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        <img post-id="1481" fifu-featured="1" width="1200" src="https://i2.wp.com/assets.iflscience.com/assets/articleNo/78117/aImg/82243/thermos-meta.png?w=1200&resize=1200,0&ssl=1" class="attachment-post-thumbnail size-post-thumbnail wp-post-image" alt="How Does A Thermos Keep Hot Drinks Hot And Cold Drinks Cold?" title="How Does A Thermos Keep Hot Drinks Hot And Cold Drinks Cold?" decoding="async"/><br />
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        <p>Have you ever come across the classic joke about a thermos that manages to keep hot beverages hot and cold ones cold? The punchline is amusingly perplexing, asking, “But how does it know?” While it’s a humorous thought, the reality is that thermoses don’t possess any kind of awareness. The more intriguing question is: what mechanisms allow thermoses to maintain temperature?</p><br />
        <p>To understand this, we can travel back to the late 1800s when the Scottish chemist and physicist James Dewar was embarked on a quest to study liquid oxygen, which boils at a frigid -183°C (-297°F). Dewar needed a reliable way to keep this substance cool long enough for thorough experimentation. This is where the principles of thermodynamics come into play.</p><br />
        <p>The second law of thermodynamics states that heat naturally flows from warmer areas to cooler ones. Consequently, to keep substances at either high or low temperatures, it’s essential to slow down this heat transfer process. This is where Dewar’s brilliant invention comes into action.</p><br />
        <p>Dewar devised a straightforward yet clever solution: he nested one flask inside another, creating a near-vacuum space between them. This vacuum effectively curtails heat transfer via conduction and convection, while a reflective surface within the flask diminishes heat loss through radiation. As a result, this innovative design excels at maintaining the temperature of its contents by minimizing heat exchange with the external environment.</p><br />
        <p>The next time you relish a steaming cup of coffee or a comforting meal from your thermos, take a moment to appreciate the science at work. It’s not just a magical feat that keeps your food and drinks at the right temperature; it’s the smart application of thermodynamics by pioneers like James Dewar that makes it all possible.</p><br />
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