Like the days of the month, the chemical elements can be arranged in a way that shows a repeating, or PERIODIC pattern. DRY ERASE EXERCISE Patterns: atomic # increases as you move left to right Groups share same # of valence electron Energy levels increase as you move down a group
Remember: a substance is an element or compound. New elements are not FORMED in reactions. ***The (g) is for gas and (l) is for liquid coefficients tell how many molecules of each substance are involved in each reaction - no coefficient means there is just ONE molecule
C 6 H 12 O 6 + O 2 = CO 2 + H 2 O is the reaction in your body's cells that turn sugar and oxygen into usable energy (ATP), with CO2 and water as waste products ***reaction is reversed in plants (sugars are created from water and CO2 with sunlight's energy) OFTEN A TRIAL AND ERROR PROCESS TO GET THINGS BALANCED
A catalyst is a substance that speeds up a reaction without being used up itself . Here is an example of a reaction with a catalyst. Hydrogen peroxide decomposes (falls apart) to form water and oxygen gas: hydrogen peroxide —> water + oxygen This reaction only occurs very slowly unless we add the compound manganese oxide that acts as a catalyst for this reaction. When the catalyst is added the reaction speeds up greatly but the manganese oxide never runs out. How does a catalyst work? 1) A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting. 2) A catalyst lowers the activation energy (the minimum amount of energy needed for a reaction to take place). This means that the particles can react with less energy than they needed before the catalyst was added. If we lower the amount of energy needed for particles to react, then more particles can react .
C 3 H 8 = propane
Chemical Reactions Basic Chemistry Heartlife Physical Science
Example: Balance the equation that takes place when sodium hydroxide reacts with sulfuric acid to form sodium sulfate and water.
Chemical Reactions Check to be sure you have the same number of atoms of each element on both sides of the equation. Step 4 Try coefficients that will balance the equation. - Start with elements that appear only once on each side of the equation. - Never change the subscripts in a chemical formula. Step 3 Count the number of atoms of each element on each side of the equation. (use a table to keep track) Step 2 Identify reactants & products and write their chemical formulas on the appropriate sides of the equation. Step 1