Understanding Phase Changes in Physics: Key Concepts Explained
Quan una substància passa d’un estat a un altre, en física es diu que canvia d’estat.
SOLID -> (fusió) LIQUID -> (vaporització) GASOS
<- (solidificació) <- (condensació o gel)
Sublimació ————– ——————>
Crystallització ——-
Lleis de la solidificació:
a) Una substància és pura quan es fon, ho fa a una temperatura anomenada temperatura de fusió.
b) La temperatura de fusió es manté constant mentre la substància es solidifica.
c) Els líquids purs
Fundamental Building Blocks of Life: Elements and Molecules
Components of Living Matter
Composition of Matter
Matter consists of atoms.
Key Definitions
- An atom is formed by small particles.
- Elements are substances that consist of a single type of atom. There are 92 naturally occurring elements.
- Substances are mostly chemical compounds.
Chemical Components: Sources and Examples
Chemical components are unions of different atoms. They originate from:
- Rocks and minerals (inorganic world): For example, marble is calcium carbonate, and gypsum is calcium sulfate. Calcium
Essential Chemistry Concepts & Organic Reactions
Fundamental Chemistry Definitions
Analytical Chemistry & Solutions
- Titration
- A technique to determine the concentration of a solution by reacting it with a solution of known concentration.
- End Point
- The point in a titration at which the indicator changes color, signaling that the reaction is complete.
- Equivalence Point
- The exact point at which the amount of titrant is chemically equivalent to the substance being titrated.
- Titration Error
- The difference between the end point and the equivalence point.
Understanding Acids and Bases: Theories, Strength, and Dissociation
Arrhenius Theory of Acids and Bases
An electrolyte is a substance that, in aqueous solution, conducts electricity. Svante Arrhenius established that when an electrolyte dissolves in water, it dissociates into two electrically charged ions with opposite charges (positive: cation, negative: anion). This theory is valid for any substance that conducts electricity in aqueous solution. Since acids and bases conduct electricity, these ideas were applied to them. An acid is any substance that dissociates
Read MoreUnderstanding Matter: Properties, Scientific Method, and Gas Laws
Properties of Matter
General Properties
These are values that serve to identify a substance, such as temperature, mass, and volume.
Characteristic Properties
These are unique and specific values for each substance, including density, melting point, boiling point, hardness, water solubility, and electrical conductivity.
Density
The amount of mass per unit volume (e.g., lead is dense, cork is less dense).
Hardness
The resistance a substance has to scratching or abrasion (e.g., diamond is very hard, talc is
Chemical Titration Methods: Complexometric & Precipitation Analysis
Complexometric Titrations
Complexometric titrations are a type of volumetric analysis involving titrants that form a soluble complex with the analyte (the substance being valued). In any complex, two main parts are distinguished: the central atom (usually a metal atom or ion) and the ligand.
Types of Ligands in Complexometric Titrations
Atomic or Molecular Ligands
When the ligand is an atom or molecule, the resulting complex is often referred to as a coordination compound. For neutral ligands, the overall