Chapter 3: Matter and Energy

Pure Substances and Mixtures

a fixed and definite composition

Contain two or more different substances that are physically combined

• Can be physically separated

Elements → 1 type of atom (periodic table)

Compounds → 2 or more chemically combined atoms that are always in the same ratio (Water = H₂0)

Homogeneous → Uniform composition/ appears the same like milk (although it’s made up of many things)

Heterogeneous → Mixed composition/ appears different like spoiled milk (things are visibly all over)

Solid, liquid, and gas

Shape: Definite

Volume: Definite

Particle arrangement: Close; Fixed

Particle interaction: Very strong

Particle movement: Vibrate; Very slow

Shape: Indefinite (takes the shape of its container)

Volume: Definite

Particle arrangement: Close; Mobile

Particle interaction: Strong

Particle movement: Moderate

Shape: Indefinite (takes the shape of its container)

Volume: Indefinite (takes the volume of its container)

Particle arrangement: Random; Far apart

Particle interaction: Essentially none

Particle movement: Very fast

Heat

Characteristics observed or measured without changing the composition of a substance

• Shape, physical state, boiling/freezing point, density, color

Occurs in a substance if there is

• State change

• Change in physical shape

• No change in identity and composition of the substance

Describe the ability of a substance to become one or multiple different substances

A new substance forms that has new chemical and physical properties

Measure of how fast particles move

• How hot or cold an object is compared to another object

Kinetic energy

Fahrenheit → U.S Unit

Celsius → Metric Unit

Kelvin → SI Unit

Fahrenheit: 32°

Celsius: 0°

Kelvin: 273 K

Fahrenheit: 212°

Celsius: 100°

Kelvin: 373 K

F = 1.8(C) + 32

K = C + 273

It is the absolute temperature scale

• No degree sign

• No negatives

• Starts at 0K which the absolute lowest temperature can possibly be

The ability to do work

• Makes objects move

Kinetic and Potential

Energy of motion

• Swimming, water running down a dam, working out

Stored energy for use at a later time

• Gasoline, coal, food, chemical bonds, compressed spring, water at the top of a closed dam

By the position of the object and/or the chemical composition of a substance

The faster particles move the greater the thermal energy(temperature) of the substance

Energy transferred from hot to cold particles

The molecules increase motion and eventually have enough energy to change states

Solid → Liquid

SI Unit: Joule(J) or Kilojoules (kJ)

Metric Unit: Calories (cal) or Kilocalories (kcal)

• The amount of energy needed to raise the temp of water by 1°C

4.184J = 1 cal

• Exact; doesn’t not count toward sig figs

Nourishment or energy obtained from food

Nutritionists burn food in it

• Measures heat transfer

• The heat released from burning a food sample is used to determine the energy value for that food

1 Cal = 1000 cal

OR basically, 1 Cal = 1 kcal

The amount of heat that raises the temperature of 1g of a substance by exactly 1°C

• Different for each substance

• The ability of a substance to retain heat

SI Unit: J/g°C

Metric Unit: cal/g°C

heat/(grams x ∆T) = cal(or J)/g°C

1.00 cal/g°C OR 4.184 J/g°C

b - the water’s heat is released, warming the air

a - the sand does not retain heat very well

mass x ∆T x specific heat = cal/J

(specific heat must also match the energy unit)

S → L = Melting; absorbs heat

L → S = Freezing; releases heat

L → G = Evaporation/Vaporization; absorbs heat

G → L = Condensation; releases heat

S → G = Sublimation; absorbs heat

G → S = Deposition; releases heat

Releases heat

Takes in heat

Sublimation

Amount of heat released when 1g of a liquid freezes at its freezing point

AND

Amount of heat needed to melt 1g of a solid at its melting point

Heat released during freezing = Heat needed to melt (for any given substance)

w/o changing temperature

Surface molecules gain sufficient energy to become gas

Gas looses energy; becomes liquid

All molecules gain enough energy to form a gas (vaporize)

• Bubbles of water vapor appear throughout the liquid

Amount of heat to change 1g of liquid to gas at its boiling point

AND

Amount of heat released when 1g of gas changed to liquid at its boiling point

w/o changing temperature

Surface particles of solid become has directly gas

• No temperature change

Dry ice goes through sublimation at 78°C

Gas particles to solids

• Doesn’t pass through the liquid stage

True; the absorbed heat is used to break the forces of attraction between particles, not to heat the substance

Carbohydrates: 4 calories per gram

Proteins: 4 calories per gram

Alcohol: 7 calories per gram

Fats: 9 calories per gram