Molecules, Compounds, Matter, and Mass

Molecules and Compounds

• A molecule comprises two or more atoms linked by chemical bonds, usually covalent.
• Molecules form a stable entity and can be purified through physical processes like distillation, crystallization, sublimation, and chromatography.
• A compound involves the combination of two or more atoms from different elements.
• Examples of molecules include Oxygen (O2) and Iodine (I2).
• Examples of compounds include Pt(NH3)2Cl2, EtOH (Ethanol), and Water (H2O).

Matter and Mass

• Matter is anything that occupies space and has mass.
• Mass measures the quantity of matter.
• The SI unit for mass is the kilogram (kg).
• 1 kg equals 1000 g, or 1 x 10^3 g.

Weight

• Weight refers to the force exerted by gravity on an object.
• As a force, weight is measured in force units (1N = 1 kg m/s²).
• Weight and mass units have a shared history, partly due to the difference between them not initially being well understood.
• The relative weight equation is weight(rel) = c x mass.
• On Earth, c equals 1.0, while on the Moon, c is approximately 0.1.
• An object with a mass of 1 kg on Earth would weigh 0.1 kg on the Moon.

SI Base Units

• Length's SI unit is the meter represented by the symbol m.
• Mass's SI unit is the kilogram represented by the symbol kg.
• Time's SI unit is the second represented by the symbol s.
• Electric current's SI unit is the ampere represented by the symbol A.
• Temperature's SI unit is the kelvin represented by the symbol K.
• Amount of substance's SI unit is the mole represented by the symbol mol.
• Luminous intensity's SI unit is the candela represented by the symbol cd.

SI Prefixes

• Tera- (T) signifies 10^12.
• Giga- (G) signifies 10^9.
• Mega- (M) signifies 10^6.
• Kilo- (k) signifies 10^3.
• Deci- (d) signifies 10^-1.
• Centi- (c) signifies 10^-2.
• Milli- (m) signifies 10^-3.
• Micro- (μ) signifies 10^-6.
• Nano- (n) signifies 10^-9.
• Pico- (p) signifies 10^-12.

Volume

• Volume's derived SI unit is the cubic meter (m³).
• 1 cm³ equals (1 x 10^-2 m)³ which equals 1 x 10^-6 m³.
• 1 dm³ equals (1 x 10^-1 m)³ which equals 1 x 10^-3 m³.
• 1 L equals 1000 mL, which equals 1000 cm³, which equals 1 dm³.
• 1 mL is equivalent to 1 cm³.
• 1 m³ equals 1000 L, which equals 1 x 10^6 cm³.

Density

• Density's derived SI unit is kg/m³.
• 1 g/cm³ equals 1 g/mL, which equals 1000 kg/m³.
• Density is calculated as mass divided by volume, d = m/V.

Density Calculations

• The mass of a piece of platinum metal, given a density of 21.5 g/cm³ and a volume of 4.49 cm³, is calculated by m = d x V = 21.5 g/cm³ x 4.49 cm³ = 96.5 g.
• The density of mercury, the only liquid metal at room temperature, is 13.6 g/mL.
  • The mass of 5.50 mL of mercury is calculated: m = d x V = 13.6 g/mL x 5.50 mL = 74.8 g.
  • 74.8 g is equivalent to 0.0748 kg (74.8 g x (1 kg / 1000 g) = 0.0748 kg).

Density Exercise

• A metal has a mass of 600 g and a volume of 350 cm³.
  • To determine the density in g/mL, convert cm³ to mL: 350 cm³ x (1 mL / 1 cm³) = 350 mL.
  • Calculate the density: d = m/V = 600 g / 350 mL = 1.714 g/mL.
  • To find the density in kg/m³: 1.714 g/mL x (1 kg / 1000 g) x (1 mL / 1 cm³) x (1 cm³ / 1x10^-6 m³) = 1714 kg/m³.

