Make a Crossbow with Rubber Bands

We use many things made of rubber, like rubber bands, rubber gloves, tires, erasers, and rain boots. Rubber has a property called ① which means it stretches when you pull it and goes back to its original shape when you let go. It is also soft, easy to bend, waterproof, and does not conduct electricity, so it is great for many different uses. Do you know how rubber is made? If you cut the trunk of a ② , which grows in tropical regions, white sap comes out, like in the picture. When this sap is dried and hardened, it becomes raw rubber. A long time ago, people in South and Central America used raw rubber to make bouncy balls. They also used it for waterproofing things like shoes, pots, and clothes by spreading the rubber on them. Christopher Columbus, who discovered the Americas, was the first person to introduce rubber to Europe. He saw the native people of on the island Haiti playing with balls that bounced well. Amazed by the material’s elasticity, he introduced rubber to Europe. However, natural rubber has some problems. It is easily affected by temperature changes. when it gets hot, it melts, smells bad, and becomes sticky. When it gets cold, it gets hard and cracks. So, it was mostly used for things like erasers and toys. ③ , an American, believed that rubber could become a very useful material if its weaknesses were fixed. He did many experiments by mixing rubber with other materials to make a new kind of rubber. In 1839, he accidentally dropped a mix of rubber and sulfur onto a stove. He discovered that, unlike natural rubber, this new rubber kept its elasticity even when heated. This process is called  ④ . Vulcanized rubber has better elasticity and can be used for a long time, even when the temperature changes. After Charles Goodyear died, a tire and rubber company named after him was founded in 1898, and it is still operating today. Today, not only natural and vulcanized rubber, but also synthetic rubber made in different ways is used.