Simple Tests:

* Appearance: Water is typically clear, colorless, and odorless.

* Taste: Water has a neutral taste. Be careful, though, as some substances may look and smell like water but are dangerous to taste.

* Boiling point: Pure water boils at 100°C (212°F) at standard atmospheric pressure. You can heat a small sample of the substance and observe if it boils at this temperature.

* Freezing point: Pure water freezes at 0°C (32°F). You can place a small sample in a freezer and see if it turns solid at this temperature.

More Advanced Tests:

* Conductivity: Pure water is a poor conductor of electricity. You can use a conductivity meter to test the substance. However, impurities like salts can make water more conductive.

* pH test: Pure water has a neutral pH of 7. You can use pH paper or a pH meter to test the substance.

* Density: The density of water is 1 gram per cubic centimeter (g/cm³). You can measure the density of the substance and compare it to this value.

Important Considerations:

* Safety: Be cautious when testing unknown substances. Some may be dangerous or harmful.

* Accuracy: Simple tests may not always be accurate, especially if the substance is contaminated or has impurities.

* Professional Testing: If you need a definitive answer, it's best to consult a chemist or laboratory for professional analysis.

Remember, the best way to determine if a substance is water is to use a combination of tests and to exercise caution when dealing with unknown substances.