Final answer:
The properties of the orange liquid can be observed without changing it through visual inspection, density measurement, and spectroscopy, as these methods do not alter its chemical composition.
Step-by-step explanation:
The properties of the orange liquid can be observed without changing it by opting for methods that do not alter its chemical composition. Visual inspection, density measurement, and spectroscopy are key techniques for observing physical properties without inducing a chemical change. Visual inspection can reveal the liquid's color and state, density measurement can provide information on its mass-to-volume ratio, and spectroscopy can offer insights into its molecular composition.