Answer to Question #180632 in General Chemistry for grayson

Question

4. Analysis of Data: Answer the following questions to compare your inference vs. the actual results of the activity.

a. When you drop granules of coffee into water, what happen to both substance?

b. When you drop powdered coffee into water, what happen to both substance?

c. When you drop dish washing liquid on water, what happen to both substance?

d. When you drop chunk of dish washing on water, what happen to both substance?

5. Conclusion: How will you explain the properties of liquid (water, dish washing liquid) and solids (coffee granules, coffee powder, dish washing paste) using the kinetic molecular model?

Answer 1

a. coffee granules, buoyed by gases formed in roasting, float when hot water is added

b. powdered coffee diffuses and mixes with the water. In hot water, diffusion takes a shorter time than in cold water.

c. The dishwashing liquid dissolves in the water and the all mixture turns to the colour of the dishwashing liquid. There's formation of foam. There's formation of more foam in hot water than in cold water.

d. The chunk of dishwashing soap settles at the bottom of the container without formation of any much foam compared to its liquid foam counterpart in c.

The kinetic molecular theory explains the behaviour of gases (in this case water particles) with different substances. This theory is based on the following postulates/assumptions.

1. Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.
2. These particles move in a straight line until they collide with another particle or the walls of the container.
3. These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space.
4. There is no force of attraction between gas particles or between the particles and the walls of the container.
5. Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container.
6. The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.

The kinetic molecular theory explains gas laws.

Gay-Lussac's Law (P is directly proportional to absolute T)

The last postulate of the kinetic molecular theory states that the average kinetic energy of a gas particle depends only on the temperature of the gas. Thus, the average kinetic energy of the gas particles increases as the gas becomes warmer. Because the mass of these particles is constant, their kinetic energy can only increase if the average velocity of the particles increases. The faster these particles are moving when they hit the wall, the greater the force they exert on the wall. Since the force per collision becomes larger as the temperature increases, the pressure of the gas must increase as well

Boyle's Law (P = 1/v)

Gases can be compressed because most of the volume of a gas is empty space. If we compress a gas without changing its temperature, the average kinetic energy of the gas particles stays the same. There is no change in the speed with which the particles move, but the container is smaller. Thus, the particles travel from one end of the container to the other in a shorter period of time. This means that they hit the walls more often. Any increase in the frequency of collisions with the walls must lead to an increase in the pressure of the gas. Thus, the pressure of a gas becomes larger as the volume of the gas becomes smaller

Charles' Law (Volume  occupied by a fixed amount of gas is directly proportional to Temperature at constant pressure )

The average kinetic energy of the particles in a gas is proportional to the temperature of the gas. Because the mass of these particles is constant, the particles must move faster as the gas becomes warmer. If they move faster, the particles will exert a greater force on the container each time they hit the walls, which leads to an increase in the pressure of the gas. If the walls of the container are flexible, it will expand until the pressure of the gas once more balances the pressure of the atmosphere. The volume of the gas therefore becomes larger as the temperature of the gas increases.

Graham states that the rates at which gases diffuse is inversely proportional to the square root of their densities (Graham's law of diffusion)