Question

what do these two changes have in common?
newly poured concrete becoming hard
mixing chocolate syrup into milk
select all that apply.
both conserve mass.
both are changes of state.
both are caused by cooling.
both are chemical changes.

Explanation:

1. Both conserve mass: According to the law of conservation of mass, no matter is created or destroyed in physical or chemical changes, so both processes preserve total mass.
2. Both are changes of state: Concrete hardening is a transition from liquid to solid (physical change with setting), and mixing chocolate syrup (liquid) into milk (liquid) forms a homogeneous mixture, but more importantly, the concrete's state change and the syrup dispersing (a physical state-related change) fit this.
3. Incorrect options: Concrete hardening is not caused by cooling (it's a hydration reaction), and mixing syrup into milk is a physical change, not chemical.

Answer:

• Both conserve mass.
• Both are changes of state.