Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-27

An alloy is a material that is made by combining a metal with at least one other element. While the (35) __________ component is usually a metal, the other elements can be either metals or non-metals. The purpose of creating an alloy is to produce a new substance which has improved characteristics compared to its individual components. Essentially, an alloy is a special mixture designed for better performance.

Pure metals often have limitations. For example, pure iron rusts easily and pure aluminum is quite soft. By mixing them with other elements, we can create alloys with more (36) __________ properties. Stainless steel, for instance, is an alloy of iron and chromium and is known (37) __________ its powerful resistance to rust. Similarly, adding copper to aluminum creates duralumin, a much stronger and harder material which is used in aircraft construction.

The process of creating an alloy is technically demanding. First, the component metals (38) __________ melted at very high temperatures in a large furnace. This is a process (39) __________ requires extreme heat and careful control. Once the metals are in a liquid state, they are mixed together in very precise proportions. The specific amount of each component is critical because it determines the final properties of the alloy. Finally, the liquid mixture is allowed to cool and solidify, forming the new material.

There are thousands of different alloys used in our daily lives. Bronze, an alloy of copper and tin, was one of the first alloys ever created by humans and was used for tools and weapons. (40) __________, steel is arguably the most important alloy today, essential for building everything from skyscrapers to cars. (41) __________ different types of steel exist, each designed for a specific purpose, such as surgical steel for medical instruments or high-carbon steel for durable tools.

In conclusion, alloys are a fundamental part of modern materials science. By carefully blending different elements, we can engineer materials that are stronger, lighter, or more resistant to corrosion than their original forms. As technology advances, new alloys are constantly being developed, and they continue to (42) __________ a crucial role in industrial progress.

When you buy a cup of milk tea or iced coffee in Vietnam today, you'll likely notice something different. Many popular cafes have stopped using plastic straws, offering paper, bamboo, or metal ones instead. This shift isn't just happening here; it's part of a global movement against single-use plastics, encouraged by government policies like Directive No. 33/CT-TTg. But while saying 'no' to a plastic straw feels like a good deed, it raises an important question: are these small changes truly helping our planet, or are they more for show?

The campaign against plastic straws gained popularity because it addresses a visible and relatable problem. Horrifying images of sea turtles with straws stuck in their noses went viral, making millions of people aware of the dangers of plastic waste in our oceans. For environmental groups, the plastic straw is an ideal target. It is not an essential item for most people, making it an easy thing to give up. In this context, refusing a plastic straw has become a powerful, symbolic act, representing a person's commitment to environmental protection and raising awareness of the larger issue of plastic pollution.

However, critics argue that the intense focus on straws is a distraction from bigger environmental threats. Statistically, plastic straws make up a very small fraction of the total plastic waste in the ocean—less than 1%. A far more significant problem is abandoned fishing gear, such as nets and lines, which constitutes a much larger percentage of marine debris and is far more deadly to sea life. By concentrating so heavily on straws, we may be ignoring these more damaging sources of pollution and giving ourselves a false sense of accomplishment.

Furthermore, the alternatives to plastic straws are not without their own problems. Paper straws often become soft and unusable quickly, and if they are contaminated with liquid, they usually cannot be recycled. Reusable straws, like those made from metal or silicone, require water and energy to be cleaned after every use. Some studies even suggest that certain alternatives might have a larger carbon footprint to produce than the plastic straws they replace, considering the entire lifecycle from manufacturing to disposal.

Ultimately, the war on plastic straws is complicated. While it may not be the magic solution to cleaning our oceans, its greatest value might be in starting a global conversation. It has forced consumers and companies to think more critically about our throwaway culture. The small act of choosing a different straw can be a gateway to bigger, more impactful changes, but only if we recognize it as a first step, not a final destination in the journey toward a healthier planet.