A method of transitioning a polymerization reaction making an ethylene/alpha-olefin copolymer with a same chromium-based catalyst system in a single gas-phase polymerization reactor operating at a first reactor bed temperature (RBT1), a first average polymer residence time (avgPRT1), and a first ethylene partial pressure (C2P1) and receiving an ethylene (C2) feed, a comonomer (Cx) feed, a hydrogen (H 2 ) feed, and, optionally, an oxygen (O 2 ) feed, wherein the feeds are characterized by a first H2/C2 gas molar ratio (H2/C2-1), a comonomer/ethylene gas molar ratio ("Cx/C2"), and a first O2/C2 gas volume ratio ("[O2/C2]1", vol/vol expressed in parts per million by volume (ppmv)); the method comprising: (a) making, in the reactor under first polymerization conditions comprising H2/C2-1, Cx/C2, [O2/C2]1, RBT1, and C2P1, a first ethylene/alpha-olefin copolymer having a first melt storage modulus G' (G"=3,000 Pa) value (MSM1) measured according to the Melt Storage Modulus Test Method, a first Composition Distribution Breadth Index value (CDBI1), a first density (p1), and a first flow index ("(I 21 )1"); followed by (b1), (b2), or (b3): (b1) raising or lowering the reactor bed temperature in the gas-phase polymerization reactor from RBT1 to a second reactor bed temperature (RBT2), which is from 1 to 10 degrees Celsius (° C.) higher or lower than RBT1; or (b2) decreasing or increasing, respectively, the H2/C2 gas molar ratio of the hydrogen and ethylene feeds from H2/C2-1 to a second H2/C2 gas molar ratio (H2/C2-2), which is from 0.01 to 0.20 lower or higher than H2/C2-1, in such a way that the comonomer/ethylene gas molar ratio value Cx/C2 is unchanged; or (b3) decreasing or increasing the flow index of the ethylene/alpha-olefin copolymer from (I 21 )1 to a second flow index ("(I 21 )2"), which is from 0.1 to 5 grams per 10 minutes (g/10 min.) lower or higher than (I 21 )1; wherein steps (a) and any one of (b1) to (b3) are conducted at the same comonomer/ethylene gas molar ratio value Cx/C2; thereby substantially changing the melt storage modulus G' (G"=3,000 Pa) of the ethylene/alpha-olefin copolymer without using a different alpha-olefin in the Cx feed and without substantially changing its density; wherein a substantial change in melt storage modulus G' (G"=3,000 Pa) means the MSM2 of the second ethylene/alpha-olefin copolymer is higher or lower than the MSM1 of the first ethylene/alpha-olefin copolymer by at least 10.0%; wherein without substantially changing density of the ethylene/alpha-olefin copolymer means ρ2 is within ±0.004 g/cm 3 ; wherein the density is measured in accordance with ASTM D792-13, Method B; flow index (I 21 ) is measured in accordance with ASTM D1238-13 (190° C, 21.6 kg); and melt storage modulus is measured in accordance with the description. wherein a substantial change in melt storage modulus G' (G"=3,000 Pa) means the MSM2 of the second ethylene/alpha-olefin copolymer is higher or lower than the MSM1 of the first ethylene/alpha-olefin copolymer by at least 10.0%; wherein without substantially changing density of the ethylene/alpha-olefin copolymer means ρ2 is within ±0.004 g/cm 3 ; wherein the density is measured in accordance with ASTM D792-13, Method B; flow index (I 21 ) is measured in accordance with ASTM D1238-13 (190° C, 21.6 kg); and melt storage modulus is measured in accordance with the description. <EOS>