- Increasing heat causes thermal expansion
- As the heat of an object increases , the mass of the object will stay the same
- Therefore, the mass of object will stay the same during thermal expansion caused by increasing heat

- The mass of object will stay the same during thermal expansion caused by increasing heat
- Objects are made of substances
- Hence, the mass of substance will stay the same during thermal expansion caused by increasing heat

So, the mass of substance will stay the same during thermal expansion caused by increasing heat
Q: Which of the following properties of a substance is conserved during thermal expansion?
Context:
- Objects are made of substances 
- Increasing heat causes thermal expansion 
- As the heat of an object increases , the mass of the object will stay the same