Explain what happens to the particles in a substance during a physical change.

Question: Explain what happens to the particles in a substance during a physical change.

During a physical change, the particles in a substance rearrange themselves, but their chemical composition remains the same. For example, when ice melts into water, the water molecules are still made up of two hydrogen atoms and one oxygen atom, but they are now moving more freely.

Here are some examples of physical changes:

• Melting ice
• Boiling water
• Evaporating alcohol
• Dissolving salt in water
• Crushing a rock
• Bending a metal wire

In each of these examples, the particles in the substance rearrange themselves, but their chemical composition remains the same.

Here is a more detailed explanation of what happens to the particles in a substance during a physical change:

• Melting: When a solid melts into a liquid, the particles in the solid break free from their fixed positions and start to move more freely. This is because the particles in a liquid have more kinetic energy than the particles in a solid.
• Boiling: When a liquid boils into a gas, the particles in the liquid gain enough kinetic energy to escape from the surface of the liquid and become a gas.
• Evaporating: Evaporation is a similar process to boiling, but it occurs at all temperatures, even below the boiling point. This is because some of the particles in a liquid always have enough kinetic energy to escape from the surface of the liquid.
• Dissolving: When a substance dissolves in another substance, the particles of the dissolved substance disperse throughout the particles of the solvent. The particles of the dissolved substance are surrounded by the particles of the solvent and are held in place by intermolecular forces.
• Crushing: When a solid is crushed, the particles in the solid are broken into smaller pieces. However, the particles themselves do not change their chemical composition.
• Bending: When a metal wire is bent, the particles in the wire are rearranged. However, the particles themselves do not change their chemical composition.

Physical changes are reversible, meaning that the substance can be changed back to its original state. For example, water can be frozen back into ice, and alcohol can be condensed back into a liquid.

Physical changes are important in many everyday processes. For example, we use physical changes to cook food, to clean our clothes, and to build things.