| INSTRUMENTS FOR DEMONSTRATION OF THERMAL EXPANSION LIQUID 1. Take two identical flask of 50-100 cm 3 and rubber stoppers, tightly fitting the neck flasks. Each tube is passed through a glass tube with an inner diameter of 4-5 mm and a length of not less than 400 mm. In one flask to the top pour tinted water, and in another - stained alcohol or denatured alcohol, and alcohol and water should be painted in different colors so that when an experiment could be easier to observe the thermal expansion of liquids. If you close the flask stopper, the excess fluid will result in part through the edge of the bottle, and partly to rise in a glass tube, which should not be issued from the tube inside the bulb. Need to ensure that the level of liquids in both tubes was the same height. On each glass tube put a small rubber ring at 2-3 mm below the liquid level. One of the bulbs should be put in a container with hot water. At the initial level of liquid in the tube drops. It's easy to see, as the fluid is below the rubber ring. Why is this happening? Lowering the level of the liquid due to the fact that the walls of the flask from heat immediately expand and increase the volume of the flask and the liquid is so fast no time to warm up, so its level in the tube due to the rapid growth of the bulb first few drops. The liquid is then heated in a flask, and its level in the tube increases rapidly. This shows that the thermal expansion coefficient of liquids more than solids (glass). If the vessel with hot water to omit both the bulb, then after some time the level of alcohol in the tube will be higher than the water level in the second flask. Consequently, at the same heating to the same temperature, some liquid expands more than others. Different liquids have different thermal expansion coefficient. 2. We need to take iron pipe with a diameter of 50-60 mm and a height of 200-250 mm in the lateral surface of her to make two round holes, one near the top edge and the second as close as possible to the bottom of the tube. Plugged tubes and passed them through the thermometers. Tube should cover the hole is very tight so that water does not seep out of the tube. After removing the tube, the tube pushed onto the railway bank, for example, from the cans, solder it to the middle of the tube, and in the bottom of the cans punched a nail or drilled holes, so that got a sieve. Closing the side openings in the tube caps, fill it with water having room temperature, and in a tin can put pieces of ice. At first, thermometers show the same temperature. Then lower the thermometer will show a lower temperature than the upper, since the cooling water is compressed and sinks to the bottom. But it will last only as long as the water temperature reaches 4 ° C. From this point on, the upper thermometer will indicate the temperature below 4 ° C, while the lower thermometer readings do not change. This suggests that the water at 4 ° C has the highest density. It is important that students are in the process of manufacturing devices is well understood that they are made and why. Then they become a natural tendency to enter a particular improvement or improvements in device design, to manufacture the device more intuitive, easy to use. This will encourage independence of thought, the development of creative initiative. |