lesson 9- chemical reactions and balancing equations

Question 1

characteristics of chemical reactions

Answer 1

1. all involve the production of new substances with own characteristic properties
2. all involve the flow of energy
3. when substances are formed sometimes changes of state are noticeable
4. all are consistent with law of conservation of mass

Question 2

flow of energy

Answer 2

when ALL chemical reactions involve transfer of energy

Question 3

combustion

Answer 3

substance reacts with oxygen to produce heat

Question 4

cellular respiration

Answer 4

process which living things convert food into energy

Question 5

exothermic

Answer 5

energy is released, or exits.

Question 6

endothermic

Answer 6

energy is absorbed or enters.

Question 7

cold pack

Answer 7

substances react to energy absorbed from the surroundings
(e.g. an injured person)

Question 8

photosynthesis

Answer 8

plants absorb energy from the sun to produce food

Question 9

change of state

Answer 9

depending on reactants and environment of a reaction.

Question 10

what makes a change of state occur?

Answer 10

temperature and pressure may change states of a reactants

Question 11

Law of conservation of Mass

Answer 11

total mass of a system never changes.

Question 12

total mass of all reactants equals what

Answer 12

total mass of the products

Question 13

balancing chemical equations

Answer 13

coefficients used so there are equal numbers of atoms of each element on the reactant and product.

Question 14

balance: Ca(s) + Kl(aq) = k(s) +CaCl2(aq)

Answer 14

Ca(s) + 2KCL(aq) = 2K(s) + CaCl2(aq)

Question 15

solid magnesium reacts with hydrochloric acid to produce hydrogen and aqueous magnesium chloride

Answer 15

Mg(s) + 2HCL(aq) = H2(g) + MgCl2 (aq)