Notes, summaries, assignments, exams, and problems for Chemistry

From Dalton to the Electron

The simple model set by Dalton needed updating. In 1894, Crookes discovered that cathode rays were produced just by applying a very high voltage between two electrodes. He observed that he could get a shadow, so his conclusion was that "some particles exit from the metal plate placed in the cathode." As those particles were attracted by the positive electrode, the so-called cathode rays had to have a negative charge. Thomson (1897) interpreted the experiment as showing that cathode rays were a stream of electrons. Atoms, as introduced by Dalton, were not indivisible. Since electrons were issued from a metal, atoms were made of electrons (negative charge) and something else with a positive charge because matter is... Continue reading "Atomic Structure: From Dalton to Rutherford" »

This document outlines fundamental laws, key concepts, and various types of chemical reactions crucial for understanding the principles of chemistry. Each point provides a concise definition, serving as a quick reference for core chemical knowledge.

Fundamental Chemical Laws and Concepts

1. Law of Conservation of Mass

   Mass is neither created nor destroyed in a chemical reaction; it remains constant.

2. Law of Definite Proportions

   A compound always contains the same elements in the same proportion by mass.

3. Law of Multiple Proportions

   Elements combine in small, whole-number ratios to form different compounds.

4. Gay-Lussac's Law of Gaseous Volumes

   The volumes of reacting gases (at constant temperature and pressure) are in simple whole-number ratios.

5. Newlands' Law

1- Explain the process of making monomers and polymers.

Monomers are small subunits that when bound together form polymers

Polymers are formed by either dehydration or by hydrolysis

2- Define Cytoskeleton with its characteristics.

Structural framework consist of protein tubules, filaments: Microtubules, Microfilaments, Intermediate filaments

3- What is another name for protein channel that link cells?

Adhesion proteins – permit cell to stick together

4- What are the characteristics of phospholipids

Each phospholipid contains head and tail (head is hydrophilic, means it is attracted to water; the tails is hydrophobic, repels water)

5- What is the primary component of a cell membrane made of?

Phospholipids (glycerol bond, 2 fatty acids, phosphate group)... Continue reading "General Biology Test: Questions and Answers" »

Fossil Fuels: Formation and Combustion

How Fossil Fuels Are Formed

Fossil fuels, including natural gas, petrol (gasoline), and coal, are formed from the remains of ancient living organisms over millions of years. These vital energy sources are primarily compounds of carbon and hydrocarbons.

Combustion of Fossil Fuels

The combustion of fossil fuels always produces carbon oxides and water. However, due to impurities present in these fuels, the burning process can sometimes release dangerous gases into the atmosphere.

Respiration: A Biological Combustion

A slow combustion reaction also takes place within the human body, known as respiration. The energy required for life is released when glucose reacts with the oxygen we breathe. This fundamental biological... Continue reading "Fossil Fuels, Dynamite, and Chemistry's Pioneers" »

Relative Molecular Mass and Composition

60.The relative molecular mass of aluminium chloride is 267 and its composition by mass is 20.3%....

moles of Na == 0.05;

moles of NaOH = 0.05; same as moles of Na.concentration == 0.20 (mol dm–3)3

Reaction of Sodium with Water

61.Sodium reacts with water as follows.2Na(s) + 2H2O(l)  2NaOH(aq) + H2(g)

1.15 g of sodium....

AlCl .empirical formula AlCl3;molecular formula: n = = 2;Al2Cl6

Reaction of Calcium Carbonate with Acids

62.(i)Calcium carbonate is added to separate solutions of hydrochloric acid and ethanoic.....bubbling/effervescence/dissolving of CaCO3/gas given off 

more vigorous reaction with HCl/OWTTE;2

(ii)2HCl(aq) + CaCO3(s)  CaCl2(aq) + CO2(g) + H2O(1); 

(iii)amount of CaCO3.amount of HCl... Continue reading "Chemical Reactions and Energy Changes" »

Pure Substances and Mixtures

Pure substances: A pure substance has a constant composition that does not vary when subjected to physical changes.

Mixtures: A mixture can be separated by physical changes, such as filtering or boiling.

Elements and Compounds

Element: An element is a pure substance consisting of a single type of atom.

Compound: A compound is a pure substance consisting of two or more types of atoms linked together by chemical bonds.

Composition of the Universe, Earth, and Humans

• Universe: Hydrogen (73.9%), Helium (24%), Other (2%)
• Earth: Oxygen (29.7%), Iron (31.9%), Silicon (16.1%), Magnesium (15.4%), Other (6.4%)
• Human Being: Oxygen (65%), Carbon (18%), Hydrogen (10%), Nitrogen (3%), Other (3.4%)

The Periodic Table

Periodic Table: The periodic... Continue reading "Elements, Compounds, and the Periodic Table" »

Unit 1: Memory and Experience Vocabulary

Key Vocabulary for Memory and Recollection

• remember: recordar
• recall: traer de la memoria
• record: grabar
• appointments: citas
• diary: diario
• memorize: memorizar
• memory: memoria
• memories: recuerdos
• calendar: calendario
• remind: recordar
• mind: mente
• forget: olvidar
• learn: aprender
• by heart: de memoria

Phrasal Verbs Related to Action and Resolution

• carry out: llevar a cabo
• let something down: decepcionar
• sort out: ordenar/preparar
• work out: resolver

Common False Friends in English

• anxious: nervioso vs. eager: ansioso
• success: éxito vs. event: suceso
• embarrassed: avergonzado vs. pregnant: embarazada

Expressing Feelings and Emotions

Intensity of Feelings: From Mild to Strong

• angry/cross → furious
• upset → heartbroken/devastated
• frightened/

Atom

The smallest particles a simple substance can be divided into without losing its chemical properties.

Chemical Element

A chemical element is a species of atoms having the same number of protons in their atomic nuclei.

Subatomic Particles

• Electrons: negative charge, no mass
• Protons: positive charge, mass
• Neutrons: no charge, mass equal to protons.

Atomic Models

• Plum Pudding Model: a sphere of positive electricity with neutrons
• Rutherford's: each electron had an orbit
• Bohr's: each orbit presents a different number of electrons.

To differentiate an atom from others, the number of protons and neutrons it has in its nucleus.

Atomic Number

Number of protons in the nucleus of an atom (Z).

Mass Number

The number of protons and neutrons in the nucleus of an atom... Continue reading "Understanding Atoms, Elements, and Bonds in Chemistry" »

Matter: pure substances: element and compound

           mixture: homogeneous mixture and heterogeneous mixture

A pure substance is a substance made of only one kind of matter and having definite properties. An element is composed of a ingle kind of atoms. A compound is composed of two or more elements in a specific ratio. Chemists cant easily separate the components of a compound. Mixtures are physical combinations of pure substances. Different parts of a mixture can be easily separated by physical means. A heterogeneous mixture is a mixture whose composition varies from position to position within the sample. A homogeneous mixture sometimes called solution is relatively uniform in composition. Solvent and solute.

State: solid Solvent:... Continue reading "Coh3 compound name" »