Notes, summaries, assignments, exams, and exercises for Chemistry for University

1. Sampling

Taking a tissue sample quickly and without traumatizing it.

2. Fixation

The sample is placed in fixatives, such as formalin, Zenker's solution, or Bouin's solution (the most commonly used). After fixation, the tissue changes color.

3. Dehydration and Clearing

First, remove excess fixative with water. Then, the tissue is dehydrated through a series of alcohol or acetone baths. The sample is immersed in increasing concentrations of alcohol: 50%, 70%, 96%, and finally 100% (absolute alcohol). This process typically takes 30 minutes.

After dehydration in alcohol, the sample is immersed in Methyl Benzoate I, where it initially floats and then sinks. Finally, it is submerged in Methyl Benzoate II. The clearing agent, Xylene, is then used for...

Error Variables in Micrometers

Error variables are errors that vary according to the dimension being measured. Such errors mainly come from variations in the passage of the screw micrometer. It is not possible to correct a variable error in the micrometer, but the error can be known if the tool has it.

Other Types of Micrometers

By suppressing, eliminating, or modifying the body of a standard micrometer, variants can be obtained. Different models are set up to fit a wide variety of measurements, including:

• Interior micrometer
• Micrometers with three inner supports
• Interior micrometers for small diameters
• Depth micrometers
• Special micrometers

The Melting Point

The melting point is a physical constant used in organic machines, but it can be defined as the...

Acid-Base Reactions

Acid-base reactions are essential in chemistry, allowing us to determine the concentration of an acid or base solution through titration. This process involves using a solution of known concentration (a standard solution) and an acid-base indicator.

Neutralization

Neutralization is the combination of hydrogen ions (H⁺) and hydroxide ions (OH^-) to form water (H₂O) and a salt. These reactions are exothermic, meaning they release heat.

Acid + Base → Salt + Water

Titration of a Strong Acid with a Strong Base

When titrating a strong acid (e.g., hydrochloric acid, HCl) with a strong base (e.g., sodium hydroxide, NaOH), the reaction is a straightforward neutralization:

HCl + NaOH → NaCl + H₂O

Titration of a Weak Acid with a Weak Base

Titrating...

Essential Chemistry Concepts

1. Thermochemistry

Thermochemistry is the branch of chemistry that studies the changes in temperature that occur during a chemical reaction.

2. Heat of Formation

Heat of formation is the energy inherent in elements, which is transformed when it receives energy from an external source.

3. Heat of Reaction

Heat of reaction is the energy absorbed or released during a chemical reaction.

4. First Law of Thermodynamics

The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only transformed.

5. What is a Solution?

A solution is a mixture of two or more components with a uniform consistency.

6. Types of Solutions

• Homogeneous
• Heterogeneous
• Simple Solution
• Colloid
• Suspension

7.

Biophysics II

Colloids

Colloids are suspensions of very small particles (micelles), even much larger than the dispersed molecules within a liquid. They are also called pseudo-solutions or colloidal solutions.

State of Sol and Gel

Protoplasmic colloids undergo sol-gel processing, also called reversal or phase change. Colloids present an intermediate state between solid, liquid, and gas. States in the protoplasm of sol and gel usually alternate due to changes in concentration. The most important sols in biology are protein dispersions in water.

Types of Colloids According to the Physical State of the Phases

The dispersant phase can be a solid, liquid, or gas, just as the dispersed phase may be liquid, solid, or gaseous. The passage from a sol to a...

Commercial Gypsum Composition and Purity

The commercial gypsum composition is formed by a mixture of Hemihydrate (HH) and some anhydrous Dihydrate (DH) nuclei, besides the impurities brought from the quarry.

Chemical Composition and Proportions

The typical proportions are:

• Hemihydrate (HH): 20% to 70%
• Anhydrite: 80% to 90%

Sources of Gypsum Impurities

Once obtained, it is necessary to distinguish two types of impurities:

Raw Material Impurities

These come from the source materials. If the gypsum stone contains impurities, these impurities will transfer to the final product.

Manufacturing Process Defects

These are impurities or defects produced during the manufacturing process, such as under-calcined (incocidos) and over-calcined (overcooked) material....

Aluminum

Aluminum is used in telescopes. Tempered powder paint is used in metal protection and the preparation of alloys. Aluminum forms alloys with other metals. Duralumin, an aluminum alloy, is used in aeronautics because it is very lightweight and has great resistance.

Aluminothermy

Aluminothermy is a metal extraction procedure that reduces metal oxides using aluminum powder. Metals such as chromium, manganese, and molybdenum are obtained using this method.

Salts of Aluminum

Important industrial salts are called alum (double salts).

Natural Aluminum

Aluminum is not found free in the Earth's crust. It is named after these characteristics:

1. Alumina
2. Hydroxide
3. Silicates

Obtaining Aluminum

Aluminum is extracted using the electrolytic method. Bauxite and cryolite...

Atomic Structure and Chemistry Fundamentals

Organic chemistry is the science of matter. All matter occupies space. Plasma is when atoms are in a high-temperature environment.

• Elements: A single type of atom that cannot be transformed into simpler substances.
• Compounds: Substances formed by different types of atoms combined in a constant ratio.
• Homogeneous: Has a single phase, and components are indistinguishable (H₂O + C₆H₁₂O₆). Can be separated by evaporation or distillation.
• Heterogeneous: Components can be distinguished from each other.
• Phase: A portion of matter with definite limits. Can be separated by filtering or decanting.

d = mass / volume

Prefixes: milli (m) - 10^-3 / micro (μ) - 10^-6 / nano (n) - 10^-9

1 kg = 1000 g and 1 dozen = 12 units

Temperature...

Fundamentals of Chemistry

Chemistry is the science that studies the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions and its relationship with energy.

Defining Matter and Its Properties

Matter is anything that occupies space, has measurable energy, and is subject to change over time and interactions with measuring devices.

States of Matter

• Solid: If the kinetic energy is less than the potential energy.
• Liquid: If the kinetic and potential energy are approximately equal.
• Gas: If the kinetic energy is greater than the potential energy.
• Plasma: If the kinetic energy is such that the electrons have a positive total energy.

Chemical Elements and Atomic Structure

A Chemical Element is a type of...

The Pluralistic School

Speculation about the physical world, initiated by the Ionians, was continued in the 5th century BC by Empedocles and Anaxagoras. They developed philosophies which replaced the description of a first Ionian substance only by the assumption of a plurality of substances. Empedocles maintained that all things are composed of four irreducible elements: air, water, earth, and fire, combined or separated by two opposing forces as a process of alternation: love and hate. Through this process, the world evolves from chaos to form and back into chaos again, in a repeated cycle. Empedocles considered the eternal cycle as the true object of religious worship and criticized the popular belief in personal gods, but failed to explain...