Genetics, Thermodynamics, and Chemical Reactions Explained
Genetics and Heredity
Genotype: The complete set of genes an individual inherits from their parents.
Phenotype: The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.
Alleles and Inheritance
Homozygous: An individual possessing two identical alleles for a specific trait.
Heterozygous: An individual possessing two different alleles for a specific trait.
Gene: A unit of heredity containing genetic information, located on chromosomes in a linear sequence.
Alleles: Alternative forms of a gene.
Mendel’s Laws of Inheritance
- When crossing two purebred organisms with contrasting traits, all offspring will exhibit the dominant trait.
- Recessive traits, masked in the first generation (F1), reappear in the second generation (F2) in a 3:1 ratio (dominant:recessive).
- Each trait is inherited independently of other traits.
Autosomes: Non-sex chromosomes.
Heterochromosomes: Sex chromosomes.
Intermediate Inheritance: A pattern of inheritance where neither allele is completely dominant, resulting in a hybrid offspring with an intermediate phenotype.
Chromosome Theory of Inheritance
- Genes are located on chromosomes.
- Genes are arranged linearly on chromosomes.
- Recombination of genes on the same chromosome occurs through the exchange of chromosomal segments during crossover in meiosis.
Mutagenic Agents: Physical or chemical agents that cause alterations in hereditary material, such as X-rays causing chromosomal breakage.
Thermochemistry and Chemical Reactions
Enthalpy Variation: The heat absorbed or released when one mole of a compound is formed from its elements under standard conditions.
Thermochemical Equation: A balanced chemical equation that includes the physical states of reactants and products, along with the enthalpy change (ΔH). ΔH is positive for endothermic reactions and negative for exothermic reactions.
Heat of Combustion: The heat released when one mole of a substance is completely burned in oxygen. Combustion reactions are always exothermic.
Heat of Reaction: The heat absorbed or released during a chemical reaction. It is typically placed at the end of the reaction equation. The heat of reaction can be calculated using standard enthalpies of formation: ΔHreaction = ΣnΔHf(products) – ΣnΔHf(reactants), where n is the number of moles.
State Function: A property that depends only on the initial and final states of a system, not on the path taken. Internal energy is an example of a state function.
Measuring Heat of Reaction
To measure the heat of a reaction, you need a calorimeter, a thermometer, and a beaker. Measure the initial temperatures of the reactants separately, then mix them in the calorimeter and measure the final temperature of the mixture. The heat absorbed or released can be calculated using the formula: q = m * Csp * ΔT, where q is the heat, m is the mass, Csp is the specific heat capacity, and ΔT is the change in temperature.
Chemical Reactions at Constant Volume: Reactions performed in a closed container (calorimeter) where Qv = ΔU (change in internal energy).
Thermochemistry: The branch of chemistry that studies the relationship between heat and chemical reactions.
Thermodynamic Principles
First Law of Thermodynamics: It is impossible to create a machine that continuously produces work without consuming an equivalent amount of energy. Internal energy (U) represents the total energy of a system’s particles, including kinetic, potential, rotational, and vibrational energy. ΔU = Q – W, where Q is heat and W is work.
Laboratory Equipment
Volumetric Flask: A pear-shaped, flat-bottomed glass container with a long neck and a stopper. It has a calibration mark indicating the precise volume it holds at a specific temperature. Common capacities are 50, 100, 250, 500, and 1000 mL. Used for preparing solutions with accurate concentrations.
Erlenmeyer Flask: A conical flask with a flat bottom and a cylindrical neck. It often has graduation marks for approximate volume measurement. Primarily used for mixing and swirling liquids without spillage.