Chapter 15: Properties of Liquids (and 13)
The picture below shows droplets of acetone and water. (The droplet of acetone is smaller than water) What properties of acetone can you infer in relation to water? (Discuss vapor pressure, boiling point, volatility, and surface tension (adhesion/cohesion)
Vapour pressure of liquids increase as you increase temperature. The vapour pressure of acetone is expected to be higher than the vapour pressure of water because the intermolecular forces in acetone are weaker (no hydrogen bond force) which means that they move around more freely than water molecules which allows them to vaporize easier.
What is a volatile substance Example
Volatile: something that evaporates really easily. Ex- nail polish remover.
Formation of meniscus for water Relate this to IMF and attractions
When liquid water is in a tube, it's surface (meniscus), has a concave shape because water wets the surface and move up the sides. Water wants to have IMF with silicon that the glass is made out of. It is attracted to it.
How are boiling and volatility related Therefore, which one will be more likely to evaporate at a lower room temperature
The more volatile the substance is, the lower the boiling point is whereas a less volatile substance has a higher boiling point. A volatile substance is more likely to evaporate at a lower or room temperature, but for this to happen it needs to have enough vapor pressure.
The picture below shows droplets of acetone and water. What properties of acetone can you infer in relation to water? The acetone drop is smaller than water. (Discuss vapor pressure, boiling point, volatility, and surface tension (adhesion/cohesion)
Vapor pressure of liquids increase as you increase temperature. The vapor pressure of acetone is expected to be higher than the vapor pressure of water because the intermolecular forces in acetone are weaker (no hydrogen bond force) which means that they move around more freely than water molecules which allows them to vaporize easier.
What is vapor pressure When is the pressure greater
Vapor pressure: the pressure of a vapor in contact with its liquid or solid form. The greater the collisions, the greater the pressure.
How does temperature affect vapor pressure As the temperature of a liquid increases... As the kinetic energy of the molecules increases...
As the temperature of a liquid increases, the kinetic energy of its molecules also increases. As the kinetic energy of the molecules increases, the number of molecules transitioning into a vapor also increases, which increases the vapor pressure. Vapor pressure will increase with an increase in temperature.
How does vapor pressure indicate volatility What is a volatile substance What is the pattern Ex- water has a low vapor pressure Diethyl ether has a high vapor pressure What will the volatility be and WHY
At every single temperature, water will have less vapor pressure than diethyl ether. • Diethyl ether is more volatile, because it is turning into a gas more easily because of the high vapor pressure. • The stronger IMF's will go with the ones that tend to be liquids (it wants to stick together) , meaning that it will have the lowest vapor pressure.
What does boiling point depend on? How does this relate to a pressure cooker
Boiling point of water depends on the air pressure. If the boiling point of the water increases, the foods cooking time will decrease. The air that is kept up by the sealed lid of the pressure cooker will cause the food quicker. It gets a lot hotter.
Define boiling point and evaporation.
Boiling point: the temperature at which a liquid boils to vapor. Evaporation: The process of turning from liquid to vapor.
Differences between boiling point and evaporation
Boiling takes place within the whole liquid and always at the same temperature, called the boiling point, whereas evaporation occurs only at the surface of a liquid and can occur at any temperature but is increased by weaker intermolecular forces or a higher temperature. Boiling point: Boiling is a phase transition from the liquid phase that occurs at or above the boiling temperature. When boiling happens, particles change from liquid to gas throughout the whole liquid. Evaporation: It may occur when the partial pressure of vapor of a substance is less than the equilibrium vapour pressure. When evaporation happens, particles only change to a gas at the surface.
If the molecules are more attracted to each other, then the substance will have a____ boiling point If the molecules are less attracted to each other, then it will have a____ boiling point
Higher Lower
Similarities between boiling point and evaporation
In both situations the form of a liquid takes the form of a gas or vapor. Both result in a phase change.
Formation of meniscus for mercury Relate this to IMF and attractions
Mercury doesn't wet the glass- the cohesive forces within the drops are stronger than the adhesive forces between the drops and glass. When liquid mercury is in a tube, it's surface (meniscus) has a convex shape because the cohesive forces in liquid mercury tend to make it into a drop. Mercury isn't attracted to silicon, it is attracted to itself. It will create a little convex bubble.
Relate intermolecular forces to surface tension What is surface tension Does mercury or water have a greater surface tension and what does this explain Cohesion
Stronger intermolecular forces will produce greater surface tension. Surface tension: measured as energy required to increase the surface area of a liquid by a unit of area. Mercury has a greater surface tension due to the metallic bonds and stronger intermolecular forces than water. This is why it will not be attracted to the sides of the silicon like water is. Cohesion: the intermolecular attraction between like molecules.
Discuss vapor pressure in acetone VS water Boiling point of acetone VS water Volatility of acetone VS water Surface tension of acetone VS water
The vapor pressure in acetone is higher than water because the smaller particle size makes acetone easier to evaporate (less volume). The boiling point of acetone is lower than water because there is less surface area for the heat to be spread out to, and water has stronger hydrogen bonds. Acetone has higher volatility because of its weak intermolecular forces, which allows liquid to turn to gas with little energy. Water has a higher surface tension because it can form stronger intermolecular forces (hydrogen bonds).
