Physical changes

We need to determine whether ice melting into liquid water is a physical change or a chemical change, and why.

A physical change is one where the appearance or state changes but the chemical composition stays the same. In melting, the ice (solid H₂O) becomes water (liquid H₂O) — the substance is still water throughout.

During melting, the particles gain energy and move more freely, but no water molecule (H₂O) is broken apart or transformed into a different molecule. The chemical identity of water is preserved.

The correct answer is that it is a physical change because the water molecules (H₂O) are unchanged — only the state has changed. This directly matches the definition of a physical change.

We need to classify ice melting into water correctly and pick the option with the best scientific reasoning.

Ice has not 'disappeared' — it became liquid water. No new substance was created, so this cannot be a chemical change. Eliminate this option.

Heat does not destroy the bonds inside water molecules during melting. It only overcomes the attractive forces between molecules. This reasoning is scientifically incorrect. Eliminate this option.

A change in appearance alone does not make something a chemical change. Physical changes also alter appearance. Eliminate this option.

The remaining option — physical change because H₂O molecules are unchanged — is correct. This is accurate and uses proper scientific reasoning.

The question asks about the Moving Particle Theory and specifically what heating does to particles.

According to the Moving Particle Theory, heating a substance gives its particles more energy, which causes them to move faster. This is a fundamental principle of the theory.

The particles themselves do not grow in size, no new particles are created, and the forces of attraction are not permanently destroyed — they are simply overcome temporarily in changes of state.

The correct answer is: the particles gain energy and move faster. This is the core idea of how heating affects matter at the particle level.

We need to find the correct description of what happens to particles when a substance is heated, according to the Moving Particle Theory.

Heating does not make individual particles larger. The particles themselves stay the same size; they just move more. Eliminate this option.

The Moving Particle Theory states that particles are conserved — they are not created or destroyed by simply heating a substance. Eliminate this option.

Forces of attraction between particles are not permanently destroyed by heating. For example, steam can condense back into water, showing that attractive forces return when particles cool. Eliminate this option.

Particles gain energy and move faster is the correct answer — this is the fundamental effect of heating on particles according to the Moving Particle Theory.