22 Matching Annotations
  1. Jun 2020
    1. Figure 6.1.46.1.4\PageIndex{4}: Temperature versus heat. The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in the system. The long stretches of constant temperatures at 0oC0oC0^oC and 100oC100oC100^oC reflect the large amounts of heat needed to cause melting and vaporization, respectively.

      Figure 6.1.4 : Temperature versus heat. The system is constructed so that no vapor evaporates while ice warms to become liquid water, and so that, when vaporization occurs, the vapor remains in the system. The long stretches of constant temperatures at 0oC and 100oC reflect the large amounts of heat needed to cause melting and vaporization, respectively.

    2. Heat and work have signs (positive or negative), and the sign of each depends on whether the system we are considering is gaining or losing energy. In this class, if a process makes the system gain energy, qqq and/or www are positive; if the process makes the system lose energy, qqq and/or www are negative. We can put this information into four formal statements: If heat flows into a system, qqq is positive. If heat flows out of a system, qqq is negative If the surroundings do work on the system, www is positive. If the system does work, www is negative.

      Heat and work have signs (positive or negative), and the sign of each depends on whether the system we are considering is gaining or losing energy. In this class, if a process makes the system gain energy, q and/or w are positive; if the process makes the system lose energy, q and/or w are negative. We can put this information into four formal statements:

      • If heat flows into a system, q is positive.
      • If heat flows out of a system, q is negative
      • If the surroundings do work on the system, w is positive.
      • If the system does work, w is negative.
    3. In order to measure energy, we need a unit for it. In the metric system, the standard unit of energy is the joule. The formal definition of a joule is: A joule is the amount of energy expended when an object is moved 1 meter against a resisting force of 1 newton. (You can learn all about the concept of force in a physics class.) As for the joule, here are some statements that may help you visualize this unit.  A joule is… …enough energy to lift a one kilogram object 10.2 centimeters. …enough energy to heat one milliliter of water from 20ºC to 20.24ºC. …enough energy to keep a 60 watt light bulb glowing for 0.0167 seconds. Obviously, a joule is a very small amount of energy, and in fact it is an inconveniently small amount when we describe chemical reactions. Chemists usually report energies for reactions in kilojoules (1 kJ = 1000 J).

      In order to measure energy, we need a unit for it. In the metric system, the standard unit of energy is the joule. The formal definition of a joule is: A joule is the amount of energy expended when an object is moved 1 meter against a resisting force of 1 newton. (You can learn all about the concept of force in a physics class.) As for the joule, here are some statements that may help you visualize this unit. A joule is…

      …enough energy to lift a one kilogram object 10.2 centimeters.

      …enough energy to heat one milliliter of water from 20ºC to 20.24ºC.

      …enough energy to keep a 60 watt light bulb glowing for 0.0167 seconds.

      Obviously, a joule is a very small amount of energy, and in fact it is an inconveniently small amount when we describe chemical reactions. Chemists usually report energies for reactions in kilojoules (1 kJ = 1000 J).

