HOT-WATER BALLOON

2 teaspoons of water, g-inch rubber balloon, microwave oven, oven mitt, safety glasses 

Put the balloon in the microwave oven and cook at full power for however many seconds it takes for boiling to begin, which is indicated by a rapid growth in the size of the balloon. It may take only about 

Remove the heated balloon with the oven mitt, shake the balloon around, and listen for the return of the liquid phase. You should be 

What happens if you submerge the inflated balloon in a pot of ice-cold water  

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A hot-water heating system forces water into pipes, or arrangements of pipes called registers that warm from contact with warm water. Air in the room warms from contact with the pipes. Usually, the pipes are on the floor of a room so that warmer, less dense air around the pipes rises somewhat like a helium-filled balloon rises in air. The warmer air cools as it mixes with cooler air near the ceiling and falls as its density increases. This process is called convection and the moving air is referred to as convection current. The process of convection described here is pipe-to-air and usually does a better job of heating evenly than in an air-to-air convection system—the circulation of air by fans as in a forced-air heating system. 

Use hot water from your sink faucet to fill a pan. Open one of the bottles of Coke. Quickly slip a balloon over the top of the bottle. Shake the bottle with the balloon over it. Set this bottle in the pan of hot water. NEVER HEAT A BOTTLE COVERED WTTH ANYTHING OTHER THAN A BALLOON. 

Open a bottle and cover it with a balloon. Put this bottle in the refrigerator. Open a second bottle and put it in a pan of hot water. The balloon on the bottle in the refrigerator should not get as large as the balloon on the bottle in the hot water. The cold temperature makes the molecules move slower and they are less likely to leave the liquid. We cap carbonated drinks and then put them in the refrigerator to keep them from losing carbon dioxide gas. 

If you take the same balloon and hold it under hot water for a period of time, the balloon s volume will increase. This happens because, as the helium atoms gain kinetic energy, they crash into the walls of the balloon faster, exerting more pressure on the inside of the balloon and causing it to expand. (You will learn much more about gases in Chapter 8.)... 

When you wash dishes with hot water, most of the water molecules are moving more rapidly than they do in cold water. They have more kinetic energy. Not all molecules of hot water in a sink have the same kinetic energy. They don t have the same speed. The same applies to a container of gas, such as an air-fQled balloon. AH the gas particles are moving randomly in the balloon at different rates. 

The hot air balloons are based on the principle of buoyancy. For example, a wooden spoon set free in the air falls down because its buoyancy is smaller than its mass (weight). In water, it is the opposite case the buoyancy is larger and the spoon floats. In hot air balloons the medium is always the same - air. We only change its density by changing its temperature. When the density of the air inside the balloon equals the density of the air outside, its buoyancy is zero and its net mass - 678 kg in this case - will prevent it from taking off. We have to make the air inside the balloon less dense by heating it up, e.g., using propane burners. 

Have you ever noticed that hot air rises You may have walked upstairs in your house and noticed it getting warmer. Or you may have witnessed a hot-air balloon take flight. The air that fills a hot-air balloon is warmed with a bimier, which then causes the balloon to rise in the cooler air aroxmd it. Why does hot air rise Hot air rises because the volume of a gas sample at constant pressure increases with increasing temperature. As long as the amount of gas (and therefore its mass) remains constant, wanning it decreases its density because density is mass divided by volume. A lower-density gas floats in a higher-density gas just as wood floats in water. 

On first consideration it may be thought that rubberiness is an invariant property, that rubber is rubber and that is all there is to it. On second thoughts one realizes that the number of products that can be made from natural rubber is very large and that the properties of such products may be very different. One has only to think of a tyre, a toy balloon, an ebonite battery box, an eraser, and a hot-water bottle to appreciate that considerable modification to the rubber may be made by judicious compounding. Indeed it may be argued that greater variation is possible by the selection of additives to the base rubber than by changing the base rubber. 

If you have ever seen a hot-air balloon aloft, you have seen a demonstration of how the density of a gas varies with temperature. Hot air is less dense than cold air, so hot air floats on cold air, much like oil floats on water. 

Gay-Lussac, Joseph Louis (1778 1850) A French chemist and physicist noted for his two laws on gases and for his work on alcohol-water mixtures. He was professor of physics at the Sorbonne and later took a chair of chemistry at the lardin des Plantes. Together with Jean-Baptiste Biot (1774-1862), he made the first-ever hot-air balloon ascent for scientific purposes in 1804, reaching an altimde of over 6 km. He is also credited with recognizing iodine as a new element and sujg esled the name lodo, with the codiscovery of boron, and the terms pipette and burettel... 

Gently agitate the second bottle in the same manner as in step 4. Then, place the bottle in a container of hot tap water for ten minutes. Measure the circumference of the balloon. 

The coolant flow area through the core is reduced in proportion to the deformation as the cladding balloons. The higher core resistance resulted in longer accumulator injection cycles due to the longer time required for accumulator water to reach the hot core surfaces and flash. The longer accumulator injections produced an earlier emptying of the accumulators than observed in Case 4. 

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