Answer:1. physical property.
2. chemical property.
3. chemical property.
4. physical property.
Explanation:
Physical property is defined as the property which can be measured and whose value describes the state of physical system. For Example: State, density etc.
Chemical property is defined as the property of a substance which is observed during a reaction where the chemical composition identity of the substance gets changed.
1. Hydrogen is a colorless, tasteless, and odorless gas : physical property as there is no change in chemical composition
2. Hydrogen is very combustible in the presence of oxygen :chemical property as there is a change in chemical composition
3. Hydrogen is very reactive with most elements :chemical property as there is a change in chemical composition
4. Hydrogen is the least dense of all elements : physical property as there is no change in chemical composition
