Question

in general, when a substance changes from a solid to a liquid,

a. the substance no longer has density since density is a property only solids have.

b. the density of the substance remains the same.

c. the density of the substance increases.

d. the density of the substance decreases.

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Explanation:

Step1: Recall the formula for density

Density ($
ho$) is given by the formula $
ho=\frac{m}{V}$, where $m$ is mass and $V$ is volume.

Step2: Analyze the change in volume during phase change from solid to liquid

When a substance changes from a solid to a liquid, its mass ($m$) remains constant (assuming no evaporation or other mass - loss processes). However, in general, the volume ($V$) of the substance increases. For example, consider ice (solid) and water (liquid). Ice has a crystalline structure with more empty space in some cases compared to the liquid state (for water, this is a special case, but in general for most substances).

Step3: Use the density formula to find the effect on density

Since $
ho=\frac{m}{V}$ and $m$ is constant and $V$ increases, using the property of fractions (if the numerator is constant and the denominator increases, the value of the fraction decreases), we can say that $
ho$ (density) decreases.

Answer:

D. the density of the substance decreases.