A chemical change results in the formation of a new substance. Example: igniting hydrogen in oxygen produces water. You can use these clues to determine a chemical change has occured: a colour change, a change in temperature, light and sound,bubbles beginning to form, solid/ semi solid precipitation form, and difficult to reverse it.
A physical change is just a change of state or form eg melting ice or grinding salt. physical change can be the bending, cutting ,breaking, dissolving a substance in water (H2o)