Achemist mixes oxygen gas and hydrogen gas to form water, which is composed of one oxygen and two hydrogen atoms per molecule. what has occurred? a physical change b chemical change c combustion d precipitation

The formation of water is a chemical change.

Explanation:

Physical change is defined as the change in which change in shape and size takes place. The chemical composition of a substance remains the same. No new substance is formed during this.

For Example: Melting of ice

Chemical change is defined as the change in which change in chemical composition takes place. A new substance is formed in this.

For Example: Formation of water molecule.

The chemical equation for the formation of water molecule follows:

Hence, the formation of water is a chemical change.

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.

it's all four options.