Please  answer all question

1.At 0 degree and 100 degree change of phase takes place. At 0 degreen ice changes to water and is called the melting point  and at 100 degrees water changes to steam which is called the boiling point of water.

2.Solid carbon dioxide directly changes into carbon dioxide gas and does not melt to produce a liquid (like ordinary ice) hence it is called dry ice.Dry ice is used to deep freeze food and to keep ice creams cold

3.On adding small amount of heat water changesits state.

4. Nh4Cl

5. Density= Mass/Volume.