Topic 4 Topic 4-Phases of Matter Phases of Matter

Topic 4-Phases of Matter Phases of Matter 6. Gas Laws a. Solid a. Boyle’s Law b. Liquid b. Charles’ Law c. Gas c. Gay-Lussac’s Law Heating/Cooling Curves d. Combined Gas Law a. Potential energy Use Table T b. Kinetic energy c. Sublimation and Deposition 7. Kinetic-Molecular Theory Temperature Scales (KMT) a. Kelvin b. Celsius 8. Ideal Gas vs. Real Gas c. Use Formula on Table T Heat vs. Temperature 9. Filtration *know the difference Measuring Heat Energy 10. Distillation a. Heat of Fusion-Table B b. Heat of Vaporization-Table B 11. Chromatography c. Specific Heat of Water-Table B d. Use Formulas on Table T

Properties of Solids 1. Definite shape 6. Particles are packed tightly together, often in an orderly arrangement 2. Definite volume 3. Incompressible 4. Expand only slightly when heated 5. Particles vibrate around a fixed point

Properties of Liquids Indefinite shape-take shape of container 2. Definite volume 3. Arrangement of particles is not orderly or rigid 4. Almost incompressible. 5. Expand slightly when heated 6. Particles are free to flow

Properties of Gases 1. Indefinite shape 2. Indefinite volume 3. Expands to fill the entire container 4. Easily compressible 5. Particles are far apart from each other

3 Phases of Matter Some people claim there is a 4th phase of matter called: Plasma The three normal phases of matter have been known for many years. In recent times, we have begun to study matter at the very high temperatures and pressures which typically occur on the Sun, or during re-entry from space. Under these conditions, the atoms themselves begin to break down; electrons are stripped from their orbit around the nucleus leaving a positively charged ion behind. The resulting mixture of neutral atoms, free electrons, and charged ions is called a plasma.

A term used for substances, like oxygen, that exist Gas vs. Vapor What is the difference? Gas- A term used for substances, like oxygen, that exist in the gaseous state at room temperature Vapor- Describes the gaseous state of a substance that is generally a liquid or solid at room temperature Water in the gaseous state is a vapor because at room temperature, it is a liquid Oxygen in the gaseous state is a gas because at room temperature, it is a gas

The phase changes from: S  L  g  plasma Are all endothermic Endothermic-describes a physical change or chemical reaction that absorbs heat energy

Most substances go through all three phase changes: Exothermic: g  L  s (heat/energy released) Or Endothermic: S  L  g (heat/energy absorbed) BUT: Some substances like to skip a phase

Sublimation- The process in which a solid changes to a gas or vapor without passing through the liquid state The process in which a gas or vapor changes to a solid without passing through the liquid state Deposition- Two substances which these terms apply to are: 1. Dry ice (carbon dioxide)-CO2 2. Iodine (I2)

Temperature-the property or condition of a body that determines the direction of heat flow between it and another body. It is a measure of the AVERAGE KINETIC ENERGY (KE) of the molecules As temperature increases, so does average KE As temperature decreases, so does average KE If temperature remains the same (RTS) so does average KE

The energy stored in a bond Potential Energy the energy of a body or a system with respect to the arrangement of the particles of the system The energy stored in a bond As temperature increases = PE remains the same As temperature decreases = PE remains the same

Calorimetry- Precise measurement of the heat flow into or out of a system for chemical and physical processes Even though there are five areas on a cooling or heating curve, there are only three equations: 1. Q = mc T-when temperature changes 2. Q = mHf-when substance melts or freezes 3. Q = mHv-when substance boils or condenses

How much energy is needed to raise the temperature of 500 g of water at 30 C to 70 C? Notice: no phase change just temperature change Only need Q = mc T Q = (500)(4.18)(40) Q = 83600 joules

How much energy is needed to melt 60 g of ice at 0 C? Just a phase change: melting/fusion no temperature change Only need one equation: Q = mHf Q = (60)(334) 20040 joules

