TEAS 7 Chemistry: Physical Properties, States of Matter, and Water

Kinetic Molecular Theory

Theory that all matter is composed of particles (atoms and molecules) moving constantly in random directions.

Molecule motion changes as is heat added or removed.

What does the phase of a substance depend on?

1. Temperature

2. Pressure

Mass

Amount of matter in an object, the number of molecules

Volume

Amount of space occupied by a specific number of molecules

3 states of matter

1. Solid

2. Liquid

3. Gas

Solid

1. Fixed shape and volume

2. High pressure

3. Low temperature

4. High atomic attraction

Liquid

1. Fixed volume but changing shape (takes shape of container)

2. High pressure

3. Higher temperature

4. Weaker physical bonding

Gas

1. Changing volume and shape

2. Low pressure

3. Higher temperature

4. Weaker atomic attraction

Phase change

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

Involves adding or removing heat.

Exothermic reaction

A reaction that releases energy in the form of heat

Endothermic reaction

A reaction that absorbs energy in the form of heat

2 external factors that affect matter state

1. Temperature

2. Pressure

Vaporization

Liquid --> Gas

Spontaneous phase change

Adding heat = endothermic reaction

Evaporation

Liquid --> Gas

Phase transition

Adding heat

Happens at boiling point and depends on atmospheric pressure

Condensation

Gas --> Liquid

Phase change

Removing heat = exothermic reaction

Freezing

Liquid --> solid

Phase change

Removing heat = exothermic reaction

Sublimation

Solid --> gas

Skips over liquid phase

Phase change

Adding heat = endothermic

Sublimation = solid skips phase.

Deposition

Gas --> solid

Phase change

Removing heat = exothermic reaction

Physical properties of matter

Characteristics of matter that can be observed without changing the substance into something else: color, shape, hardness, mass, volume, density

Most important for the TEAS

Extensive physical properties

Properties that do depend on the amount of matter present

1. Mass

2. Volume

3. Heat Capacity

Intensive physical properties

Properties that do not depend on the amount of matter present

1. Boiling Point

2. Melting Point

3. Density

4. Molarity

Chemical properties of matter

Characteristics of matter that can be observed when a substance interacts with another substance to change composition and identity.

How a substance can change or not change based on interaction like burning and rusting

Melting

Solid --> Liquid

Phase change

Heat added = endothermic

Melting point

The temperature at which a solid becomes a liquid

Boiling point

The temperature at which a liquid changes to a gas (vapor).

The boiling point of water at sea level is 100°C (212°F).

Depends on pressure.

Molecular motion

The motion of atoms in an object

Affected by the temperature

Gasses have the most amount of molecular motion; solids have the least amount of molecular motion.

Molecular motion increases as heat is added.

Crystalline Solid

A solid that is made up of crystals in which particles are arranged in a regular, repeating pattern

Density

Mass/volume

"Mass divided by volume"

How compact a substance is

Memorize this formula for the TEAS. You might need to calculate the density in a question.

Triple Point

The temperature and pressure conditions at which the solid, liquid, and gaseous phases of a substance coexist at equilibrium

Critical Point

The point on a phase diagram at which the liquid and gas phases of a substance have the same density, and are therefore indistinguishable.

Dependent on temperature and pressure for gas and liquid states of a substance to coexist.

List the important general properties of water for the TEAS.

1. Water is tasteless, odorless, and colorless/transparent.

2. Water can dissolve almost any solid, liquid, or gas, earning it the term universal solvent.

3. Water's polar bonds create high surface tension and cohesion.

List the important chemical properties of water.

1. Water has polar covalent bonds (oxygen has negative charge; hydrogen has positive charge).

2. Water has a neutral pH of 7.

3. Water has a high specific heat capacity and high heat of vaporization.

4. Water has a maximum density at 4 degrees Celsius, which is about 39 degrees Fahrenheit.

5. Water's triple point is near absolute zero (273.1 degrees K), where it exists as a solid, liquid, and a gas all at once.

Why is water's high specific heat capacity important?

Water changes temperature more slowly than the environment.

Large amounts of heat can absorbed with little change to water's temperature.

Specific Heat Capacity

Amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius

Does water's boiling point change?

Yes. Water's boiling point changes based on altitude.

Why does ice float?

Ice is less dense than liquid water.

As water freezes, it expands, which increases its volume, so density decreases.

(Water's maximum density is about about 39 degrees Fahrenheit.)

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration

Passive transport

Osmosis

Diffusion of water through a selectively permeable membrane

Passive transport

Cohesion of water molecules

Water's hydrogen bonds creates surface tension and help water travel through capillaries without any use of energy.

Is energy required to move a substance from an area of low concentration to an area of high concentration?

Yes, energy is required (active transport). Energy is not required to move form areas of high concentration to low concentration.

How are osmosis and diffusion different?

Osmosis = only water

Osmosis moves the solvent through a selectively permeable membrane.

Diffusion = movement of any molecules down a concentration gradient.

Diffusion is the movement of solutes and does not require a membrane.

List 3 endothermic phase changes.

1. Melting

2. Vaporization

3. Sublimation

(Note: evaporation is technically a phase transition)

Cohesion

Attraction between molecules of the same substance

Adhesion

An attraction between molecules of different substances

Why does water have a high specific heat?

Water is joined with hydrogen bonds, which requires large amount of energy to break.

Water's capillary action and surface tension are the result of what property?

Cohesion

Water molecules have high polarity and stick together.

Solution

A homogeneous mixture of two or more substances

Involves solute dissolving in solvent

Solute + Solvent = Solution

Is formation of a solution a chemical or physical process?

Physical

Solute

A substance that is dissolved in a solution.

Solvent

A liquid substance capable of dissolving other substances

Water is the universal solvent

Water's ability to be a universal solvent is the result of which property?

Adhesion. Water is polar, which means it sticks to other, non-water, molecules.

Saturated Solution

Solution with the maximum amount of dissolved solute

Supersaturated Solution

Contains more dissolved solute than a saturated solution at the same temperature. Requires higher temperatures.

Dilution

Process of adding solvent to lower the concentration of solute in a solution

Solution Concentration

Amount of solute in a given amount of solvent

What are some ways to measure solution concentration?

1. Molarity

2. Parts Per Million (ppm)

3. Parts Per Billion (ppb)

4. Mole Fraction

When measuring solution concentration, what is unique about molarity?

It depends on temperature. Parts Per measurements aren't affected by temperature.

Hydrophilic solute

Dissolves in water

Polar

Hydrophobic solute

Does not dissolve in water

Fat soluble

Non polar

What increases the solubility of a gas?

Decreasing temperature

What increases the solubility of a solid?

Increasing temperature

(Think of how sugar crystals dissolve more easily in hot water)

What increases the solubility of a liquid?

Increasing temperature

Passive Transport

Moving molecules down a concentration gradient (high --> low) without energy

Examples: diffusion, osmosis

Active Transport

Moving molecules against the concentration gradient (low --> high) with energy.

A solution is undersaturated. What does this mean about its ability to dissolve solutes?

This solution can dissolve more solute until it reaches saturation.