Exploring Energy Forms and Transformations in Science

1. Chapter 2 The Human Organism and the Power of Energy

2. Lesson 2.1 Energy Types and Transformations

3. ENERGY • ENERGY is the capacity to do work or cause a change • There are many forms of energy • Some forms of energy are listed on the next slide • All forms of energy can be measured in JOULES • The main unit of energy is the Joule (J). • A Joule is the amount of energy it takes to lift a Newton (about 100g) one metre. • 1000 Joules = 1 kilojoule (kJ)

4. Some Forms of Energy These are the 4 energy forms that we will study in more detail.

5. THERMAL ENERGY • Thermal energy comes from the random motion of the particles (Temperature of molecules) that make up a substance and the amount of particles (mass). • The faster the molecules of a substance move, the hotter the substance seems to us. Really fast molecules can even make flames! ColdWarmHot As you can see, even in solids, the molecules vibrate a bit

6. RADIANT ENERGY • Radiant Energy is contained in, and transported by electromagnetic waves • Light is the most obvious form of radiant energy • The shorter the wavelength the greater the energy • Other forms of radiant energy include: • X-Rays • Radio Waves • Ultraviolet Rays • Infra-red Radiation (radiated heat) • Gamma rays, cosmic rays (powerful radiation)

7. CHEMICAL ENERGY • CHEMICAL ENERGY is stored in the bonds of molecule or by forming bonds. • Like the energy in gasoline, or wood that you burn, or any other form of fossil fuel. • Also, the energy used by life, such as the energy in food, is chemical energy.

8. MECHANICAL ENERGY • MECHANICAL ENERGY results from the speed and mass of an object, and from its relationship to its surroundings. • In other words, mechanical energy comes from the movement of objects. • Falling objects, moving vehicles, mechanical devices and spinning wheels all have mechanical energy.

9. ENERGY TRANSFORMATION • ENERGY TRANSFORMATION is changing energy from one form to another • Examples: • Radiant  to  Thermal (sun warms ground) • Chemical  Radiant  Thermal (burning causes light & heat) • Radiant  to  Chemical (photosynthesis) Heat (thermal energy) Radiant Radiant (light) Flame (radiant energy) Food (chemical) Log (chemical energy) Thermal (heat)

10. Assignments on Energy Types and Transformations • Textbook pp. • Workbook pp.23 to 26

11. Lesson 2.2 How energy causes changes in matter

12. Changes and Energy • Energy can cause changes in matter, and changes in matter can produce energy.

13. Types of Changes: Two Types of Changes Physical Change Chemical Change

14. Physical Change: • Does not change the chemical composition of a substance. It does not affect the nature or characteristic properties of the substance. • Process is sometimes* reversible for changes of state • Ex. Crumpling & smoothing out paper • Ex. Freezing water and thawing ice • Ex. Sublimation – from solid to gas (ex. dry ice (CO2) or iodine) *there are a few physical changes that are difficult to reverse.

15. Tells you a physical change occurred • Physical Change Key Words: • Crush/PulverizePhysical change • Melt (Fusion)Physical change • Evaporation Physical change Condensation Physical change Sublimation Physical change • Solidification Physical change • Dissolve Physical change

16. Energy and Change of State(some people say “Phase” instead of “State”) • Adding thermal energy to an object makes its particles (ie. Atoms or Molecules) move faster. • If the particles move fast enough, the substance may change state, going from solid to liquid or from liquid to gas. • Change of state is a PHYSICAL change caused by changing the amount of thermal energy in a substance

17. Physical Changes of State Absorbs Energy GAS Releases Energy They just move faster (or slower) DEPOSITION (solid sublimation) When a substance changes state it is always a physical change! Its molecules don’t change SUBLIMATION (gaseous) CONDENSATION (liquid) VAPORIZATION (evaporation) FUSION (Melting) SOLID LIQUID SOLIDIFICATION(Freezing)

18. Chemical Changes: • Changes the chemical composition or make-up of the substance • New substances are formed with new properties • Not easily reversible (Reversible only through chemical means or reactions) Rust

19. Tells you a chemical change occurred Signs of Chemical Changes: • Formation of a new gas when two substances mix. • Formation of a precipitate from mixing two solutions. • A significant change in colour when materials react. • Release of heat &/or light when materials are mixed • Increase or decrease in mass

20. Be Careful! • Pay attention to the “when” part of each clue. • Eg. “It is a chemical reaction if gas is released when two materials mix” • One of these is definitely a chemical change, the others are not: • 1) Gas bubbles are released when a pop bottle is opened • 2) Gas bubbles are released when vinegar and baking soda mix. • 3) Gas bubbles are released when water boils. #2 is the chemical change. #1 is not, since the release of gas is due to pressure change. #3 is not, since it is a change of state (liquid to gas)

21. Be Careful! • Pay attention to the “when” part of each clue. • “It is a chemical reaction if a significant change in colour occurs when materials react.” • One of these is definitely a chemical change, the others may not be: • 1) Base added to phenolphthalein changes it from clear to bright purple-pink. • 2) Wet blue jeans look darker than dry ones. • 3) Mixing yellow and blue paint makes green paint. #1 is the chemical change. #2 is not, since the colour change is not significant. #3 is not, since it is a simple blending of existing colours, not a reaction.

22. Chemical Change: Synthesis • The formation of a complex molecule out of atoms or simpler molecules. • Reactants Products Synthesis H H H H O O H H O O H H become 2 H2O Two more complex molecules O2 + 2 H2 Three simple molecules

23. Chemical Change: Decomposition • When complex molecules are transformed into simpler molecules or atoms Al Al O O O O O O Al Al O O Al Al O O Al Al O O 4 Al + 3 O2 Seven simpler molecules or atoms Become... 2 Al2O3 two complex molecules

24. Chemical Change: Oxidation • When oxygen combines with a material to change it. • rusting of iron or corrosion of any metal is an example of slow oxidation. • Combustion or burning is an example of rapid oxidation. Note: This type of oxidation is also a synthesis. Some oxidations may be decomposition. 4 Fe + 3O2 2Fe2O3 C + O2 CO2 Fuel

25. Chemical Change: Precipitation • In chemistry, precipitation is the formation of a solid that is insoluble following the mixing of two solutions • In other words, if you mix two transparent solutions and produce a cloudy mixture that eventually settles to form a powdery solid, that is a chemical precipitation. • Don’t mix up chemical precipitation with meteorological precipitation, which is rain or snow. Transparent Cloudy Transparent

26. Examples:

27. Ex #1: Which of the following are examples of physical changes? 1. Melting Butter 4. Crushing Rock 5. Condensation 2. Rusted Car 3. Dissolving Sugar in Tea 6. Burning Wood

28. Ex #2: Which of the following are examples of chemical changes? 1. Cooking an egg 4. Freezing Rain 2. Rotting food 5. Burning a candle 3. Sublimation of Dry Ice 6. Crumpling Paper

29. Where did a chemical change occur? A physical change? Ex #3: You carry out the following steps of an experiment & record your observations. 1. You place a powder in a test tube 2. You heat the test tube. You notice that a colorless gas & a copper-colored liquid are produced. 3. You collect the copper-colored liquid & cool it. It becomes a solid. Chemical Change Physical Change

30. Assignments on Physical and Chemical Changes • Read Textbook pp. 43 to 58, q. 9-15 • Do Workbook pp. 23-26 (energy) • Do Workbook pp. 27-36 (changes)

31. Chapter End Questions • Textbook pages 59 to 61 • Write down the date of the chapter 2 test in your agenda or homework book.