The text of oxygen gas in the laboratory ​

Explanation:in testing for oxygen a glowing splint is used.

the glowing splint is brought in the presence of the test tube containing the gas

the glowing splint rekindles or lights up showing that oxygen is present.

this is a positive test because oxygen supports burning or combustion

chemical properties are the characteristic of matter which can only be observed by changing the chemical identity of a sample like flammability reactivity and toxicity.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.