Chemical Reactions Study Guide 2 PDF

Chemical Reactions  Focus Question How are chemical reactions modeled?  New Vocabulary chemical reaction reactant product chemical equation coefficient  Review Vocabulary chemical change: a process involving one or more substances changing into a new substan...

Chemical Reactions  Focus Question How are chemical reactions modeled?  New Vocabulary chemical reaction reactant product chemical equation coefficient  Review Vocabulary chemical change: a process involving one or more substances changing into a new substance  STATES OF MATTER Vibrate in position Restricted movementUnrestricted movement V close close v far apart Rigid container container None none yes Fastest fast slowest Most Little none  CHANGE OF STATES freezing solidification melting sublimation condensation COMPLETE THIS  BROWNIAN MOTION Brownian motion refers to the random, erratic movement of microscopic particles suspended in a fluid (either liquid or gas). This motion is caused by the constant collisions of the suspended particles with the fast-moving molecules of the fluid itself.  BROWNIAN MOTION Mechanism of Brownian Motion: Collisions with Molecules: Brownian motion occurs because particles suspended in a fluid are constantly bombarded by the molecules of the surrounding medium. These molecules are in continuous, random motion due to thermal energy, and when they collide with the suspended particles, they impart small amounts of momentum. Random Motion: Since the collisions happen in all directions and at varying speeds, the movement of the suspended particles appears random and unpredictable.  KEY FACTORS INFLUENCING BROWNIAN MOTION Temperature: Higher temperatures increase the kinetic energy of the fluid molecules, leading to more vigorous collisions and faster Brownian motion. Viscosity of the Medium: A more viscous medium (thicker fluid) slows down the particles, reducing the intensity of Brownian motion. Particle Size: Smaller particles are more strongly affected by Brownian motion because they are lighter and easier for the fluid molecules to move.  TYPES OF FORMULA ▪ Empirical: ▪ The ratio of the atoms of each element in a compound in its lowest terms ▪ Molecular: ▪ The number of atoms of each element in a molecule  Chemical Reactions The process by which the atoms of one or more substances are rearranged to form different substances is called a chemical reaction. A chemical reaction is another name for a chemical change.  Chemical Reactions Evidence of a Chemical Reaction A temperature change can indicate a chemical reaction. Many reactions release energy in the form of heat and light. Other chemical reactions absorb heat. Color change can indicate a chemical reaction. Odor, gas bubbles, and the formation of a solid are other indications of chemical change.  Representing Chemical Reactions Equations are used to represent chemical reactions. Equations show a reaction’s reactants (starting substances) and products (substances formed). The table shows the symbols used in chemical equations.  Representing Chemical Reactions Word Equations aluminum(s) + bromine(l) → aluminum bromide(s) In this word equation, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide.” Word equations lack information about the number of atoms involved.  Representing Chemical Reactions Skeleton Equations Al(s) + Br(l) → AlBr3(s) Skeleton equations use symbols and formulas to represent reactants and products. These equations also lack information about the number of atoms involved.  Representing Chemical Reactions Chemical Equations A chemical equation uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.  Balancing Chemical Equations A coefficient in a chemical equation is the number written in front of a reactant or product.  Balancing Chemical Equations Steps for Balancing Equations 1. Write the skeleton equation for the reaction. 2. Count the atoms of the elements in the reactants. 3. Count the atoms of the elements in the products. 4. Change the coefficients to make the number of each element equal on both sides of the equation. This shows that atoms are conserved. 5. Write the coefficients in their lowest possible ratio. 6. Check your work.  Quiz 1. Which of the following is not an example of a chemical reaction? A rusting iron B burning wood C boiling water CORRECT D rotting food  Quiz 2. Which of the following is not true about coefficients in a balanced chemical equation? A They are numbers C They describe the written in front of highest whole number reactants or products. ratio of the amounts of all reactants and products. CORRECT B They are usually whole D They are not usually numbers. written if the value is 1.  Quiz 3. Which observation is NOT physical evidence that a chemical reaction has occurred? A There is an odor change. B A solid is no longer magnetic. C A solid melts. CORRECT D A solid changes color.  Quiz 4. Which of the following is NOT true about balancing chemical equations? A Subscripts should never C Coefficients are changed be changed to balance to make the number of the equation. each element equal on both sides. B Coefficients are written D Subscripts are changed in their lowest possible to make the number of ratio. each element equal on both sides. CORRECT