How much energy is needed to raise the temperature of 10 g of ice at -23 C to water at 50 C? Notice: temperature change & phase change Q = mc T Raise the temperature from -23 to 0 C Q = (10)(2.09)(23) = 480.7 joules Now make the phase change Q = mHf Q = (10)(334) = 3340 joules Now raise the temperature from 0 to 50 C Q = mc T Q = (10)(4.18)(50) = 2090 joules Add the 3 numbers: 480.7 + 3340 + 2090 = 5910.7 joules

How much energy is needed to raise 50g of water at 50 C to steam at 115 C? There is a phase change and a temperature change 1. Raise temperature from 50 to 100 C Q = mc T Q = (50)(4.18)(50) = 10450 joules 2. Vaporize the water Q = mHv Q = (50)(2260) = 113000 joules 3. Raise the temperature from 100 to 115 Q = mc T Q = (50)(2.09)(15) = 1567.5 joules Add them up: 125017.5 joules

Temperature Temperature- AVERAGE KINETIC ENERGY Is a measure of how hot or cold something is. An object’s temperature determines the direction of heat transfer. Heat ALWAYS moves from an area of high temperature to low temperature

Scientists commonly use two equivalent units of temperature, the degree Celsius and the kelvin Anders Celsius (1701-1744) freezing point of water = 0 C boiling point of water = 100 C The distance between these two fixed points is divided into 100 equal intervals Lord Kelvin (1824-1907) freezing point of water = 273 K boiling point of water = 373 K The distance between these two fixed points is divided into 100 equal intervals

A change of one degree on the Celsius scale is equivalent to one kelvin on the Kelvin Scale To convert between the scales, use Table T K = C + 273 C = K - 273 or

Notice that for ANY temperature scale, there are two fixed points: Freezing point and boiling point Also: The freezing point = melting point of any substance Water freezes at 0 C and melts at 0 C So if you know the melting point of a substance, you also know the freezing point Table S lists the melting point of all the elements so you also know the freezing point of all the elements

The zero point on the Kelvin temperature 0 K = absolute zero Absolute zero- The zero point on the Kelvin temperature scale, equivalent to -273.15 C At absolute zero, all molecular motion stops

A measure of the force exerted by a gas above a liquid Vapor Pressure A measure of the force exerted by a gas above a liquid in a sealed container; a dynamic equilibrium exists between the vapor and the liquid Temperature has nothing to do with boiling. Pressure determines when a substance boils

The temperature at which the vapor Boiling point- The temperature at which the vapor pressure of a liquid is equal to the atmospheric pressure on the liquid Normal boiling point- Boiling point of a liquid at a pressure of 101.3 kPa (standard pressure)

Low bp = high vapor pressure High bp = low vapor pressure Low bp = weak intermolecular forces (IMFs) High bp = strong intermolecular forces (IMFs) Low bp = high vp = weak IMFs High bp = low vp = strong IMFs

Energy that transfers from one object to another Heat Energy that transfers from one object to another because of a temperature difference between the objects Law of Conservation of Energy The heat released by the system is equal to the heat absorbed by the surroundings. Conversely, the heat absorbed by a system is equal to the heat released by its surroundings.

3 Factors that Affect the Behavior of Gases 1. temperature 2. pressure 3. volume A small change in any of these factors causes a huge change in the behavior of the gas. 3 scientists studied the behavior of gases by holding one of the variables constant and adjusting the other two variables.

