Understand Boyle's Law. Click on the link to Watch VIDEO explanation: Watch Video
Do this activity. Take a deep breath, hold on, count 5 and then breath out. Why did the chest expand while we inhale and why did it contracts while we exhales. That's Boyle's law in action. In this module we learn about Boyle's law that concerns about the relationship between pressure and volume of a gas. Air is a gas. Gas has several properties that can be observed with our senses. The gas pressure, temperature, mass and volume are variables that are related to one another. Let us observe what happens when volume and pressure are the variables and temperature and mass of gas are constant. You have a cylinder with a fixed amount of dry gas at constant temperature i.e. the mass and temperature of gas are constant. The pressure of gas is 4 atm. Observe the volume occupied. Click on weights to reduce the pressure on cylinder. The pressure is now 2 atm. Observe the volume of gas in the cylinder. It has doubled. Reduce the pressure to 1atm. The volume has again doubled. As the pressure is successively halved, the volume doubled. As the pressure reduced the volume increased. Thus volume is inversely proportional to the pressure and the product of pressure and volume is a constant. Mathematically, P*V=k, where V is the volume and k is the Boltzmann constant, k=1.38 * 10^-23 and P is the pressure. Here is another activity to understand relationship between and pressure and volume of a gas confined held at constant temperature. The syringe contains a fixed no. of moles of a gas at constant temperature. It is air tight and fixed to a pressure gauge. When plunger is dragged, the volume of gas varies in the syringe. In the mid 1600 studied the relationship between the pressure P and volume V of a confined gas held at a constant temperature. Boyle's observed that at given temperature the volume of a confined gas with constant mass is inversely proportional to its pressure. The product of pressure and volume is nearly constant at constant temperature i.e. PV=k where k is the Boltzmann constant. At constant temperature let a given mass of gas occupy Volume V1 at pressure P1 and volume V2 at pressure P2. So mathematically P1V1=P2V2. Remember you can use any unit of volume and pressure as long they remain same throughout calculation. This relationship is called Boyle's law in his honour. Now solve a conceptual example. You are at beach resort at sea level. You buy a balloon filled with helium of 4.5L. Atmospheric pressure 100KPa. What will be the volume at pressure of 50KPa. Assume temperature remains constant. It is common knowledge that gases are highly pressurised to make them compact. The action of syringe is another practical application of Boyle's law. When we draw fluids inside syringe, we increase volume inside syringe, decrease pressure inside while the pressure outside is greater. This imbalance forces the fluid inside the syringe. If we reverse the action and put the plunger in, the volume inside is decreased, increasing the inside pressure than outside pressure and fluids are forced out. It can be used to explain the mechanics of breathing. When we breath in air the chest wall expands, increasing the volume of chest cavity. When the diaphragm rises the chest wall contracts reducing the volume of chest cavity thereby expelling the air. This brings about inspiration and expiration. When a vessel containing soap solution agitated bubbles at the bottom of the vessel are seen to increase in volume as they rise gradually to the surface. Why so?
Do this activity. Take a deep breath, hold on, count 5 and then breath out. Why did the chest expand while we inhale and why did it contracts while we exhales. That's Boyle's law in action. In this module we learn about Boyle's law that concerns about the relationship between pressure and volume of a gas. Air is a gas. Gas has several properties that can be observed with our senses. The gas pressure, temperature, mass and volume are variables that are related to one another. Let us observe what happens when volume and pressure are the variables and temperature and mass of gas are constant. You have a cylinder with a fixed amount of dry gas at constant temperature i.e. the mass and temperature of gas are constant. The pressure of gas is 4 atm. Observe the volume occupied. Click on weights to reduce the pressure on cylinder. The pressure is now 2 atm. Observe the volume of gas in the cylinder. It has doubled. Reduce the pressure to 1atm. The volume has again doubled. As the pressure is successively halved, the volume doubled. As the pressure reduced the volume increased. Thus volume is inversely proportional to the pressure and the product of pressure and volume is a constant. Mathematically, P*V=k, where V is the volume and k is the Boltzmann constant, k=1.38 * 10^-23 and P is the pressure. Here is another activity to understand relationship between and pressure and volume of a gas confined held at constant temperature. The syringe contains a fixed no. of moles of a gas at constant temperature. It is air tight and fixed to a pressure gauge. When plunger is dragged, the volume of gas varies in the syringe. In the mid 1600 studied the relationship between the pressure P and volume V of a confined gas held at a constant temperature. Boyle's observed that at given temperature the volume of a confined gas with constant mass is inversely proportional to its pressure. The product of pressure and volume is nearly constant at constant temperature i.e. PV=k where k is the Boltzmann constant. At constant temperature let a given mass of gas occupy Volume V1 at pressure P1 and volume V2 at pressure P2. So mathematically P1V1=P2V2. Remember you can use any unit of volume and pressure as long they remain same throughout calculation. This relationship is called Boyle's law in his honour. Now solve a conceptual example. You are at beach resort at sea level. You buy a balloon filled with helium of 4.5L. Atmospheric pressure 100KPa. What will be the volume at pressure of 50KPa. Assume temperature remains constant. It is common knowledge that gases are highly pressurised to make them compact. The action of syringe is another practical application of Boyle's law. When we draw fluids inside syringe, we increase volume inside syringe, decrease pressure inside while the pressure outside is greater. This imbalance forces the fluid inside the syringe. If we reverse the action and put the plunger in, the volume inside is decreased, increasing the inside pressure than outside pressure and fluids are forced out. It can be used to explain the mechanics of breathing. When we breath in air the chest wall expands, increasing the volume of chest cavity. When the diaphragm rises the chest wall contracts reducing the volume of chest cavity thereby expelling the air. This brings about inspiration and expiration. When a vessel containing soap solution agitated bubbles at the bottom of the vessel are seen to increase in volume as they rise gradually to the surface. Why so?
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