sci mod.4

• Collision Theory


  Atoms or molecules must collide with enough energy in order to react
• Reactants in a chemical reaction must collide to form a new product
• Pukpok Palayok game


  • Player holding a stick hits the pot, resulting in the release of items inside
• When the stick hits the pot

  The pot will break, releasing items inside
• Energy is needed to break the pot
• Collision


  1. Stick hits pot

  2. Pot breaks

  3. Items released from pot
• Reactant molecules must come together in a collision in order to react and produce new molecules
• Activation energy


  Minimum energy required for a reaction to occur

  
• Activation energy is needed to break the bonds of the reactants to form new products or new substances
• Chemical industries study ways to manufacture products faster without sacrificing quality
• Food industries look for ways to slow down reactions, thus, slow food spoilage
• Factors that affect the speed or rate of chemical reactions

  • Particle size or surface area of reactants
  • Concentration of the reactants
  • Temperature
  • Presence of catalyst

  
• Activity 1. The Rate of Dissolving Detergent Bar and Powder


  1. Get two identical containers and fill with water

  2. Put detergent bar and powder in each container

  3. Stir after 2 minutes and observe
• Particle size or surface area

  Smaller pieces have greater surface area, providing more contact and collisions between reactants
• Concentration


  Measure of the number of particles of solute in a solution
• Increased concentration


  Increases corrosion rate
• Temperature


  Higher temperature increases particle movement and collision frequency, providing more activation energy for reactions
• Decreasing temperature lowers the rate of food spoilage
• Catalyst


  Substance that alters the rate or speed of a chemical reaction
• Catalyst


  Alters the speed of reaction by changing the activation energy

  
• Enrichment Activity 1


  Identify which situation would have a higher reaction rate and state the factor affecting the rate

  
• Enrichment Activity 2


  Read situations on how rates of chemical reaction are applied and answer the guide question

  
• Corrosion


  Deterioration of substances, an electrochemical process
• Rusting is the common term for corrosion of iron and its alloys such as steel
• Higher temperature


  Steel and other metals corrode at a faster rate
• Statues made from calcium carbonate such as limestone and marble typically wear out slowly over time due to air pollutants
• The presence of pollutants like sulfur dioxide results in the formation of acid rain, resulting in the wearing out of the statues
• As the concentration of pollutants increases

  Deterioration of limestone occurs more rapidly
• American Astronauts died during the 1967 tragedy of Apollo I due to a flash fire that occurred inside the command module that contained 100 percent oxygen
• Gas Laws


  • Dalton's Law
  • Charles's Law
  • Boyle's Law
  • Gay-Lussac's Law
  • Combined Gas Laws
  • Graham's Law
  • Ideal Gas Law
• Boyle's Law


  The volume of a fixed mass of gas varies inversely with the pressure at constant temperature

  
• Boyle


  • Born into aristocratic Irish family
  • Interested in medicine and science of Galileo
  • Studied chemistry
  • Prolific writer on science, philosophy, and theology
  • Champion of performing controlled experiments and keeping and publishing detailed records
• Boyle's Experiments


  Examined changes in volume of gas under different pressures
• Boyle's Experimental Results


  • Pressure (atm): 8, 4, 2, 1

  Volume (L): 2, 4, 8, 16

  Pressure and volume are inversely proportional

  
• Boyle's Law: P1V1 = P2V2
• Boyle's Law


  • Pressure and volume move in opposite directions

  Pressure up - Volume down

  High pressure - Low volume

  Low pressure - High volume
• Inverse proportion


  Relationship between two variables where the product is a constant
• Boyle's Law Demonstrated


  • Using a piston and weight, as pressure increases, volume decreases
• As gas is compressed, its molecules strike the walls of the container more frequently, raising pressure
• Freon-12 Example


  • Initial conditions: P1 = 50 mm Hg, V1 = 1.6 L

  Final conditions: P2 = 200 mm Hg, V2 = 0.4 L