When will boiling take place in relation to vapor pressure What two pressures are involved in this in boiling What are boiling points based off of
The water molecules are pushing or pulling against the air molecules. When vapor pressure equals atmospheric pressure, boiling will take place. Boiling will happen by either increasing the vapor or atmospheric pressure until they are equal. Boiling points are based off of how strongly the molecules are attracted to each other. It is based on the intermolecular attractions and forces (IMF'S)
What happens with nonpolar solute with nonpolar solvent What compound should not dissolve in water
Water is polar. Polar and ionic will dissolve in water. Nonpolar will not dissolve in water. C4 H10 is nonpolar
What temperature will water boil under normal atmospheric pressure At higher altitudes will it take more or less energy to boil water and why What temperature will water boil at Mount Everest Will the altitude change cause the food to cook faster or slower and why
Water will boil at 100 degrees C (212 degrees F) under normal atmospheric pressure. However, at higher altitudes, it will take less energy to boil water because there is less pressure. At the top of Mount Everest, water can boil at just 72 degrees C (161.6 degrees F). Cooking involves heating a food to a certain temperature for a certain length of time. If the temperature is lowered because of altitude (as in the case of boiling water), cooking time will have to be extended to complete the cooking process.
Explain why pasta would take longer to cook at the top of Mount Everest than in your home. First, think about what atmospheric pressure is caused by What happens to the particles as you move farther away from earth- what does this mean about the pressure
We learned in chapter 14 that atmospheric pressure is caused by collisions of air particles. The further you go away from earth, the more gravity weakens, causing there to be fewer particles at higher altitudes. Since there is a fewer number of particles, there will be less collisions, causing the atmospheric pressure to decrease as altitude increases.
How are vapor pressure and volatility related
A volatile substance has a high vapor pressure at a given temperature compared with a nonvolatile compound, which has a low vapor pressure. Volatile: Having relatively high vapor pressures and low boiling points.
Why does water have a concave meniscus while mercury has a convex meniscus? (in terms of interparticle forces) Concave VS Convex
Concave Meniscus: having an outline or surface that curves inward like the interior of a circle or sphere. Convex Meniscus: having an outline or surface curved upward like the exterior of a circle or sphere.
What is an example of vapor pressure
Ex- manometer. If the atmospheric and gas pressure are the same, then there will be no vapor pressure. Higher atmospheric pressure means more vapor pressure in the gas.
Explain why pasta would cook faster in a pressure cooker than in a pot on your stovetop. Relate this to pressure, temperature, boiling point
Food cooks faster in a pressure cooker because it traps steam from boiling the cooking liquid and causes the internal temperature and pressure to raise quickly. The higher pressure causes the boiling point of water to increase. Higher temperature of water means higher transfer of heat to the food being kept in it. This will cause it to cook faster.
• FLIP OVER The water will have the stickiest particles, meaning that it will have the strongest IMF attraction and the highest boiling point. • Stronger IMF's, needs a higher temperature and more kinetic energy to break away from liquid and for its particles to escape.
What is the normal pressure that a liquid boils at Why is the boiling point of water so high compared to the other compounds on the chart
What steam hits your skin, what happens Relate this to energy Latent heat of vaporization
When steam (water in gas phase) hits your skin, a lot of energy will be released as it condensed into a liquid, undergoing a phase change. The loss of energy that is released from steam hitting your skin occurs quickly and in a small localized area, therefore causing damage to your cells. Latent heat of vaporization: the amount of heat energy required to change a unit of mass into liquid vapor.
What do these measurements indicate about interparticle forces in volatile substances
When the molecules in a liquid have enough kinetic energy, they can escape and go into the gas phase, this is known as vapor pressure. The higher the vapor pressure, the weaker the IM forces will be. The higher the volatility, the weaker IM forces will be because they need to break apart to form the gas.
Why is a burn from steam more severe than one from an equal mass of boiling water? Phase change VS temperature change- relate this to energy Heat of vaporization
When water goes from gas to liquid, it is undergoing what is called a phase change. Phase changes require a lot more energy than just a temperature change. The energy required for water to go from a liquid to a gas is called the heat of vaporization.
Why does acetone look flattened out on a table and water beads up on a table What properties of acetone can you infer in relation to water Vapor pressure, boiling point, volatility
• If you drop a bunch of magnets onto a desk top, they are going to clump together. This is what the water will do. The forces will clump like magnets. It will have stronger IMF's. • The acetone is like marbles, they don't have attractions. This means that it will flatten out. It will have the weaker IMF. It will have a lot more evaporated particles. ◦ This means that there are less collisions, which means that there is more vapor pressure because the vapor particles will be trying to escape faster. ◦ It also means that it will have a low boiling point because it wants to evaporate and separate from the other particles. ◦ It also means that it will have a higher volatility since it is able to evaporate easily because the particles are not as attracted to eachother.
