Ch.2 Outline - Chapter 2 Outline 1 Elements combine to form...

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Chapter 2 Outline 1. Elements combine to form compounds: A property possessed by nearly every element has the ability to combine with other elements to form compounds- although not all combinations appear to be possible. Chemical formulas specify the composition of the substance- use chemical formulas to describe compounds. Single elements are called free symbols. Free elements are just the chemical symbols (ex. Hydrogen- H). Two atoms in a molecule are called diatomic molecules. (ex. H 2 ) A compounds formula is important because it tells what’s in the substance. Hydrates- anything that contains water in fixed ratios. 2. Chemical equations describe what happens in chemical reactions: Left of the arrow = reactants; right = products Numbers in front of the element symbol are called coefficients. Subscripts are the little numbers after the element symbol Balanced equations- each side is equal in atoms and coefficients are in simplest forms. Solid (s), Liquid (l), gas (g) <- letters after the element in parentheses are indicated states. 3. Energy is an important part of chemical change: Energy is something an object has and is able to do work. Kinetic energy- moving energy; potential energy- stored energy can be changed to kinetic energy. Heat is thermal energy. When chemicals have energy – chemical energy Heat and temperature aren’t the same; temperature is how you measure heat. Law of conservation of energy – energy can’t be created or destroyed or changed from one form to another. 4. Molecular compounds contain neutral particles called molecules:
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Molecules- neutral particle containing two or more atoms Brownian motion- when very small particles suspended in liquid collide with atoms they jiggle, which proves the existence of atoms. Atoms are held together by chemical bonds.
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Ch.2 Outline - Chapter 2 Outline 1 Elements combine to form...

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