Density Problem

• An object has a density of 1.59 g/mL and a mass of 0.058 kg.
• Convert mass to grams: 0.058 kg x (1000 g / 1 kg) = 58 g.
• Volume is determined: V = m/d = 58 g / 1.59 g/mL = 36.5 mL.
• Convert volume to cm³: 36.5 mL x (1 cm³ / 1 mL) = 36.5 cm³.

Temperature

• Temperature can be measured in Celsius (°C), Kelvin (K), and Fahrenheit (°F).
• Water's boiling point is 100°C, 373.15 K, and 212°F.
• Water's freezing point is 0°C, 273.15 K, and 32°F.
• Temperature conversions: (°F - 32) x 5/9 = °C, (°C x 9/5) + 32 = °F, and °C + 273.15 = K.

Temperature Conversion Example

• To convert 172.9 °F to Celsius:
  • Apply the formula: °C = 5/9 x (°F - 32).
  • °C = 5/9 x (172.9 - 32) = 78.3°C.

Melting Point of Mercury Example

• Mercury melts at 234 K.
• Convert to °C: °C = K - 273.15 = 234 - 273.15 = -39.15 °C.
• Then, convert to °F: °F = (°C x 9/5) + 32 = (-39.15 x 9/5) + 32 = -38.47 °F.

Temperature Conversion Exercise pt. 2

• Convert 79 °C to K: K = °C + 273.15 = 79 + 273.15 = 352.15 K.
• Convert 79 °C to °F: °F = (°C x 9/5) + 32 = (79 x 9/5) + 32 = 174.2 °F.

Energy and Work

• Energy is a body's capacity to move itself or another object.
• Work is defined as the movement energy creates.
• Energy is the capacity to do work.
• Work (W) is the energy it takes to move an object.
• Work = Force x Distance
• Joules = Newtons x meters
• J = N x m

Units of Energy

• Joule or Julio (J) is the international system unit.
• Vatio-hora (Wh) is a unit to express the consumption of energy.
• Caloría (Cal) is a unit used in the study of the energetic content of foods.
• Electronvoltio (eV) is a unit used for the study of the transmitted energy for very small elements.
• British Thermal Unit (BTU) is a unit that is utilized primarily in air conditioning.
• Tonelada equivalente de petróleo (Tep) demonstrates the energetic efficiency of a ton of petroleum.

Energy Content in Foods

• Caldo de pollo con verduras has 120 kcal per 100g serving.
• Canelloni has 123 kcal per 100g serving.
• Carne asada has 199 kcal per 100g serving.

Calories in Foods

• 1g carbohydrates provide 4 calories.
• 1g proteins provide 4 calories.
• 1g fats provide 9 calories.
• 1g alcohol provides 7 calories.

Energy Measurement in Joules

• The unit of measure of energy in the International System of Units is the joule (J).
• 1 Vatio-hora (Wh) is equivalent to 3600 J.
• 1 Caloría (Cal) is equivalent to 4.1868 J.
• 1 Electronvoltio (eV) is equivalent to 1.602176634·10^-19 J.
• 1 British Thermal Unit (BTU) is equivalent to 1055.05585 J.
• 1 Tonelada equivalente de petróleo (Tep) is equivalent to 41868000000 J.

Energy Calculation Example

• To calculate the number of Joules in 551 grams of carne asada:
  • Given 100 g carne asada = 199 Kcal and 1 Cal = 4.1868 J.
  • Calculation: 551 g car asad x (199 Kcal / 100 g car asad) x (1000 cal / 1 Kcal) x (4.1868 J / 1 cal) = 4590784 Joules.
• To calculate how much canelloni a person needs to eat to obtain 3 x 10^6 Joules, given 100 g canelloni = 123 Kcal:
  • Calculation: 3 x 10^6 Joules x (1 Cal / 4.1868 Joules) x (1 Kcal / 1000 Cal) x (100 g Canelloni / 123 Kcal) = 583 g Canelloni.