Comparing the boil time for a copper and steel kettle

In summary: If you touch a glass mug of hot water, you can hold it for a few minutes before it starts to feel warm. So, based on that, maybe the reason the water takes less time to boil in the copper kettle is because of the increased thermal conductivity of copper.
  • #1
gijoel
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Homework Statement


Your friend prefers to use a glass kettle with a copper base. You notice that the water takes less time to boil when using this kettle compare to the stainless steel one. Explain the phenomenon behind this observation.

Homework Equations

The Attempt at a Solution



1. Heat is directly conducted from the base of the kettle to the water inside. The amount of heat that passes through the kettle base depends on the thermal conductivity of the material of the base. The thermal conductivity of an object is defined as “how many Watts of heat can be conducted through a one meter thickness of said material with a one Kelvin temperature difference between the two ends.” (Koolance, n.d.) giving a unit of W/(mK).

The thermal conductivity of copper is 401 W/(mk) and stainless steel is 16.3. Whilst glass’ thermal conductivity is 1.2 – 1.4. Thus copper conducts heat 25.1 times better than stainless steel, so more heat will flow through it for a given amount of time than stainless steel. Because glass’ thermal conductivity is approximately 286 times lower than copper the heat inside the kettle is trapped. Causing the water’s temperature to climb faster.

References:

Koolance, n.d., "Cooling 101: The Basics of Heat Transfer", viewed 20 August 2015, <http://koolance.com/cooling101-heat-transfer> .
 
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  • #2
And your question is?
 
  • #3
Am I right? The lecturer is being a pain in the butt and vague on her questions. Plus she hasn't really covered thermal conductivity but has done specific heat capacity
 
  • #4
gijoel said:
Am I right? The lecturer is being a pain in the butt and vague on her questions. Plus she hasn't really covered thermal conductivity but has done specific heat capacity

Physics is concerned with the real world, you know. So, maybe you could answer a question like this using your knowledge of the real world. You probably have a reasonable grasp of thermal conductivity from knowing that: you can hold a mug filled with hot water, but not a glass for very long and if you touch a metal kettle or pan filled with hot water, you'll burn yourself instantly.
 

1. What is the difference in boil time between a copper and steel kettle?

The difference in boil time between a copper and steel kettle depends on several factors, such as the material thickness, heat conductivity, and heating source. Generally, copper kettles have a higher heat conductivity, which allows them to heat up faster than steel kettles. However, steel kettles may have a thicker material, which can retain heat for a longer period of time, resulting in a longer boil time.

2. Why is there a difference in boil time between copper and steel kettles?

The main reason for the difference in boil time between copper and steel kettles is due to their varying heat conductivities. Copper is a better conductor of heat compared to steel, meaning it can transfer heat more efficiently. This allows the water in a copper kettle to heat up faster, resulting in a shorter boil time.

3. Does the type of heating source affect the boil time for copper and steel kettles?

Yes, the type of heating source can affect the boil time for copper and steel kettles. For example, if both kettles are placed on a gas stove, the copper kettle will heat up faster due to its higher heat conductivity. However, if both kettles are placed on an electric stove, the steel kettle may have a shorter boil time due to its thicker material and ability to retain heat.

4. Can the shape and size of the kettle affect the boil time?

Yes, the shape and size of the kettle can also affect the boil time. A smaller and more compact kettle will have a faster boil time compared to a larger and wider one. This is because the water molecules in a smaller kettle are closer together, allowing for more efficient heat transfer. Additionally, a kettle with a wider base may have a shorter boil time compared to one with a narrow base, as it allows for more surface area to be in contact with the heat source.

5. Are there any other factors that can influence the boil time for copper and steel kettles?

Yes, there are a few other factors that can influence the boil time for copper and steel kettles. These include the initial temperature of the water, the altitude at which the kettles are being used, and the presence of impurities in the water. These factors can affect the efficiency of heat transfer and therefore impact the boil time for both types of kettles.

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