Standard Temperature & Pressure (STP) 0 C 273 K Pressure 1 atm 101.3 kPa 760 torr 760 mm Hg These can be found on Table A

Boyle’s Law Robert Boyle 1627-1691 Held temperature constant Varied pressure & volume volume Pressure = Pressure = volume Indirect/inverse relationship

Boyle’s Law

A balloon contains 30 L of helium gas at 103 kPa. Boyle’s Law Equation V1P1 = V2P2 You can use any units of volume and pressure as long as they are the same on both sides A balloon contains 30 L of helium gas at 103 kPa. What is the volume of the helium when the balloon rises to an altitude where the pressure is only 25 kPa Temperature is not mentioned so we know it is constant V1P1 = V2P2 (30)(103) = (x)(25) X = 123.6 L

Charles’ Law Jacques Charles 1746-1823 Held pressure constant Temp = volume Temp = volume Direct Relationship

Charles’ Law

What temperature in Celsius is need to change 50 mL of Charles’ Law Equation V1 = V2 T1 T2 *temperature MUST be in Kelvin What temperature in Celsius is need to change 50 mL of a gas at 37 C to 200 mL? 50 mL = 200 mL 310 K x X = 1240 K Which equals 967 C

Gay-Lussac’s Law Joseph Louis Gay-Lussac 1778-1850 Held volume constant Temp = pressure Temp = pressure Direct Relationship

Gay-Lussac’s Law

If a gas at a temp of 30 C and a pressure of 2 atm is Gay-Lussac Problem If a gas at a temp of 30 C and a pressure of 2 atm is raised to 500 K, what is the new pressure? P1 = P2 T1 T2 *temp must be in Kelvin *Be careful…notice one temperature is in Celsius and the other is in Kelvin. Just change the Celsius temperature to Kelvin 2 atm = x atm 303 K 500 K X = 3.30 atm

It is extremely difficult to hold any of these variables COMBINED GAS LAW (Table T) It is extremely difficult to hold any of these variables (temperature, pressure or volume) constant. Usually, all three change. If all three change, use the combined gas law. V1P1 = V2P2 T1 T2

Combined Gas Law Problem If 100 mL of a gas at STP is raised to a temperature of 500 C and a pressure of 300 kPa, what will be the new volume? *STP give you the conditions for temperature and pressure. You must use Table A if you don’t remember! V1P1 = V2P2 T1 T2 (100 mL)(101.3kPa) = (x mL)(300 kPa) 273 K 773 K X = 95.61 mL

Avogadro’s Hypothesis Equal volumes of gases at the same temperature and pressure contain equal number of particles 3 liters of H2O (g) and 3 liters of Ne (g) have equal number of particles but their mass is very different from each other

Kinetic Molecular Theory (KMT) of an Ideal Gas The particles of a gas in constant, random, straight-line motion. Collisions are elastic-KE is transferred without loss from one particle to another. Total KE RTS. 3. There is a great distance between gas molecules 4. There is no attraction between gas molecules 5. A gas has no volume.

Yet, a real gas does have attractive forces and does have a volume…so numbers 4 & 5 do not hold for a real gas. The KMT is still sound so we still use it even though some aspects of it are incorrect. So…there is no ideal gas…it only exists in theory Under what conditions will a real gas behave most ideally? Low pressure and high temperature Remember: P L I G H T pressure low ideal gas high temperature

What type of gases behave most ideally? The lighter the gas, the more ideally it behaves. Therefore, H2 and He are the two gases that behave most Ideally. Question: Which of the following gases behaves most ideally? A. O2 32 g C. NH3 17 g 64 g D. SO2 B. CO2 44g Therefore it is NH3 because it is the lightest!

Physical Means of Separating Mixtures Filtering-a process in which an insoluble solid is recovered from a mixture The solid remains on the filter paper and anything dissolved in the water, passes through the filter paper. Ex. Sand, salt and water. Sand would remain on filter paper because it does not dissolve in water but the filtrate would have water and dissolved salt in it. To recover the salt, evaporate the water and the salt will remain.

Chromotagraphy- is an analytical technique for separating and identifying mixtures that are or can be colored, especially pigments

Separation of a mixture based on differences in boiling points Fractional Distillation/Distillation- A process used to separate dissolved solids from a liquid, which is boiled to produce a vapor that is then condensed into a liquid Separation of a mixture based on differences in boiling points