Module5-Chemical-Reactions-chemical-change.pptx

science

1. MODULE 5: Chemical Change

2. Objectives At the end of the lesson I will be able to… Use simple collision theory to explain the effects of concentration. Temperature, and particle size on the rat of reaction. Recognize that energy is released or absorbed during a chemical reaction. Define catalyst, and describe how it affects the reaction rate.

3. Exploring Chemical Reactions This presentation explores the fundamentals of chemical reactions, from basic concepts to factors influencing their rates and energy changes. Let's dive in!

4. Reactants and Products Reactants Substances present at the start of a reaction. Products Substances formed as a result of the reaction.

5. Factors Influencing Reactions Collision theory explains how reactions occur. Collision Frequency The more frequently molecules collide, the faster the reaction. Collision Energy Only collisions with enough energy can overcome activation energy. Orientation Molecules must collide in the correct orientation for a reaction to occur.

6. Factors Influencing Reactions 1 Temperature Higher temperatures generally increase reaction rates. 2 Concentration Increasing reactant concentration typically speeds up reactions. 3 Surface Area Greater surface area of reactants allows for more frequent collisions. 4 Catalyst A substance that speeds up a reaction without being consumed.

7. Reaction Rate Factors Temperature Higher temperatures increase the frequency and energy of collisions. Catalyst Provides an alternate pathway with lower activation energy. Concentration More reactants mean more opportunities for collisions. Surface Area Greater surface area allows for more frequent collisions.

8. Energy Changes 1 Activation Energy Energy required to start a reaction. 2 Enthalpy Change Energy difference between reactants and products. 3 Exothermic Releases energy. 4 Endothermic Absorbs energy.

9. Chemical Reactions in Action Cooking Chemical reactions transform ingredients during cooking. Rusting Iron reacts with oxygen and water to form rust. Combustion Burning fuel releases energy through chemical reactions. Photosynthesis Plants convert light energy into chemical energy.

10. Exothermic Reactions These reactions release energy into the surroundings, often manifesting as heat. 1 Heat Production The energy released raises the temperature of the surroundings. 2 Energy Decrease The products have lower energy than the reactants. 3 Common Examples Combustion, neutralization reactions.

11. Endothermic Reactions These reactions absorb energy from the surroundings, often causing a decrease in temperature. Energy Absorption The products have higher energy than the reactants. Cooling Effect Energy absorbed from the surroundings leads to a decrease in temperature.

12. Group Work Research:   Students will work in groups to research and present examples of chemical changes that occur in daily life, identifying the evidence of chemical change and its real-world significance.   Questions: What are the observable signs of the chemical change? What is the chemical change in your chosen example? What are the reactants and products of the change? Why is this chemical change important or significant in everyday life?

13. Collision Theory: Concentration When you increase the concentration of hydrochloric acid (HCl) in a solution reacting with zinc (Zn) , the reaction rate increases. According to collision theory , as you add more HCl, there are more HCl molecules in the solution. This means that the zinc particles collide with acid molecules more often, leading to a faster rate of reaction and more hydrogen gas being produced.

14. Collision Theory: Temperature When you heat up a solution of sodium thiosulfate and hydrochloric acid , the reaction speeds up. According to collision theory , increasing the temperature gives the particles more energy . This causes the particles to move faster and collide more frequently and with more force, increasing the chances of successful collisions. As a result, the reaction happens more quickly, and you can see the solution turn cloudy faster.

15. Collision Theory: Particle size on the rate of reaction When powdered calcium carbonate ( CaCO ₃) reacts with hydrochloric acid (HCl), it reacts faster than when larger chunks of calcium carbonate are used. According to collision theory , smaller particles have a larger surface area . This means more particles are exposed to the acid, leading to more frequent and successful collisions between the acid and calcium carbonate. As a result, the reaction happens faster with powdered calcium carbonate compared to larger pieces.

16. Question: How can you recognize if energy is released or absorbed during a chemical reaction? Give an example.

17. Question: What is a catalyst, and how does it affect the reaction rate?

18. Key Takeaways Chemical reactions are fundamental to our world, from everyday processes to complex biological functions. By understanding the factors influencing their rates and energy changes, we gain valuable insights into how our world works. This knowledge empowers us to harness chemical reactions for various applications, including energy production and innovative material development.

19. Assignment: (Group Activity) O bserve, analyze, and understand the signs and characteristics of chemical changes by conducting hands-on experiments. Assign or Choose Topics: Each group will research one of the following topics (or choose their own with teacher approval): Cooking and baking (e.g., baking bread or frying an egg) Rusting of metals (e.g., rusting of iron tools) Combustion (e.g., burning of wood or fuels) Food spoilage (e.g., milk turning sour)

20. Assignment: (Group Activity) Research Questions: Each group should answer the following questions during their research: What is the chemical change occurring in your chosen example? What are the observable signs of the chemical change? What are the reactants and products of the change? Why is this chemical change important or significant in everyday life? Presentation: Each group will prepare a short presentation (5–7 minutes) to share their findings with the class. Encourage creativity—groups can use posters, slides, demonstrations, or role-play to explain their topic.