Chemistry ch. 10 bookwork

pg. 351 #1-7 Why is a water molecule polar?

(1) The differing electronegativities between its components: oxygen is much more electronegative than hydrogen, so a hydrogen-oxygen bond will be polar (2) The bent structure: all bent molecules are polar

Describe the arrangement of molecules in liquid water and in ice.

-Liquid water: hydrogen bonding; no definite structure; can fill any shape; relatively dense -Ice: hydrogen bonding; rigid hexagonal structure; water molecules are much farther apart than in liquid water; makes less dense than liquid water

Why does ice float? Why is this phenomenon important?

-floats on water because it is less dense than water due to molecules being far apart in its structure -important in the cases of large bodies of water

Compare and contrast the 4 types of crystals.

1) Metallic crystals- atoms are joined together by metallic bond, crystals are very hard. 2) Ionic crystals- solids that contain ionic bond in their structure consist of ionic crystals, crystals re brittle 3) Covalent crystals- solid substances in which atoms are held together by covalent bond are known as covalent crystals. 4) Molecular crystals- molecules are joined together by weak Van Der Wall forces, these substances have low melting point and boiling point.

Which of the following gases would you expect to deviate significantly from ideal behavior: He, O2, H2, H2O, N2, HCl, or NH3?

HCl, H2O, and NH3 are the most polar of these, so they won't behave ideally because the particles have greater attractive forces between them.

Describe the conditions under which a real gas is most likely to behave ideally.

High temperature, low pressure - the molecules in a real gas are far apart and exert little force among themselves.

Is more energy required to melt one gram of ice at 0C or to boil one gram of water 100C? How do you know?

More energy is required to boil water, water boils at a high temperatures, high temperature means more energy, ice melts at low temperatures, low temperature means less energy is required.

pg. 341 #1-6 Describe the solid state according to the kinetic molecular theory.

Particles are more closely packed, but still moving Intermolecular forces much more effective due to relatively fixed positions More ordered than liquids or gases

Explain why ionic crystals melt at much higher temperatures than typical covalent molecular crystals?

Stronger bonds

Molecules of hydrogen escape from Earth, but molecules of oxygen and nitrogen are held to the surface and remain in the atmosphere. Explain.

The amount of gravity is dependent on the amount of mass. Hydrogen is very light, which enables it to leave the atmosphere.

How does the kinetic-molecular theory explain the pressure exerted by gases?

The greater the number of molecules, the greater the number of collisions with the walls off the container at a constant temperature, and the greater the pressure of the gas, and vice-versa. Particles are always in motion and when they are contained, they are elastic collisions.

What is the equilibrium vapor pressure of a liquid?

The pressure exerted by the vapor in equilibrium with its liquid at a certain temperature

What happens to gas particles when a gas is compressed?

They get closer together, if enough pressure is put on the gas in closed environment, it will increase in heat which will cause more kinetic energy and eventually particles will not be able to float past each other (becomes liquid). Their volume increases.

In the phase diagram for water, what is meant by the triple point and the critical point?

Triple point: indicates the temperature and pressure conditions at which the solid, liquid, and vapor coexist at equilibrium Critical point: critical temperature and critical pressure

Compare vaporization and evaporation.

Vaporization: below boiling point Evaporation: at/above boiling point

Why is exposure to steam dangerous?

When steam (water in the gas phase) hits your skin, a lot of energy will be released as it condenses 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

How does the kinetic-molecular theory explain the following properties of liquids: (a) relatively high density, (b) ability to diffuse, and (c) ability to evaporate?

a. Relatively high density due to close arrangement b. Diffusion is slower due to particles being closer together and attractive forces slowing movement c. Higher force of attraction, higher surface tension

Why is ice less dense than liquid water?

water molecules are much farther apart in ice than liquid making ice less dense

What would be an example of deposition?

Gas to a solid, the reverse of sublimation, dry ice

pg. 348 #1-7 What is equilibrium?

A dynamic position in which two opposing processes occur at equal rates in a closed system

How is the structure of water responsible for some of water's unique characteristics?

