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Chapter #5
Chemical Reactions and Quantities
| Question | Answer |
|---|---|
| A _________ ________ happens when the appearance of a substance is altered, but not its composition. It changes states, but does not change into a new substance. | physical change |
| A ________ _________ happens when reacting substances change into new substances that have different formulas and different properties. | chemical change |
| Is this a physical or chemical change? CL2(g)->Cl2(l) | Physical. It simply turned from a gas to a liquid (changed states), but the chemical composition was not altered. |
| Is this a physical or chemical change? PbO2(s)->Pb(s)+O2(g) | A chemical change. The product has a different chemical formula than the reactant. (more specifically, it is a decomposition reaction) |
| When a chemical equation is ________, the equation shows the same number of atoms for each element on BOTH sides of the equation. | balanced |
| When we see the subscript (aq), we know that the element or compound was: | dissolved in water |
| When we see a triangle symbol over the reaction arrow in a formula, we know it was a _________ reaction. | thermal (the reactants are heated) |
| We use coefficients to balance equations, but the ________ in the formulas are NEVER changed. | subscripts |
| The Law of Conservation of Mass states that mass is neither _________ nor _________ in any ordinary chemical reaction. | created / destroyed (in other words, the mass of the substance produced (product) by the chemical reaction is always equal to the mass of the of the reactants.) |
| What are the coefficients in a balanced chemical equation? | Coefficients indicate the number of molecules present of that particular reactant or product. |
| In an oxidation-reduction reaction, the oxidation half of the reaction is when a reactant ________ electrons, meaning it gets more _________. | loses / positive |
| In an oxidation-reduction reaction, the reduction half of the reaction is when a reactant ________ electrons, meaning it gets more _________. | gains / negative |
| The reactant that RECEIVES the electrons given away by the other reactant is the ___________ __________. | oxidizing reactant |
| The reactant that DONATES the electrons to the other reactant is the _______ _________. | reducing reactant. |
Created by:
taranorwood
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