Term | Definition |
activation energy | what is needed to start a chemical reaction |
arrow | you read the arrow as "yields in a chemical equation or formula |
characteristics of a chemical reaction | changes in energy or changes in properties color change |
chemical changes | alter the chemical properties of matter; new substances with new properties are formed |
chemical equations | a shorter, easier way to show chemical reactions by using symbols instead of words |
coefficient | a number placed in front of a chemical formula in an equation. Tells how many atoms or molecules of each reactant and product take part in the reaction |
conservation of mass | the amount of matter involved in a chemical reaction does not change.The total mass of the reactants must equal the total mass of the products |
decomposition reaction | a compound breaks down into simpler substances |
endothermic reaction | an observable change in energy that shows a chemical reaction took place; A reaction that takes heat from the solution, absorbs energy, makes it feel cooler |
exothermic reaction | an observable change in energy that shows a chemical reaction took place; a reaction that releases heat; gives off energy, makes it feel warmer; most chemical reactions are this type. |
Physical Changes | alter only the physical properties of matter; no new substances are formed. Can be a change in size, shape or color; change in phase (by increasing or decreasing temperature: solid, liquid, gas) |
Precipitate | Precipitate: a solid that forms from solution during a chemical reaction; observable change that shows a chemical reaction took place |
Products | the materials you have after a chemical reaction; written on the right side of the formula |
Reactants | the materials you have at the beginning of a chemical reaction; written on the left side of the formula |
Replacement Reaction | one part of a compound is displaced by an element or compound from another substance (also called displacement reaction) |
States of Matter (pp. 46-50): | solid, liquid, and gas |
Subscripts | Subscripts: show the number of atoms of an element in a molecule or the ratio of elements in a compound. |
Synthesis Reaction | Synthesis Reaction: two substances combine to form a new compound (also called composition reaction) |