Honors Chemistry Midterm Exam Review

Unit 1, 2, 3, 4.1, and 4.2

Mass

Number of particles

M= DxV

Volume

The space the particles take up

V= M/D

Law of Conservation of Mass

When a system changes macroscopically the mass will increase when a substance is added, decreases when the original substance is removed or stay the same if nothing + or -

Surrounding

Everything outside the system/the stuff that isn’t measured

System

Anything included in the measurement

Density

The spacing of particles

D=M/V

Chemical Change

A new substance is formed

• Can increase and decreases mass

Physical Change

The partical identity is the same

Slope

• Rise/Run

• For Every 1 ____________________.

  ex.) For Every 1 mL Corn Syrup has an additional 1.49g

Random Errors

Can affect measurements in both directions unpredictably

• ex.) Doing your math wrong

• Different students reading the measurements wrong

Systematic Errors

Affect all measurements in same direction

• Ex.) Using Inches instead of cm

• Measuring from the end of the ruler instead of zero

• Not tearing the graduated cylinder on the scale

Precision

Is consistent/the clumpiness of your data

Accuracy

Is correctness to the expected value

Vibrating

Motion of solid particles

Sliding

Motion of liquid particles

Bouncing

Motion of gas particles

Higher average energy/motion of particles

What happens in higher temperature?

Heating the lid caused the particles in the metal to move faster and mover farther apart. Thus, the lid became “larger” so it could be more easily removed from the jar.

A pickle jar lid is really hard to open, and a girl puts the pickles under hot water. The lid is now easy to open, why?

Thermal Expansion

An increase in a material's volume when temperature increases

• occurs in solids, liquids, and gases

Temperature

Degree of hotness

Heat

Quality of hotness

• Takes mass into consideration

Law

What happens/happened/will happen

Theory

How or why something happens/happened/will happen

• both equally weighted; theories never become law

Pressure

The force of particle collisions on a surface

Atmospheric pressure

Total force from collisions of atmosphere particles on a surface

• relationship between altitude and atmosphere pressures

• 76 mmHg, 101.3 kPa, 14.7 psi, 1 atm

Manometer

Used for determining internal pressure by comparing w/ known atmospheric pressure

• determine the difference, which is pushing harder?, Room ±/- difference = pressure

Barometer

Used to measure atmospheric pressure

• A tube is filled with mercury and the tube sits in a pool of mercury. The atmosphere pressure pushes down on the mercury and pushes the it up the tube. mm is used to measure.

Solid

• Space: Fixed

• Volume: Fixed

• Density: Highest (>1g/cm3)

• Compressibility: No

• Particle: Lowest

• Diffusion: No

Liquid

• Space: Variable

• Volume: Fixed

• Density: Middle (~1 g/mL)

• Compressibility: No

• Particle Motion : Middle

• Diffusion: Yes

Gas

• Space: Variable

• Volume: Variable

• Density: Lowest (1000x less dense)

• Compressibility: Yes

• Particle Motion : Highest

• Diffusion: Yes

1. Warmer air particles collide with glass particles of thermometer, transfer their energy, and glass particles begin moving faster

2. Warmer glass particles collide with alcohol particles inside thermometer, transfer their energy, and alcohol particles begin moving faster

3. Alcohol particles collide more energetically and spread out

   
   

Explain why the level in a thermometer rises when placed in warm fluid

Kelvin is superior because 0 Kelvin is 0 particle motion while 0 Celsius is the freezing point of water not particle motion.

Why is the Kelvin scale superior than Celsius for describing the behavior of particles?

Increases

As temperature increases, volume ______________

Increases

As temperature increases, pressure ______________

Decreases

As volume increases, pressure ________

Increases

As number of particles increases, pressure ___________

Diffusion

random particle collions

Melting

Solid —> Liquid

Evaporation

Liquid —> Gas

Sublimation

Solid —> Gas

Condensation

Gas —> Liquid

Freezing

Liquid —> Solid

Deposition

Gas —> Solid

Vaccum

Means there are no particles (or a small number of particles so small that its negligible)

Energy

Can be stored and transferred into/out of different '“accounts” but is not itself changed. It causes changes in systems

1. Eth / Thermal Energy (Kinetic)

Energy associated with particle motion

Diagonal part on the cooling/heating curve

2. Eph / Phase Energy (Pontential)

Energy associated with particle spacing

Flat part on the cooling/heating curve

3. Ech / Chemical Energy

Energy associated with Chemical bonds

The 3 types of Energy “accounts

Calorimetry

Metal —> Water (Energy out —> Energy In)

• - Q = Q

• M*C*T = M*C*T

Calorimeter

• Can be used to measure the heat capacity of a specific object

• The quantity of heat released by an object is equal to the quantity of heat absorbed by the water

Pure Substance

All one type of particle

Element

Any substances on the periodic table

• All elements are pure substances, but not all pure substance are an element

Mixture

More than 1 particle in the same space but still separate from one another

• Can be physically separated

• Components retain original properties

Compound (Molecule)

More than 1 element type bounded together

• Has different properties than components

• Cannot be physically seperated

Hoffman Apparatus

• When we turn on the electricity bubbles form on each side. One of it is Hydrogen the other is oxygen

• It is breaking the bonds of water

• Hydrogen is positively charged so it is attracted to the negative electricity

• Oxygen is negatively charged so it is attracted to the positive

Mass - # of particles
Volume - total space occupied by particles
Density - spacing between particles
Specific heat capacity - energy required to raise 1g of a substance by 1°C
Boiling point - temperature at which liquid turns to gas
Melting point - temperature at which solid turns to liquid

Identify the properties of matter we've investigated so far and define them

Will not change - mass, specific heat capacity, melting and boiling points
Could change - volume, density

What will not change in a closed system? What could change in a closed system?

Temperature

Hotter temperature = faster particles
Colder temperature = slower particles

The warmer particles from the hot chocolate collide with the cooler particles in the air and transfer their energy. The less "hot" hot chocolate particles get slower and closer together.

Describe what happens (at the particle level) when a glass of hot chocolate cools down to room temperature

Magnet - iron and sulfur - magnetism
Dissolve and filter - sand and salt - particle size
Chromatography - black ink - solubility (how easy something dissolves)
Centrifuge - blood - density (that spinning device like a washing machine)
Distillation - rubbing alcohol - boiling point

Describe the various ways in which a mixture could be physically separated, and the physical property being used to perform the separation

This is a chemical separation, chemical bonds were broken. The others were just mixtures that can be physically separated

Describe how the separation of hydrogen from oxygen in water is different than the previous examples of separation

5% Rule

(Y-intercept/Highest measured Y value) * 100

The percentage should be between 5% and -5%

Q - heat capacity (energy J)
M - mass of substance
C - identity (J/g°C)
∆T - change in temperature
Hv - heat of vaporization
Hf - heat of fusion

Energy transfers variables

Sigfig rules

1) All non zeros are significant
2) If a 0 is between 2 non zeros, it is significant
3) a 0 is insignificant if it is at the end of a number and there is no decimal present
4) The first zeros are not significant (Everything to the left is not significant)
5) everything in front of notation is significant (scientific notation)

Electrolysis

A process by which an electric current breaks chemical bonds.