Chemistry of baking

Pure substances

Made out of an element or compound. Substance has exact properties.

Element

a pure substance that consists entirely of one type of atom

Compound

pure substance that formed when 2 or more elements combine together in fixed whole number ratios and cannot be broken down with physical means

Mixture

A physical combination of pure substances

Homogenous mixture

All components of mixutres are in the same phase (solid, liquid, etc), and uniform composition

Heterogeneous mixture

Non-uniform composition (seperating line/phase boundary), some components in different phases

Emulsion

System consisting of two immiscible liquids, one of which is dispersed in the other in

the form of small droplets

fractional distillation

a mixture of liquids is separated into its components by successive vaporizations and condensations in a vertical fractionating column. Used for close boiling points

Simple distillation

Heating the mixture to vaporize the most volatile component. Used for significant differences in the boiling points.

Seperation funnel

Used to separate immiscible liquids solvents based on their different phases

immiscible liquids

substances that do not mix or dissolve into each other forming distinct layers

gel electrophoresis

Gel electrophoresis works by separating molecules based on size and charge. Molecules move through a gel matrix toward an electrode, with smaller or more strongly charged molecules moving faster, causing them to separate.

Solid

Particles are tightly packed and vibrate in place, giving a fixed shape and volume.

liquid

Particles are close but can move past each other, giving a fixed volume but no fixed shape

Gas

Gas is a state of matter in which particles are widely spaced, move freely, and have no fixed shape or volume.

Vaporization

Process where a liquid turns into a gas when particles gain enough energy to overcome intermolecular forces.

Evaporation

Particles at the surface of liquid gain enough energy to overcome intermolecular forces, slow rate of reaction and at below boiling point.

Boiling

Particles throughout the liquid gain enough energy to overcome intermolecular forces at a set boiling point and much faster rate of reaction. Endothermic process.

Condensation

Gas to liquid (exothermic)

sublimation

solid to gas (endothermic)

deposition

gas to liquid (exothermic)

Energy during phase change

No change in average kinetic energy as energy transferred is used in order to break or form bonds creating a change in potential energy

empirical formula

smallest whole number ratio of atoms of each element in a compound

Hess's Law

If a substance or substances (A) is converted to another substance or substances (B) in a single step or in multiple steps (C, D, etc), the total energy change is the same regardless of the route.

Thermal decomposition

The breaking up of a chemical substance through heat (endothermic)

Neutralisation reaction

The reaction of an acid and a base forming a salt (containing the anion of the acid and the cation of the base) (exothermic)

Single displacement reactions

Where the more reactive element is able to replace, displace or replace the less reactive element from its compound AB+C→AC+B

Double displacement reactions

AB+CD→AD+CB

Combustion reaction

Fuel is ignited in the presence of oxygen creating H₂O, CO₂ and heat (exothermic)

Temperature

Average kinetic energy of particles

Heat

The transfer of thermal energy between systems or objects due to a temperature difference, flowing from hot to cold until thermal equilibrium is reached

Enthalpy change (∆H)

Change of energy that occurs in a chemical reaction (endothermic or exothermic)

saturated

When a solvent has dissolved the maxium amount of solute it cna dissolve meaning it cannot dissolve any mroe solute

precipitate

Insoluble solid forming through a reaction in a solution

solubility

How much solute can be dissolved in given solvent at a given temperature

Atom economy

A measure of the mass of starting materials that end up as useful products.

(mass of wanted products/ total mass of reactants) x 100= %

exothermic reaction

Heat is released to the surroundings, ∆H is negative, the energy is stored in the products is less than in the reactants, reactants is more stable than products. (Neutralization and combustion)

Endothermic reaction

Heat absorbs from the surroundings in the form of heat, ∆H is positive, energy in products is more than energy in reactants, products are less stable

factors that cause experimental yield to be lower than theoretical yield

Incomplete reactions: Some reactants may not fully react.

Loss of product during transfer or filtration: Some material can stick to equipment or be lost in handling.

Side reactions: Formation of unwanted by-products reduces the amount of desired product.

Purification losses: Crystallization, drying, or other purification steps may remove some product.

Volatile products: Some products may evaporate during the experiment.

factors that cause experimental yield to be higher than theoretical yield

1. impurities in product
2. product not fully 'dried'
3. incomplete reaction

crystal

solid material with a repeating pattern of particles, (H2O in hydrated compounds)

Setting up of a calibration curve

Minimum of 5 stock dilutions concentrations and distilled water as reference (zero the colorimeter on the distilled water). Measure the absorbance at set wavelength if using spectrophotomer.