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

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" »

• Lexeme: The abstract vocabulary item listed in the lexicon with a common core of meaning.
• Word-forms: Physical realizations of the lexeme.
• Paradigm: The list of word-forms that belong to a word.
• Morpheme: The smallest unit of analysis with semantic content or grammatical function that words are made up of.
• Morph: The physical realization of the morpheme. Morphs are made up of one or more morphemes.
• Syncretism: Identical word-forms that belong to the same lexeme but are different grammatical words.
• Root: The basic form that remains when you get rid of all the affixes.
• Stem: A term that we only use in inflectional morphology; it is the form to which you attach an inflectional affix (only suffixes in English).
• Base: Anything; any root and any stem are

1.Who propossed the theory of One-dimensional consolidation? Karl Terzaghi

2.What types of permeameters exist in Lab tests? Constant head permeameter and Failing head permeameter

3.What is the name of the equation that Governs the 2D underground flow? Laplace’s Equation.

4.Name of the method of draw flow nets That uses iterative calculations. Finite Differences

5.What are the units of the compression Index Cc? Adimensional, NOT UNITS

6.Describe boiling in soils. Boiling of soils occurs when there is an Upward flow and the seepage force is greater that the submerged weight of the Soil.

7.What are the assumptions in laplace’s Equation. Darcy’s law applies, Water and Solids are uncompressible

8.When in it better to use failing head permeameter?

Q#9.1: How order of reaction is experimentally determined.

Ans. Order of reaction is determined by the following two methods.

1. From Rate Law.

   In this method, the rate of reaction is measured using chemical and physical methods (volumetric, gravimetric, spectrophotometer, pH-meter, conductometric methods). The dependence of the rate of reaction on the concentration of reactants tells us about the order of reaction. For example, a reaction in which the rate of reaction doubles when the concentration of reactants is doubled will be of first order. If the rate increases four times by doubling the concentration, the reaction will be of second order.

2. Ostwald’s Isolation Or Large Excess Method.

   This method is used to determine the order of complicated

Photoelectric Effect Explained

The photoelectric effect is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner are called photoelectrons.

Specifically, when light shines on a metal, electrons can be ejected from its surface. This phenomenon, where light waves hitting a metal surface cause electrons to be ejected, is a fundamental aspect of the photoelectric effect.

Chemical Bonds: Types and Strengths

Understanding Chemical Bonds: Strongest to Weakest

Chemical bonds are the forces that hold atoms together to form molecules. Here are three types, generally ordered from strongest to weakest:

1. Ionic Bonding

   Ionic bonding involves a transfer of an electron, where one atom gains an electron while