Mass is not conserved in chemical reactions. Mass is therefore never conserved because a little of it turns into energy in every reaction
C unbalanced force is occuring
Both mass and weight are measured by using scales.
Explanation:
Yes, a chemical reaction can happen with only one substance.
A typical example of such reaction is the radioactive decay.
Radioactive decay is the loss of elementary particles from an unstable nucleus, ultimately changing the unstable element into another more stable element. .
When radioactive elements are let alone, they decompose to form stable harmless elements.
An example of radioactive decay is attached in the image below;