Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-73

How do we define a 'day'? On Earth, we think of it as 24 hours. However, the scientific definition is a bit more specific. A day on any planet is the amount of time it takes for that planet to (35) __________ one complete time on its axis. This is known as a sidereal day. The time it takes for a planet to finish (36) __________ one full circle determines the length of its day.

Every planet spins on (37) __________ imaginary line called its axis, which runs through its center from the North Pole to the South Pole. (38) __________ understand this better, imagine a spinning top. Just like the top, a planet's rotation creates the cycle of day and night. The side of the planet facing its star experiences daytime, while the opposite side is in darkness, experiencing nighttime.

Not all planets spin at the same speed. For example, Earth completes one rotation in about 24 hours. In contrast, Jupiter spins very quickly, completing a rotation in just under 10 hours. Early astronomers reported that Jupiter (39) __________ much faster than Earth. Venus, on the other hand, rotates incredibly slowly; one day on Venus is longer than its entire year!

The speed of rotation has a significant impact on a planet's climate and environment. If a planet spun very slowly, its days and nights (40) __________ extremely long. This would cause extreme temperature differences between the day and night sides. Scientists had to (41) __________ the different rotation speeds for each planet using advanced telescopes and calculations to understand these effects.

Therefore, defining a 'day' is not as simple as just saying '24 hours'. It's a fundamental concept in astronomy that depends entirely on a planet's unique rotation. Studying these differences is fascinating, and for astronomers who research celestial mechanics, it's all (42) __________.

Anyone living in a hot, humid climate like Vietnam's understands the daily struggle to stay cool and comfortable. For generations, the go-to solutions have been lightweight, natural fabrics like cotton and linen. While these materials are breathable, they often absorb sweat and become heavy and damp, sticking uncomfortably to the skin. But what if our clothes could do more than just cover us? What if they could actively help us cool down? This is no longer science fiction; it's the cutting edge of material science.

Scientists are developing innovative fabrics engineered with specific cooling properties. One of the most promising approaches is 'radiative cooling'. All objects, including our bodies, release heat in the form of infrared radiation. Traditional fabrics trap this heat close to the skin. Radiative cooling textiles, however, are designed to be transparent to this infrared radiation, allowing body heat to escape directly into the environment. Another popular technology is advanced moisture-wicking. Unlike cotton which simply absorbs moisture, these synthetic fabrics pull sweat away from the skin to the outer surface of the garment, where it can evaporate quickly. This process of evaporation is what creates a powerful cooling sensation.

Creating these high-tech textiles involves sophisticated engineering. For instance, some radiative cooling fabrics are made from nano-porous polyethylene—a material similar to plastic wrap but filled with microscopic pores that let heat out while blocking visible light. Other fabrics might have their fibers coated with special nanoparticles. They are often more expensive to produce than traditional textiles and face challenges in matching the soft, natural feel of cotton. However, as research progresses, scientists are finding ways to improve their texture and reduce production costs, making them more practical for everyday use.

This wave of innovation is particularly relevant for Vietnam's booming textile industry. To compete on the global stage, many local companies are shifting their focus from mass production to creating high-value products with advanced features. We can already see this trend in the local market. Brands like Coolmate have gained immense popularity among young Vietnamese consumers by focusing specifically on technology-enhanced basics, such as t-shirts and underwear made from moisture-wicking materials. Their success proves there is a strong demand for clothing that offers a scientific solution to the discomfort of a tropical climate.

The development of cooling fabrics represents a significant leap forward in how we think about clothing. No longer just a matter of fashion or modesty, our garments are becoming functional tools to enhance our daily comfort and well-being. As these technologies become more widespread and affordable, the sweaty, sticky feeling of a hot day could soon become a thing of the past.