    1. In any electrochemical process, electrons flow from one chemical substance to another, driven by an oxidation–reduction (redox) reaction. A redox reaction occurs when electrons are transferred from a substance that is oxidized to one that is being reduced. The reductant is the substance that loses electrons and is oxidized in the process; the oxidant is the species that gains electrons and is reduced in the process. The associated potential energy is determined by the potential difference between the valence electrons in atoms of different elements.
    1. Theoretical Yields When reactants are not present in stoichiometric quantities, the limiting reactant determines the maximum amount of product that can be formed from the reactants. The amount of product calculated in this way is the theoretical yield, the amount obtained if the reaction occurred perfectly and the purification method were 100% efficient. In reality, less product is always obtained than is theoretically possible because of mechanical losses (such as spilling), separation procedures that are not 100% efficient, competing reactions that form undesired products, and reactions that simply do not run to completion, resulting in a mixture of products and reactants; this last possibility is a common occurrence. Therefore, the actual yield, the measured mass of products obtained from a reaction, is almost always less than the theoretical yield (often much less). The percent yield of a reaction is the ratio of the actual yield to the theoretical yield, multiplied by 100 to give a percentage: percent yield=actual yield (g)theoretical yield(g)×100%(3.7.29)
    1. What happens to matter when it undergoes chemical changes? The Law of conservation of mass says that "Atoms are neither created, nor distroyed, during any chemical reaction." Thus, the same collection of atoms is present after a reaction as before the reaction. The changes that occur during a reaction just involve the rearrangement of atoms.
    2. C7H16(l)+O2(g)→CO2(g)+H2O(g)(3.1.4)(3.1.4)C7H16(l)+O2(g)→CO2(g)+H2O(g) C_7H_{16} (l) + O_2 (g) \rightarrow CO_2 (g) + H_2O (g) \label{3.1.3} The complete combustion of any hydrocarbon with sufficient oxygen always yields carbon dioxide and water. Figure 3.1.23.1.2\PageIndex{2}: An Example of a Combustion Reaction. The wax in a candle is a high-molecular-mass hydrocarbon, which produces gaseous carbon dioxide and water vapor in a combustion reaction (see Equation 3.1.43.1.4\ref{3.1.3}). Equation 3.1.43.1.4\ref{3.1.3} is not balanced: the numbers of each type of atom on the reactant side of the equation (7 carbon atoms, 16 hydrogen atoms, and 2 oxygen atoms) is not the same as the numbers of each type of atom on the product side (1 carbon atom, 2 hydrogen atoms, and 3 oxygen atoms). Consequently, the coefficients of the reactants and products must be adjusted to give the same numbers of atoms of each type on both sides of the equation. Because the identities of the reactants and products are fixed, the equation cannot be balanced by changing the subscripts of the reactants or the products. To do so would change the chemical identity of the species being described, as illustrated in Figure 3.1.33.1.3\PageIndex{3}. Figure 3.1.33.1.3\PageIndex{3}: Balancing Equations. You cannot change subscripts in a chemical formula to balance a chemical equation; you can change only the coefficients. Changing subscripts changes the ratios of atoms in the molecule and the resulting chemical properties. For example, water (H2O) and hydrogen peroxide (H2O2) are chemically distinct substances. H2O2 decomposes to H2O and O2 gas when it comes in contact with the metal platinum, whereas no such reaction occurs between water and platinum. The simplest and most generally useful method for balancing chemical equations is “inspection,” better known as trial and error. The following is an efficient approach to balancing a chemical equation using this method.
  2. Mar 2018
  3. Mar 2017
    1. Protection Level 0 Limited or none Information intended for public access, e.g.,: Public directory information

      Includes name and email.

    2. Student Directory Data (link is external) (unless the student has requested that information about them not be released as public information) Name of student Address, telephone, e-mail

      Not considered private or high level?

    3. Evaluations

      Anything graded with grade indicated? Or simply gradeable?

  4. Sep 2015
    1. la universalidad no consiste, por lo que se me alcanza, en la natura­leza o concepto absoluto, positivo de una cosa, sino en la relación que guarda con los particulares significados o re­presentados por ella

      La universalidad no consiste en la naturaleza del concepto general sino en la relación lógica que guarda con los conceptos particulares.

    2. del mismo modo que esta linea particu­lar se convíerte en general al hacerse de ella un signo, el nombre linea, que tomado en sentido absoluto es particu­lar, al ser un signo se coD.víerte en ge

      La generalidad consiste en el signo.

    3. una idea, que considerada en sí misma es particular, se convíerte en general al hacerla representar o significar a todas las demás ideas particulares del mismo tipo.

      Las ideas generales, según Berkeley.

    4. Acepción exacta de la abstrac­ción. Todo el mundo está de acuerdo en que las cualidades o modos de las cosas nunca existen realmente cada una de ellas aparte por si misma y separada­mente de todas las demás, sino todas ligadas y mezcladas, por decirlo asi, varias. en el mismo objeto. Pero, se nos dice,. como la mente es capaz de consi­derar cada cualidad aisladamente, o abstraída de aquellas otras cualidades con las que está unida, construye de este modo para si misma ideas abstrac­tas.

      Definición de la abstracción por omisión.

    5. Tratado sobre los principios del conocimiento humano

      Berkeley, Tratado sobre los principios del conocimiento humano

  5. Dec 2014
    1. Some protesters also sat on a train track in Berkeley, blocking a train from moving, the San Francisco Bay Guardian reported.

      The Bay Guardian had already been shut down at the time of writing. The author was confused by out-of-date information in the bio of former Bay Guardian news editor Rebecca Bowe.

  6. Aug 2013
    1. One thing that’s been clear to us from the start is that getting the world to adopt new technologies, tools and workflows is hard. We think inattention to this has been one of the primary reasons why

      BERKELEY