A reaction vessel that is completely sealed and the Earth would be my answers. This is because the matter inside of these systems is not exchanged anywhere but inside itself. (the glass flask could count, but the not insulated thing might be why it doesn’t count)
It is harmful because you can get burned easy and your clothes can get dirty.
Answer:

Explanation:
Hello,
In this case, the increase in the temperature involves the addition of heat that is defined in terms of mass, heat capacity and temperature:

In this case, the heat capacity of iron is 0.450 J/(g*K), thus the heat results:

In such a way, since the temperature is increased heat is added, that is why it is positive.
Best regards.
Answer:
Matter is the term for any type of material. Matter is anything that has mass and takes up space. At a minimum, matter requires at least one subatomic particle, although most matter consists of atoms.
Some examples are: Water, books, pencils, sun, earth, moon, electron, proton, mesons, and quarks
Answer:
As you used two diferent instruments, one is more sensitive than the other.
Explanation:
The sensitivity of an instrument is the minimum amount of magnitude that can be differentiate a measurement system.
In method A, you got 27 cm, so if in method B, you got 27.00, method B is more sensitive. It's like saying that one system measures more than the other