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Energy and Chemical Change

Measuring and calculating the energy involved in chemical changes. Energy and Chemical Change. Record the temperature of 5 ml 5M HCl . Record the temperature of 5 ml 5M NaOH . Add HCl + NaOH  Record the temperature of the final solution. Write the equation. (both solutions are ( aq )

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Energy and Chemical Change

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  1. Measuring and calculating the energy involved in chemical changes Energy and Chemical Change

  2. Record the temperature of 5 ml 5M HCl. • Record the temperature of 5 ml 5M NaOH. • Add HCl + NaOH • Record the temperature of the final solution. • Write the equation. (both solutions are (aq) • What evidence do you have that a chemical reaction has taken place? Does a temperature change occur when a chemical reaction takes place?

  3. Potential Energy Kinetic Energy • Energy is defined as the ability to do work or produce heat. • SI unit for energy is Joules (J). • There are 2 types of energy Energy

  4. 1. Potential Energy (PE) • Energy that is based on an object’s composition (chemical PE) or position; associated with attractions and repulsions. • Chemical potential energy • the energy stored in a substance because of its composition (ex: plants, gasoline) • plays an important role in chemical reactions Energy

  5. 2. Kinetic Energy (KE) - Energy of motion. • Can be measured as temperature or heat. • Temperature-the measure of the average kinetic energy • Heat-energy transferred from warmer objects to cooler objects. • KE of a substance is directly related to the motion of its atoms and temp. • KE = ½ mv2 Energy

  6. * Every object has either potential or kinetic energy!!! Energy

  7. Law of Conservation of Energy: energy can be converted from one form to another, but it is neither created nor destroyed. Energy

  8. Form of energy that transfers from warmer objects to cooler objects. • An object’s temperature increases because energy is transferred into it. Temperature is a measure of the average kinetic energy of the particles in a sample of matter; it does not depend on the amount of matter in the sample. Heat

  9. The heat (energy) transfer occurs when 2 objects of different temperatures are brought into contact to reach equilibrium. • Depends on the mass of the sample. • Symbol = m Unit = grams • Reactions can be endothermic (heat/energy in) or exothermic (heat/energy out). Heat

  10. There are many units that can express an amount of energy. • calorie (cal) - amount of heat required to raise the temperature of 1.00 g of pure water by 1oC. How Can I Measure Energy/Heat?

  11. kilocalorie (kcal) - 1000 calories or one Calorie – this is one food Calorie! • Joule - SI unit of heat and energy. (What we will mainly use) Important conversions: 1 Calorie = 1 kcal 1 kcal = 1000 cal 1 cal = 4.184 J How Can I Measure Energy/Heat?

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