Explanation:

An object with a density of 0.5gcm3 would float in water. This is because the object is less dense than water and will therefore experience a buoyant force that is greater than its weight. The buoyant force is the upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In this case, the fluid is water and the object is the substance with a density of 0.5gcm3. The buoyant force is equal to the weight of the water displaced by the object. Since the object is less dense than water, it will displace more water than it weighs and the buoyant force will be greater than its weight. This will cause the object to float.