-Cohesion and ability to fill its container: due to hydrogen bonding -Solid more dense than liquid: due to rigid hexagonal structure in which the molecules are relatively far apart from each other

pg. 336 #1-6 Describe the liquid state according to the kinetic-molecular theory.

According to the kinetic-molecular theory of liquids, the particles are not bound together in fixed positions; instead they move about constantly giving them their fluidity

Why do crystalline solids shatter into regularly shaped fragments when broken?

Already in geometric shape

What happens to the liquid vapor system at equilibrium if the temperature is increased? What happens to this system if the temperature is decreased?

The liquid molecules at the surface start to become vapor, then the vapor molecules start to become liquid again

The evaporation of liquid water from the surface of earth is an important step in the water cycle. how do water molecules obtain enough kinetic energy to escape into the gas state?

The particles start to move faster and overcome the intermolecular forces that bind them to liquids, this allows them to escape.

List the properties of liquids.

1- Liquids have a high density relative to gases. Their density is about 1000 x that of the gas of the same substance. 2- Liquids are relatively not compressible. 3- Liquids have the ability to diffuse. 4- Liquids exhibit surface tension, a force that tends to pull adjacent parts of a liquid's surface together, thereby decreasing the surface area to its smallest possible size. Surface tension resists penetration of objects into a liquid. 5- Liquids have capillary action, the attraction of the surface of a liquid to the surface of a solid.

What is the difference between an amorphous solid and a crystalline solid?

Crystalline - Geometric shape Amorphous - No definite shape

Explain why liquids in a test tube form a meniscus.

If the liquid is attracted to the glass, it's pulled upward into the test tube creating a concave surface. A liquid will rise high in a narrow tube and will wet the tube is a strong attraction exists between the liquid molecules and the tube attraction pulls the liquid upward along the surface of the tube and against the force of gravity.

What is the boiling point of a liquid?

The temperature at which the vapor pressure equals atmospheric pressure

pg. 332 #1-7 Use the kinetic-molecular theory to explain each of the following properties of gases: expansion, fluidity, low density, compressibility, and diffusion.

Expansion: The molecules are moving in continuous straight lines. So they will continue in one direction until colliding with something, meaning they will fill whatever container they are in. Fluidity: Fluidity is the ability to flow, or move from one place to another. Since gases are in constant motion, and the molecules are independent of each other, the gas is able to flow. Low Density: The molecules are much further apart than with a solid or liquid. Density for a gas is 1/1000 the density of the same substance in the liquid or solid phase, because the particles are so far apart. Compression ability: Gases can be compressed because there is so much space between molecules. Due to the elastic collision, they are always bouncing off the containers walls- when the space gets smaller, the particles move faster. Diffusion: Diffusion is movement from an area of high concentration to an area of low concentration. When gas particles are mixed randomly, the particles continue to move throughout the available space.

What happens to gas particles when a gas is heated?

It behaves more like an ideal gas, the particles move farther apart, there are more collisions between the particles, the particles start moving faster (If volume is kept constant this will cause an increase in pressure too). Their velocity increases - the particles move around more quickly.

Account for each of the following properties of solids: (a) the definite volume, (b) the relatively high density of solids, (c) the extremely low rate of diffusion.

a. Definite volume because particles are packed closely together therefore there is little room for compression b. High density and incompressibility Substances most dense in solid state Slightly denser than liquids; much denser than gases due to particles being much more closely packed C. Low rate of diffusion

Refer to the phase diagram to answer the following questions: a. Describe all the phase changes a sample of solid water would undergo when heated to its critical temperature at a pressure of 1.00 atm. b. Describe all the phase changes a sample of water vapor would undergo when cooled to 5C at a pressure of 1.00 atm. c. At approximately what pressure will water be a vapor at 0C? d. Within what range of pressures will water be a liquid at temperatures above its normal boiling point?

a. No phase changes - water vapor is a gas with a minimum temperature of 100ºC at 1.00 atm, and undergoes no phase changes as it is heated to 373.99 ºC (maybe melting and evaporating?) b. condensing c. .006atm d. 1 to 217.75atm