Select the equations below that represent physical changes. choose one or more: a. 2 h2o(l) → 2 h2(g) + o2(g) b. h2o(l) → h2o(s) c. co2(s) → co2(g) d. h2(g) → 2 h(g)

Physical changes- any change in the physical properties of the substance is a physical change. Generally physical properties include color, state, size , shape, odour, appearance . In any phyical change, no new substance is formed.

Chemical changes- any change in the chemical properties of the substance is a chemical change. Chemical properties changes only when something new is formed during a reaction.

∴ Part A- 2 H2O(l) → 2 H2(g) + O2(g)

In this, H2 and O2 is produced during the reaction which is different from H20. Thus, it is a chemical change.

Part B- H2O(l) → H2O(s)

In this, only the state of water changes from liquid to solid and no new product is formed. Thus, it is a physical change.

Part C-CO2(s) → CO2(g)

In this also, only the state of CO2 changes from solid to gas and no new product is formed. Thus, it is a physical change.

Part D-H2(g) → 2 H(g)

In this reaction, H2 molecule is dissociated into 2 hydrogen atom leading to formation of new products. Thus, it is a chemical change.

Finally, equations that represent physical changes are - B and C

B. H2O(l) → H2O(s)

C. CO2(s) → CO2(g)

explanation:

one negative thing it that it can kill water animals. another negative thing is it can cause the destruction of ecosystem. one way water pollution can be reduced is to conserve energy.