Investigation 12

The Dynamics of Chemical Reactions and Ocean Acidification

Page 1: Introduction to Chemical Reactions

• Overview of how daily activities impact the Earth.

• Focus on chemical reactions relevant to ocean acidification and climate change, explaining how human-induced activities contribute to increased greenhouse gases leading to ocean temperature rise and acidity.

Page 2: Everyday Activities and Climate Change

• Driving contributes to climate change through carbon emissions; consider other activities like industrial manufacturing, waste disposal, and agriculture.

• Activities affecting Earth’s climate may not be intentional. For instance, deforestation for agriculture not only releases stored carbon but also reduces the planet's capacity to absorb CO2.

• List activities alongside their impacts on the atmosphere or oceans, such as how livestock farming contributes to methane emissions.

Page 3: Formation of Limestone Caves

• Understanding the investigative phenomenon related to limestone caves, noting the role of natural acids like carbonic acid formed from CO2 dissolving in rainwater.

• Engage with multimedia resources for a deeper understanding of speleogenesis (cave formation) and its relation to chemical weathering of limestone.

Page 4: Characteristics of Limestone Caves

• Limestone Caves: Formed through chemical processes like erosion, particularly the dissolution action of acidic water on limestone.

• Evidence gathered from investigations to support claims about cave formations, including the rates of erosion observed in various climates and geological settings.

• Consideration of cause and effect in cave structure stability and change, where increased acidity from environmental changes accelerates erosion.

Page 5: Rates of Reaction

• Definition of Rate: Ratio relating to two quantities over time, emphasizing the factors that affect rates such as concentration, pressure, and temperature.

• Importance of average speed and rates of change in concentration over time. For example, understanding the decay of organic materials influences soil chemistry.

• Applications: Rate calculation from banana ripening as a simple example where ethylene gas concentration increases, speeding the ripening process.

Page 6: Reaction Rates Overview

• Understanding iodine and hydrogen reaction forming hydrogen iodide to illustrate real chemical kinetics.

• Graphs depict changes in concentration over time; initial fast reaction slows, showing how reaction rates can alter based on variables.

• Collision theory: the basis for understanding reaction rates when conditions change, explaining how temperature and concentration affect the frequency of successful collisions.

Page 7: Sample Calculation of Reaction Rates

• Example of calculating the rate of reaction between H2 and I2 with step-by-step instructions.

• Given concentrations and time intervals to illustrate rate calculation; assure that units are consistent in calculations to avoid errors.

• Evaluating results for logical consistency with expectations, prompting students to consider discrepancies and experimental errors.

Page 8: Understanding Reactant Collisions

• Collision Theory: Reactants must collide with proper orientation and sufficient energy. This section will detail energy barriers that need to be exceeded for reactions to occur.

• Incorrect orientation leads to unreactive collisions; adding visual aids can help conceptualize this.

• Some collisions can lead to reaction while others do not due to energy levels, discussing the significance of activation energy and its role in spontaneous reactions.

Page 9: Effect of Concentration on Reaction Rates

• Higher concentration leads to more frequent collisions and faster reaction rates. Include specific examples such as the production of gaseous substances in reactions.

• Illustrations of impacts of reducing volume on gas concentration and reaction rates; explore real-world scenarios such as a gas cylinder's pressure increase and its effect on combustion efficiency.

Page 10: Temperature Effects on Reaction Rates

• Reaction rates increase with temperature due to greater molecular movement and collision frequencies; relate this to seasonal changes affecting chemical processes in oceans.

• Examples illustrating reactions like magnesium with water under different conditions, showcasing how temperature extremes can yield differing products and rates.

Page 11: Effect of Particle Size on Reaction Rates

• Reactions differ based on surface area exposed to reactants; provide comparisons of powdered versus large chunks in practical and industrial contexts.

• Comparison of small vs. large particles in reaction speeds, emphasizing implications for drug formulation and bioavailability.

• Practical applications in industry (e.g., mining, chemical processes) and how optimizing particle size can expedite reactions.

Page 12: Re-evaluating Evidence

• Reflect on initial claims about limestone caves with gathered evidence post-investigation; adapt evidence collection techniques using modern technology like 3D mapping.

• Discuss changes from increased temperatures on cave formation processes, challenging students to predict future impacts based on current data.

Page 13: Energy Transfer in Reactions

• Friction and heat flow described in the context of striking a match, detailing the exothermic nature of combustion.

• Importance of activation energy understood through collision theory, considering how temperature affects the energy distribution of molecules in a reaction.

Page 14: Energy Changes in Reactions

• Overview of energy diagrams representing changes during reactions, highlighting endergonic and exergonic processes.

• Activation energy relevant for forming intermediate products illustrated with clear graphical representations.

Page 15: Multi-step Reactions

• Explanation of one-step vs. multi-step reactions; emphasize how intermediates can affect the rate of the reaction.

• Rate-determining step critical for understanding overall reaction rates