Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lesson 11 Matter, Energy, and Changes 1. Forms of Energy a. b. c. Energy is the ability to do work. There are two general types of energy. Kinetic energy is the energy of motion: i.Kinetic energy is energy that moving objects possess by virtue of their motion. ii. The amount of energy in an object, depends on the mass and the velocity of the object, according to the following formula: KE = ½(mass)*(velocity)2 iii. KE is measured in units of kg*m2/s2 iv. This formula is used extensively in physics b. Potential Energy is stored energy. i. Potential Energy is energy that an object possesses because of its position – it is also known as stored energy. ii. This energy corresponds to the amount of energy required to keep the object in that position. iii. Objects in an elevated position possess potential energy – the higher the object the more potential energy is possesses. iv. Position does not only include height: 1. A spring in a watch can possess potential energy, because of the fact that is is coiled into a specific “position”. 2. Chemicals can possess potential energy because of the position of the elements which make them up and the ways in which they are bonded. 3. Example: ATP c. Changes in Energy i. Energy can change from one type to another - such as kinetic to potential. ii. Example: Swinging Person at the top of each trip forward or back, the person momentarily is at rest and possesses potential energy iii. Endothermic: changes which absorb heat when they occur – melting, boiling, and cooking are examples iv. Exothermic: reactions which give off heat when they occur – condensation, freezing, and a chemical heat pack are examples. v. Keep in mind that the change we are looking at is the internal change in energy. 1. For some of these, it is easy to predict- for example a fire is exothermic because you can feel the heat coming out of the reaction. 2. For others, it is more difficult. Consider the following: a. chemical ice pack: gets cold because it absorbs the heat from around it – therefore it is endothermic. b. cooking a chicken – the food gets warm inside and the heat going in causes chemical reactions – therefore it is endothermic. c. Water freezing – the water gets cooler, giving off heat energy to the air around it- therefore it is exothermic. II. Relating Mass and Energy: a. Mass is a form of energy i. Einstein discovered the relationship between mass and energy: 1. Formula: E = mc² 2. Explanation: E = energy m = mass c = speed of light 3. In other words, a very large amount of energy is contained in a very small amount of matter b. Energy cannot be created or destroyed i. Energy can be transformed from one kind to another. ii. Energy can be transferred between objects. iii. Law of Conservation of Energy: energy can neither be created or destroyed; it can only change form. iv. The total amount of energy in the universe remains constant. v. The total amount of energy in a closed system also remains constant. vi. Law of Conservation of Mass: mass cannot be gained or lost in a normal chemical reaction. vii. Our are of study will be normal chemical reactions, so this law is VERY IMPORTANT! Demonstration of the Law of Conservation of Mass III. Matter Changes a. Physical Changes do not affect chemical compostion i. Physical changes are changes that only affect physical properties. ii. Chemical properties are unaffected. iii. Some examples of physical changes: 1. Breaking something into smaller pieces. 2. Mixing things together that do not react. (such as sand and iron filings) 3. State Changes b. Chemical changes alter chemical composition i. Chemical change: a change where one or more new substances are produced. ii. The total number of atoms does not change. iii. Signs of a chemical reaction: (although not proof) 1. Bubbles 2. Formation of a precipitate 3. Heat 4. Light 5. Color change ii. All chemical changes involve some transfer of energy. iii. Examples of chemical changes: 1. Burning 2. Digestion 3. Acid/Base reactions 4. Building of glucose molecules by photosynthesis DEMONSTRATIONS Endothermic, Exothermic, Physical, and Chemical Reactions Demonstrations: Acid and Metal Ammonium Nitrate and water Salt water separation Common Pitfalls Students often confuse chemical and physical changes, because they think that they are mutually exclusive, ie. Not able to be present at the same time. Often times, a chemical change, such as burning, is accompanied by physical changes, such as color change. Keep this in mind as you think about what happens during these two types of changes! Questions: 1. Compare and contrast the two different types of energy. 2. What is the equation, and the meaning of the variables in it, that relates matter to energy? 3. Define the law of conservation of mass, and the law of conservation of energy. 4. Draw a diagram relating the three common states of matter, and the names for the changes among them. 5. List the five signs that indicate a chemical reaction may have taken place. 6. Indicate which type of change each of the following indicates, both physical/chemical and endothermic/exothermic. Item Cooking a chicken A campfire Breaking a ruler Boiling water Using a chemical ice pack Painting a house Dew condensing on grass Firecracker exploding Photosynthesis Physical/Chemical or both Endorthermic or Exothermic xxx xxx