, or a liquid changes to a solid. During a change of state, a substance must gain energy from the environment or loss energy to the environment while maintaining the total amount of energy preserved. Like a water cycle, each change of state represents a transfer of energy either into or out from the surrounding environment. But energy is never created or destroyed.

How do solids and liquids change states?

         Particles in a liquid can slide past each other, yet particles in a solid can only move enough to vibrate. By removing energy from a liquid can cause it to change to a solid. Adding energy to a solid can cause it to change to a liquid. It is called freezing when the change of state changes a liquid to a solid. The liquid has to be at freezing point in order for the substance can change into a solid. The change of state in which changes a solid to a liquid is called melting and the temperature at which the substance changes from a solid to a liquid is called the melting point.

How do liquids and gases change state?

         Particles in a gas have a great deal of energy. When removing enough energy from a gas causes a gas to change a liquid or a solid and adding enough energy to a liquid or a solid causes it to change into a gas. This process is called vaporization. Vaporization can happen in three different ways: evaporation, boiling and condensation. Evaporation occurs when a liquid gets warmed slowly and the higher the temperature the faster the liquid turns to gas. A rapid change from a liquid to a gas is called boiling and it has to be at a specific temperature in order for this to occur which is called the boiling point. The greater the air pressure, the higher the boiling point of a liquid. Condensation is the reverse of evaporation. This is the change of state from a gas to a liquid.

How do solids and gases change state?

Some solids and gases can change state without ever becoming a liquid, which can only occur in sublimation and deposition. The change from a solid to a gas is called sublimation. As the particles of solid dry ice gain energy their motion overcomes the attraction making the particles escape into the air as gas. Deposition is the change of state from a gas to a solid. This can only happen when ice crystals form in clouds.

What happened to matter when a change of state occurs?

         Matter changes from one state to another; it remains the same kind of matter. Its physical state changes, but its chemical identity does not. It makes it a change of state because the energy, movement, and the distance between the particles changes. The mass of a substance does not change when its state changes, making each state contain the same amount of matter.

Yesenia Gomez