What is a physical change and a chemical change

A physical change --> is the change in appearance or form Example --> ice melting.

A chemical change --> is the change in chemical composition. Example --> rust

Additionally, physical changes can be reversible (water melting or freezing), while chemical changes can't. Rust cannot be reversed.

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.

1 a

2 d

3 a

4 c

explanation: