Question | Answer |
chemical reaction | when substances break apart or combine to form 1 or more new substances |
what happens in a chemical reaction | new substances form when bonds break and new bonds form, the chemical properties of the new substances are different from those of the original substance |
precipiate | solid substance that forms in a solution |
what are signs that a chemical reaction has occurred | production of a gas, production of a precipiate, giving off of energy, color change |
what kind of change is boiling water | physical change |
what must happen in a chemical change | a new substance must with different chemical properties must be made |
when do chemical reactions happen | when chemical bbonds are broken |
chemical bond | force that holds 2 atoms together in a molecue |
what happens to chemical bonds during a chemical reaction | some break, new bonds form to produce a new substance |
hydrogen and chlorine react to produce hydrogen chloride, what bonds are broken and what bonds are formed during this reaction | bond between he hydrogen atoms break and the bond between the chlorine atoms break, new bonds between hydrogen and chlorine atoms form |
chemical formula | shows which elements are found in a substance, also, it shows how many atoms of each element are found in a molecule of a substance |
what are 2 things that are shown by a chemical formla | th number of atoms of an element in a formula and which elements those are |
subscript | a number that tells you how many atoms of an element are in a molecule |
what does it mean when there is no subscript in a n element's chemical symbol | there is only 1 of the element |
mono | 1 |
di | 2 |
tri | 3 |
tetra | 4 |
penta | 5 |
hexa | 6 |
hepta | 7 |
octa | 8 |
nona | 9 |
deca | 10 |
what does it mean if the name of a compound contains the name of a metal and a nonmetal | it is an ionic compound |
chemical equation | something that uses chemical symbols and formulas as a short way to show what happens in a chemical reaction |
what does a chemical equation show | atoms are only rearranged in a chemical reaction, no atoms are gained or lost |
reactants | starting materials in a chemical reaction |
products | substances that form during the reaction |
why is it important to check and make sure your chemical formulas are correct | if you use the wrong formula or symbol, then the equation will not describe the right reacton |
law of conservation of mass | states that mass can't be gained or lost during a chemical reaction |
why is the chemical equaton always balanced | the number of reactants and products is always equal |
coefficient | a number placed in front of a chemical formula |
how do you use coefficients to balance an equation | count the number of atoms, add coefficients to the different reactants and products to get the reactants to equal the product |
what can't be changed when balancing a chemical equation | subscripts |
what 4 groups do most reactions fall into | synthesis reaction, decomposition reaction, sigle-displacement reaction, double-displacement reaction |
synthesis reaction | reaction in which 2 or more substances combine to form a new compound |
decomposition reaction | reaction in which a single compound breaks down to form 2 or more simpler substances |
single-displacement reaction | reaction in which one element replaces another element in a compound |
what are the products of a single-displacement reaction | a new compound and a replaced element |
if iron replaces copper in Cu(NO3)2, is it more or less reactive than copper | more |
double-displacement reaction | reaction in which 2 ions from 2 different compounds trade places |
which 2 reaction types are the opposite of each other | synthesis and decomposition |
why can the product of a synthesis reaction never be an element | elements and compounds are being added together, not subtracted |
when 2 clear solutions are poured together and a blue precipiate forms, what type of reaction has taken place and why | double-displacement reaction because 1 of the products is often a precipiate |
what is part of all chemical reactions | chemical energy |
how do you find out if more energy is absorbed or released in the reaction | by comparing the chemical energy of the products to the chemical energy of the reactants |
exothermic reaction | reaction that gves off energy |
what are the ways thatexothermic reactions can realease enegy | light, heat, and electricity |
endothermic reaction | reaction that takes in energy |
what are the ways endothermic reactions can take in energy | light, heat. and electricity |
law of conservation of energy | law that states energy can't be created or destroyed |
kinetic energy | energy of motion |
rate of reaction | how fast reactants break apart and products form |
what must happen to reactant particles for a reaction to occur | they must collide |
activation energy | the smallest amount of nergy that molecules need to react |
for an endothermic reaction, do reactantsor products have more energy | products |
what 4 factorsaffect the rate of a reaction | temperature, surface area, concentration, inhibitors or catalysts |
how do higher temperatures affecta reaction rate | it speeds it up |
what is surface area | the amount of exposed surface of a substance |
what happens if you increase the surface area of solid reactants | it increases the rate of reaction |
what is concentration | the amount of 1 substance dissolve in another |
what doesa high concentration of reactants cause | a faster rate of reaction |
inhibitor | substance that slows down or stops a chemical reaction |
what are preservatives | inhibitors that are added to foods to slow down the growth of bacteria and fungi |
catalyst | a substance that speeds up reaction without being permanently changed |
why is a catalyst not a reaction | it isn't permanently changed |
how does a catalyst work | it lowers the activation energy of a reaction |
what happens to energy when a chemical bond forms | it is realeased |
what happens when a chemical bond is broken | it is gained |
how does chewing your food well speed up the reactions in your digestive system | it partially breaks it down |