HOW DOES ONE STUDY FOR A LAB? Practice with the tools, e.g. thermometer, scales, weighing tray, stopwatch, calculators Practice making graphs, especially line graphs (x: time, y: temperature), using data tables Memorize the definitions of key science words Review lab reports (Googledocs) Use other sources for quizzing, e.g. BrainPop, aboutChemistry.com Make own quiz/test Have a peer/parent quiz you on definitions/method
KEY WORDS: CHEMICAL CHANGE Precipitate (product Temperature change with different during reaction properties) • Exothermic lab • Magnesium Carbonate lab • Endothermic lab Gas released (newColor Change substance)• Blue Bottle lab • Law of Conservation of Mass lab Chemical • Dissolving Berocca tablet change
chemical change A chemical reaction is a chemical change which forms new substances; the starting materials (reactants) are different from the product When a chemical change takes place there is the change of temperatures where there might be loss of heat but in most chemical change reactions heat or energy is produced. Another characteristic of a chemical change is the change in color. For example when an iron nail comes into contact with water, the nail begins to rust and its color change from silver to reddish brown meaning that chemical change has taken place. The production of gases and solids is also another characteristic of a chemical change. The gases produced appear in the form of bubbles as a result of the reaction. A solid maybe formed and it separates itself from the solution after the reaction.
Endothermic reaction An endothermic reaction is any chemical reaction that absorbs heat from its environment. It is a reaction that requires energy to proceed. The intake of energy may be observed as a decrease in temperature as the reaction proceeds. Once the reaction is complete, the temperature of the mixture will return to room temperature. Examples 1. reacting acetic acid with sodium carbonate 2. photosynthesis (chlorophyll is used to react carbon dioxide plus water plus energy to make glucose and oxygen)
Exothermic reaction Many chemical reactions release energy in the form of heat, light, or sound. These are exothermic reactions. Exothermic chemical reactions produce heat. Examples1. In this reaction vinegar is used to remove the protective coating from steel wool, allowing it to rust. When the iron combines with oxygen, heat is released.
Collecting Data Endothermic ExothermicInitial Temperature °C °CFinal Temperature °C °CTemperature changerate
Law ofConservation of MassCHALLENGE: EXPLAIN WITH EXAMPLE
Law of Conservation of Mass Matter cannot be created nor destroyed, but it can be transformed in shape, state and volume. the mass of substances produced (products) by a chemical reaction is always equal to the mass of the reacting substances (reactants) in a closed system.Example 1.00g carbon + 5.34g sulphur 6.34g carbon disulphide
CHEMICAL CHANGE PHYSICAL CHANGE In a chemical change where there is a A physical change in a substance doesntchemical reaction, a new substance is change what the substance is.formed and energy is either given off orabsorbed.If a piece of paper is burned, it is broken up For example, if a piece of paper is cut up intointo different substances that are not paper. small pieces it still is paper. This would be a physical change in the shape and size of the paper.Chemical changes cannot be reversed with Physical changes can be reversed.the substance changed back withoutextraordinary means, if at all.If one made a recipe for a cake with flour, If one decided to mix sugar/salt into waterwater, sugar and other ingredients and to make sugar/salty water, this would be abaked them together, it would take physical change as the water could be leftextraordinary means to separate the various out to evaporate and the sugar/salt crystalsingredients out to their original form. would remain. Note: remember salt is sodium chloride (NaCl)
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