section 3

Question 1

3.1

in a chemical reaction, energy is either released or gained.
[what are these reactions called?]

Answer 1

endothermic and exothermic reactions

Question 2

3.1

exothermic reactions

Answer 2

energy EXits the system as heat
A+B → C+D + energy [joules]

ex cellular respiration

Question 3

endothermic

Answer 3

energy ENters the reaction
energy[joules] + A+B→C+D

ex photosynthesis

Question 4

biochemical reactions

Answer 4

reactions that take place inside living organisms
cellular respiration and photosynthesis are 2 important examples

Question 5

evidence of chemical reaction

Answer 5

1. new substance formed [product]
2. temperature change
3. formation of gas [bubbles] or a solid [precipitate
4. conservation of mass [mass of reactants = mass of products]

Question 6

6 types of reactions

Answer 6

formation
decomposition
single replacement
double replacement
hydrocarbon combustion
neutralization [fancy double replace.]

Question 7

formation

Answer 7

elements/compounds joined together
A+B→AB

Question 8

decomposition

Answer 8

compounds are separated
AB → A + B

Question 9

single replacement

Answer 9

1 element replaces element in a compound
A + BC →AC + B

remember to pair the metal with nonmetal [negative charge w positive]

Question 10

double replacement

Answer 10

elements from each of the 2 compounds switch
AB + CD → AD + CB

remember; METAL with NONMETAL

Question 11

hydrocarbon combustion

Answer 11

hydrocarbon combines w oxygen; product is ALWAYS CO₂ and H₂O

CₓHₓ + O₂ → CO₂ + H₂O

Question 12

neutralization

Answer 12

acid + base → water + salt

HB + COH → HOH + CB

H₂O = HOH