If a substance has a density greater than water, what happens when it is placed in water?

If a substance has a density greater than water, what happens when it is placed in water?

• A. It will sink.
• B. It will float.
• C. It will stay at the surface.
• D. It will dissolve.

Answer: (A)

When a substance is denser than water, its weight per unit volume exceeds the weight of the water it would displace. The buoyant force from the water can only support a weight equal to the displaced water; since the object's weight is greater, the net force points downward. That causes the object to sink rather than float at the surface. It will continue sinking until it can no longer displace more water or it reaches the bottom. If an object were less dense than water, it would float because the buoyant force could balance or exceed its weight.

When a substance is denser than water, its weight per unit volume exceeds the weight of the water it would displace. The buoyant force from the water can only support a weight equal to the displaced water; since the object's weight is greater, the net force points downward. That causes the object to sink rather than float at the surface. It will continue sinking until it can no longer displace more water or it reaches the bottom. If an object were less dense than water, it would float because the buoyant force could balance or exceed its weight.