- A stopwatch is used to measure time
- How long something takes to happen is a kind of measurement of time
- So, a stopwatch can be used to measure how long something takes to happen

- A stopwatch can be used to measure how long something takes to happen
- A process takes time to happen
- So, a stopwatch can be used to measure how long a process takes to happen

- A stopwatch can be used to measure how long a process takes to happen
- Melting is a kind of process
- So, a stopwatch can be used to measure how long it takes for melting to happen

So, a stopwatch can be used to measure how long it takes for melting to happen
Question: Which tool is used to determine how long it takes warm water to melt an ice cube?
Context: - A process takes time to happen 
- A stopwatch is used to measure time 
- Melting is a kind of process 
- How long something takes to happen is a kind of measurement of time