Final answer:
The freezing point and density measurement are physical properties that can be observed to determine if a liquid is water. The freezing point of water is 0°C, and its density is approximately 1 g/cm³ at 4°C. These distinct and measurable physical properties make them reliable identifiers for water. The correct choices are B and D.
Step-by-step explanation:
To determine if a liquid is water, one can observe several physical properties. A useful property for identifying water is its freezing point, which is 0°C at standard atmospheric pressure. This characteristic is a widely used method for identifying substances because it is a unique and consistent physical property. Water's freezing point is particularly distinct and therefore useful for confirmation.
However, other physical properties like density measurement, color change, and smell could also give some indication about the liquid, but they are not as definitive as the freezing point because they can vary based on impurities or environmental conditions.
Density measurement is also a reliable physical property that can help to identify if a liquid is water. Water has a known density of approximately 1 gram per cubic centimeter (1 g/cm³) at 4°C. If the density of the given liquid closely matches this value, it can be an indicator that the liquid is indeed water. Other substances may have different densities, making this a helpful distinguishing characteristic.
These methods are based on the physical properties of substances, which include density, color, and freezing and boiling points. These properties can be observed or measured without changing the substance's chemical identity. The physical properties are distinct from chemical properties, which would describe a substance's ability to undergo a chemical change.
Hence, Options B and D are correct.