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Chapter 17: Problem 20

For food storage, what is the advantage of placing a metal lid on a glass jar? (Hint: Why does running the metal lid under hot water for a minute help you open such a jar?)

Short Answer

Expert verified
Question: Explain the advantage of using a metal lid on a glass jar for food storage and how running the metal lid under hot water can help open the jar. Answer: The advantage of using a metal lid on a glass jar for food storage is that it creates an airtight seal due to the higher rate of thermal expansion of metals, preventing the entry of air, contaminants, and microorganisms. Running the metal lid under hot water causes it to heat up and expand more than the glass, loosening the airtight seal and making it easier to open the jar.

Step by step solution

01

Identifying the materials and their properties

First, we need to identify the materials involved in this exercise: a metal lid and a glass jar. Metals generally have a higher rate of thermal expansion compared to glass. This means that metals expand more when heated and contract more when cooled compared to glass.
02

Understanding the advantage of a metal lid on a glass jar

Due to the higher rate of thermal expansion of metals, placing a metal lid on a glass jar creates an airtight seal as the metal lid contracts around the glass jar's opening when it cools down. This advantage prevents the entry of air, microorganisms, and any other contaminants, thus ensuring the food inside the jar is well-preserved.
03

Explaining the link between heating the metal lid and opening the jar

When the metal lid is placed under hot water, it heats up and expands. Since the metal expands more than the glass, loosening the airtight seal between the lid and the jar. This process makes it easier to open the jar, as it reduces the force required to break the seal between the lid and the jar.
04

Conclusion

In conclusion, the advantage of using a metal lid on a glass jar for food storage is the ability to create an airtight seal, which preserves the food inside by preventing the entry of contaminants. Running the metal lid under hot water helps to open the jar, as the expansion of the metal due to heating breaks the tight seal, thus making it easier to open.

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Most popular questions from this chapter

Two solid objects, \(A\) and \(B\), are in contact. In which case will thermal energy transfer from \(\mathrm{A}\) to \(\mathrm{B} ?\) a) \(\mathrm{A}\) is at \(20{ }^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(27{ }^{\circ} \mathrm{C}\) b) \(A\) is at \(15^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(15^{\circ} \mathrm{C}\). c) \(\mathrm{A}\) is at \(0{ }^{\circ} \mathrm{C},\) and \(\mathrm{B}\) is at \(-10{ }^{\circ} \mathrm{C}\).

A piece of dry ice (solid carbon dioxide) sitting in a classroom has a temperature of approximately \(-79^{\circ} \mathrm{C}\) a) What is this temperature in kelvins? b) What is this temperature in degrees Fahrenheit?

Suppose a bimetallic strip is constructed of two strips of metals with linear expansion coefficients \(\alpha_{1}\) and \(\alpha_{2}\), where \(\alpha_{1}>\alpha_{2}\) a) If the temperature of the bimetallic strip is reduced by \(\Delta T\), what way will the strip bend (toward the side made of metal 1 or the side made of metal 2)? Briefly explain. b) If the temperature is increased by \(\Delta T\), which way will the strip bend?

You are building a device for monitoring ultracold environments. Because the device will be used in environments where its temperature will change by \(200 .{ }^{\circ} \mathrm{C}\) in \(3.00 \mathrm{~s}\), it must have the ability to withstand thermal shock (rapid temperature changes). The volume of the device is \(5.00 \cdot 10^{-5} \mathrm{~m}^{3}\), and if the volume changes by \(1.00 \cdot 10^{-7} \mathrm{~m}^{3}\) in a time interval of \(5.00 \mathrm{~s}\), the device will crack and be rendered useless. What is the maximum volume expansion coefficient that the material you use to build the device can have?

In a thermometer manufacturing plant, a type of mercury thermometer is built at room temperature \(\left(20^{\circ} \mathrm{C}\right)\) to measure temperatures in the \(20^{\circ} \mathrm{C}\) to \(70^{\circ} \mathrm{C}\) range, with \(\mathrm{a}\) \(1-\mathrm{cm}^{3}\) spherical reservoir at the bottom and a \(0.5-\mathrm{mm}\) inner diameter expansion tube. The wall thickness of the reservoir and tube is negligible, and the \(20^{\circ} \mathrm{C}\) mark is at the junction between the spherical reservoir and the tube. The tubes and reservoirs are made of fused silica, a transparent glass form of \(\mathrm{SiO}_{2}\) that has a very low linear expansion coefficient \((\alpha=\) \(\left.0.4 \cdot 10^{-6}{ }^{\circ} \mathrm{C}^{-1}\right) .\) By mistake, the material used for one batch of thermometers was quartz, a transparent crystalline form of \(\mathrm{SiO}_{2}\) with a much higher linear expansion coefficient \(\left(\alpha=12.3 \cdot 10^{-6}{ }^{\circ} \mathrm{C}^{-1}\right) .\) Will the manufacturer have to scrap the batch, or will the thermometers work fine, within the expected uncertainty of \(5 \%\) in reading the temperature? The volume expansion coefficient of mercury is \(\beta=181 \cdot 10^{-6}{ }^{\circ} \mathrm{C}^{-1}\).
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