this part insulates the reaction chamber from the transfer of heat to or from the surrounding environment…

this part insulates the reaction chamber from the transfer of heat to or from the surrounding environment. this part contains a known amount of water, which is placed there before the experiment starts. this part is where the metal is placed at the beginning of the experiment. this part is used for measuring the initial and final temperatures of the water.
Answer
Explanation:
Step1: Identify thermometer
A is a thermometer and is used for measuring temperature, so the part for measuring initial and final temperatures of water is A.
Step2: Identify water - containing part
C contains the water placed before the experiment starts as it is the inner - most container where water can be held.
Step3: Identify metal - placement part
The metal is placed in C at the beginning of the experiment as it is the reaction space within the apparatus.
Step4: Identify insulating part
B is the outer - most part which insulates the reaction chamber from heat transfer with the surroundings.
Answer:
Insulating part: B Part with known - amount of water: C Part where metal is placed: C Part for measuring temperature: A