Combustion - Part 1

Question 1

What is matter?

Answer 1

Everything that takes up mass or space.

Can be solids, liquids, or gases.

Question 2

What is a physical property?

Answer 2

It’s a characteristic of a substance that can be observed without changing the identity of the substance.

Examples : color, oder, texture, state of matter, mass, weight, density magnetism, ,and melting and boiling point.
-Transparency - degree to which light can pass through a substance.
-Mallebility - ability to be reshaped by the application of physical force
-Conductivity - ability to transmit heat or electricity

Question 3

What is a chemical property?

Answer 3

It’s a characteristic of a substance that is observable only when the substance interacts with another substance

It creates a new substance.

It includes flammability (ability to burn) or reactivity (ability to interact with other substances to produce new substances).

Question 4

What is an intensive property?

Answer 4

It’s a physical property that depends only on a substance’s identity and not on the amount of sample present.

Includes melting & boiling point, density, conductivity, and magnetism.

Question 5

What is an extensive property?

Answer 5

It’s a property that depends on the amount of sample present.

Includes mass, volume, and length.

Question 6

What is a physical change?

Answer 6

It’s a change in some of the physical properties of matter but not it’s identity.

Examples : Melting, boiling, cutting, & bending

Question 7

What is a chemical change?

Answer 7

It’s a change in the identity and properties of matter.

Examples : Burning, cooking, reacting with water, & reacting with air.

Indicators of a chemical change : color change, solid disappearance, gas formation, light and heat production, and percipitate formation (solid that forms from a liquid during a change process).

Question 8

What is kinetic-molecular theory?

Answer 8

It’s a theory that describes gases as a large number of constantly and randomly moving particles that collide with each other and with the walls of the container.

-Made of large number of hard spheres that are in continuous, random motion
-Most of the volume is empty space - very small volume relative to the spaces between them.
-there is no force of attraction or repulsion between gas particles (a limitation)
-Collisions are perfectly elastic
-Average kinetic energy depends only on temperature
- Is compressible (volume change with increased pressure), forces particles close together
- Volume and shape expand to fill container
- large spaces between gas particles from lack of interaction

Question 9

What is an example of an inverse relationship?

Answer 9

Pressure and volume are inverse relationships.

When temperature is constant.
Smaller volume - crowded particles - more collisions - higher pressure
Collisions with container walls - pressure, more or harde collisions - greater pressure, p=F/A
Average kinetic energy of particles - temperature, fater motion - higher temperature

Question 10

What are some direct relationships?

Answer 10

• volume and moles
  1. more gas particles - more volume
• pressure and temperature
  1. higher temperature - more kinetic energy - more collisions - higher pressure
• volume and temperature
  1. higher temperature - more kinetic energy - more space between particles - higher volume
• pressure and number of moles
  1. more gas particles - more collisions - higher pressure

When one increases the other will too. When one decreases the other will too.

Question 11

What is diffusions?

Answer 11

The spread of particles through random motion from regions of high concentration.

Net diffusion ends when concentrations are equal

Question 12

What is effusion?

Answer 12

The movement of a gas through a small opening into a larger volume.

Question 13

Kinetic energy for liquids

Answer 13

• Comparable with intermolecular attractions - denser than gases - not compressible - Volume does not change
• Able to flow - take shape of container
• Liquids are int eh middle of gases and solids

Are used for hydraulics (transmit force) since they aren’s compressible. Car brakes, airplane flaps, construction equipment, and robotics are just a few examples.

Question 14

Intermolecular forces and condensation

Answer 14

• Affect interactions between particles
• Stronger forces - more energy to oversom
• Condensation : kinetic energy < intermolecular forces
• Evaporation/boiling : kinatic energy > intermolecular forces

Question 15

Intermolecular forces and freezing

Answer 15

• Liquid particles : constant, random motion
• Solid particles : fixed in place, vibrate
• Freezing : kinetic energy < intermolecular forces
• Melting : Kinetic energy > intermolecular forces

Question 16

What is viscosity?

Answer 16

It’s the thickness or resistance to flow of a liquid

Depends on temperature, directly correlated to to size (mass) of particles, and directly correlated to strength of intermolecular forces.

Question 17

What is surface tension?

Answer 17

It’s the tendency for a liquid surface to resist penetration

Directly correlated to intermolecular attraction, surfactant (for example dish soap and water) can reduce surface tension.

Question 18

Dissolving

Answer 18

Liquids can dissolve other liquids, solids, and gases. That is when they become integrated into a host liquid (solvent).

Particles dispersed evenly. Missible liquids - dissolve each other. Immiscible liquids - particles remain seperate.

Question 19

What are solids?

Answer 19

They’re a low energy state of condensed matter characterized bu structural rigidity and resistance to changes in shape of volume. High density & made of neutral particles or cation - anion pairs.

Temperature decreases - kinetic energy decreases - and particle motion slows
Freezing : kinetic energy < intermolecular forces

Question 20

What are chrystalline solids?

Answer 20

They’re solid characterized by an orderly periodic lattice of component particles.
* Ordered
* Long-range order : an arrangement of particles in which the particles are ordered over many multiple of the average particle diameter

Lattice : regular arrangement of atome, ions, or molecules
Unit cell reapeated to form crystal, incompressible - dense and hard, particles vibrate

Question 21

What is an amorphous solid?

Answer 21

It’s a solid matter with particles that are arranged in a ununiformed pattern.
* Rapid cooling - not complete assembly of unit cells
* Long-range absent - particles ordered over many multiples of average particle diameter

Question 22

What is a plasma?

Answer 22

It’s a high energy state of matter characterized by ionized particles
* Temperature may be thousands of degrees
* conducts electricity
* is compressible
* has no definate shape or volume
* low density

In nature - electrons almost 20,000 degrees Celsius - lightning, Stars, Auroras
Human-made - fluorescent lights, Ion thrusters, Arc welders, Plasma displays, plasma balls

Question 23

What is thermal equilibrium?

Answer 23

It’s a temperature equal to the surroundings and plasmas can get cold when:
* light electrons move fast (hot)
* heavy nuclei ar slow (cold)
* electron kinetic energy is converted to light
* fewer than 1% of particles are ionized
* They are non-thermal plasmas

Question 24

Equilibrium between liquid and gas

Answer 24

Particles move between liquid and gas phase, gas particles exert pressure
Vapor pressure : the pressure exerted by the gas in equilibrium with a pure liquid at a given temperature. Realted directly to temperature
The higher the vapor pressure, the more readily the liquid evaporates

Question 25

The phase changes

Answer 25

• Melting - colid to liquid
• Boiling - liquid to vapor
• Sublimation - solid to gas
• Freezing - liquid to solid
• Condensing - vapor - liquid
• Deposition - vapor to solid

Substances increase (gain,absorb) for first three and substances decrease (release) for the last three.
Temperature is constant during phase change.