Water bath. Experiment.

Simple heat transfer experiment using what is known as a "Marie Bath".
The bain-marie, commonly known as "water bath" in English, is a culinary technique used to gently heat or cool liquid or solid foods by submerging the container holding them into another larger container filled with hot or cold water, respectively. This method provides gentle and even heating or cooling, avoiding direct contact with the heat source and reducing the risk of burning or overcooling the foods.
In the culinary world, the bain-marie is commonly employed to prepare dishes that require gentle and controlled temperatures, such as sauces, custards, puddings, and chocolates. It is also useful for melting heat-sensitive ingredients like chocolate and butter without scorching them.
Beyond its culinary applications, the bain-marie is also utilized in laboratories to heat or cool substances in a controlled manner, especially those sensitive to abrupt temperature changes. This technique is prevalent in scientific research as well as in the pharmaceutical and food industries, where it is employed for sterilization and pasteurization processes.
In summary, the bain-marie is a versatile technique used in both culinary and laboratory settings to provide gentle and uniform heating or cooling of foods and substances, allowing for precise temperature control and preserving the quality of the final products.