Changes of State

Depending on the temperature, a substance can exist in one of three states: solid, liquid, or gas

For example, at room temperature, water is a liquid. However, when heated, it turns into water vapour, which is a gas. When water is put in a freezer, the temperature decreases, so it turns into ice, which is a solid.

Physical changes don’t alter the substance or its particles, which remain the same across all three states; only their arrangement and movement differ.

Matter can transition between states, and there are five different types of state changes, which you can see below.

Melting: This is the process that changes a solid to a liquid. When a solid is heated, the particles begin to vibrate as they gain more energy. This weakens the forces between the particles.

BoilingOtherwise known as vaporisation, this process changes a liquid to a gas. As mentioned, adding heat to a liquid will cause the particles to vibrate and move around even more. This also causes the bonds between the particles to break, forming a gas.

CondensationThis process changes a gas to a liquid. To go from a gas to a liquid, the gas needs to be cooled. This causes bonds to form between the particles, which causes liquid formation.

FreezingThis process changes a liquid to a solid. To freeze a liquid, you need to cool it, which leads to bond formation between particles.

Sublimation: Under certain conditions, a solid can turn into a gas. An example of this is the sublimation of iodine.

Materials store internal energy. When a substance is heated, its internal energy increases. and when its cooled, its internal energy decreases.

Conservation of Mass

When a substance changes state, the mass does not change. Only the arrangement, closeness, and motion of the particles change. This is known as the conservation of mass.

For example, 10 grams of water will evaporate to form 10 grams of water vapour.

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