Which of the following statements is true? 1. A testable questions does not include an independent variable or a dependent variable.
2. A testable question should state the dependent variable but not the independent variable.
3. A testable question should state the independent variable but not the dependent variable.
4. A testable question should state both the independent variable and the dependent variable.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.

a chemical change results in a new substance being formed; whereas a physical change will result in a different state of matter

explanation: