grade 10 integrated Science:Chemistry topic:1 Phase changes, topic 2states of matter/kmt gases

phase

any part of a sample with uniform composition and properties(solid, liquid, gas)

Condensation

Gas to liquid

vapor

describes the gaseous state of a substance that is generally a liquid or solid at room temperature

Equilibrium

A state of balance

closed system

A system in which no matter is allowed to enter or leave

Equilibrium in a closed system

The rate of forward reaction is equal to the rate of the reverse reaction, No change is seen

vapor pressure

a measure of the force exerted by a gas above a liquid

mercury manometer

A blood pressure measurement device that uses a calibrated column of mercury to indicate blood pressure values.

volatile liquids

a liquid that evaporates readily or at a low temperature

non-volatile liquids

liquids that evaporate slowly

law of conservation of energy

Energy cannot be created or destroyed

condensation reaction

a chemical reaction in which two or more molecules combine to produce water or another simple molecule

Vaporization

The change of state from a liquid to a gas

boiling point

The temperature at which a liquid changes to a gas

Endothermic

Absorbs heat

Exothermic

Releases heat

heat of vaporization

The amount of energy required for the liquid at its boiling point to become a gas

formula for heat of vaporization

q=mHv

freezing point

The temperature at which a liquid changes into a solid

melting point

the temperature at which a substance changes from a solid to a liquid

heat of fusion

Amount of energy required to change a substance from the solid phase to the liquid phase.

Sublimation

A change directly from the solid to the gaseous state without becoming liquid

Deposition

Process in which sediment is laid down in new locations.

heating curve

a plot of temperature versus time for a substance where energy is added at a constant rate

cooling curve

a diagram that illustrates temperature changes and changes of state for a substance as heat is removed

phase diagram

a graph showing the conditions at which a substance exists as a solid, liquid, or vapor

triple point on phase diagram

all 3 phases can coexist simultaneously

Critical point on phase diagram

represents the temperature and pressure above which a supercritical fluid exists

critical temperature

the temperature above which a substance cannot exist in the liquid state

critical pressure

the lowest pressure at which a substance can exist as a liquid at the critical temperature

On a graph, where is the independent variable?

x-axis

Where is the dependent variable on a graph?

y-axis

intermolecular forces

forces of attraction between molecules

phase change

a change from one state (solid or liquid or gas) to another without a change in chemical composition

Evaporation

Liquid to gas

exothermic reaction

A reaction that releases energy in the form of heat

endothermic reaction

A reaction that ABSORBS energy in the form of heat

boiling

The temperature at which a liquid changes to a gas

Kinetic Molecular Theory (KMT)

a model that assumes that an ideal gas is composed of tiny particles (molecules) in constant motion

ideal gas

a hypothetical gas that perfectly fits all the assumptions of the kinetic-molecular theory

Real Gases vs. Ideal Gases

1) real gases deviate from ideal behavior at high pressures.

2) real gases deviate from ideal behavior at low temperatures

3) at a given P/T, stronger IMA's will result in greater deviation from ideal behavior

4) at high P/low T, the larger the size of the molecules results in a greater deviation from ideal behavior

Ideal Gas Law

PV=nRT

Real Gas Law

Decreasing the volume of a sample of gas makes it behave less ideally because the individual gas particles are in closer proximity in the smaller volume. They are more likely to engage in intermolecular interactions.

When do real gases behave like ideal gases?

high temperatures and low pressures

temperature

A measure of the average energy of motion of the particles of a substance.

kinetic energy

energy of motion

kinetic energy equation

KE=1/2mv^2

gas

A state of matter with no definite shape or volume

liquid

A state of matter that has no definite shape but has a definite volume.

solid

A form of matter that has a definite shape and volume

the 5 postulates of kinetic molecular theory?

1) KE (energy of motion) of a gas is directly proportional to Kelvin temperature --> the higher the temperature, the greater the kinetic energy of gas particles

KE = (1/2) mass x velocity^2

2) Gases consist of particles whose volume is negligible compared to volume of container, i.e., gas particles themselves effectively occupy zero space

3) gas particles are in continuous, random, and rapid motion

4) gas particles collide with each other and walls of container --> during these collisions, no energy is lost, i.e., they are elastic collisions

5) gas particles do not attract one another, i.e., effectively, each gas particle moves indepedently

gas pressure formula

P=F/A

Expansion of Gases

expand to fill container

fluidity

ability to flow

Density

the degree of compactness of a substance.

Compressibility of gases

because molecules in the gas phase are separated by large distances, gases can be compressed easily to occupy less volume

diffusion of gases

• Gases diffuse down pressure gradients

-High pressure -> low pressure

• In gas mixtures, gases diffuse down partial pressure gradients

High partial pressure -> low partial pressure

• A particular gas diffuses down its own partial pressure gradient

-Presence of other gases irrelevant

effusion

A process by which gas particles pass through a tiny opening

difference between diffusion and effusion

Diffusion: random molecular motion, causing a substance to move from an area of higher concentration to an area of lower concentration (diffusion down its concentration gradient).

Effusion: random molecular motion, causing a substance to escape a container through a very small openning

compressibility in gases

Gases can be compressed due to particle spacing.