Amber does not react with water because it is a non-reactive substance. It is a fossilized tree resin that is composed of carbon, hydrogen, and oxygen, which do not undergo any chemical reactions with water. Therefore, when amber comes into contact with water, it does not dissolve or undergo any noticeable changes. **

When an acid is added to water, it dissociates into its ions. The hydrogen ions (H+) from the acid react with the water molecules to form hydronium ions (H3O+). This reaction releases heat and is exothermic. The presence of hydronium ions in the solution makes it acidic. **

Velvet is not water-resistant and can be easily damaged by water. When velvet comes into contact with water, it can become discolored, stained, or lose its soft texture. It is important to avoid getting velvet wet and to take special care when cleaning or handling velvet items to prevent damage from water. **

When ammonia is added to water, it forms ammonium hydroxide, which is a weak base. The ammonia molecule (NH3) reacts with a water molecule (H2O) to form ammonium ion (NH4+) and hydroxide ion (OH-). This reaction increases the concentration of hydroxide ions in the solution, making it slightly basic. The reaction is reversible, meaning that ammonium hydroxide can dissociate back into ammonia and water. **

Lithium reacts vigorously with water, producing lithium hydroxide and hydrogen gas. The reaction is exothermic, meaning it releases heat, and can even ignite the hydrogen gas produced. The reaction is also highly exothermic, and the released heat can cause the hydrogen gas to ignite. Overall, the reaction of lithium with water is highly reactive and should be handled with caution. **

Potassium perchlorate is highly soluble in water, and when it dissolves, it dissociates into potassium ions and perchlorate ions. This dissociation results in the solution becoming acidic due to the presence of perchlorate ions. Additionally, potassium perchlorate can react with certain organic compounds in water, potentially leading to combustion or explosive reactions. Overall, the reaction of potassium perchlorate in water can be exothermic and potentially hazardous. **

Sodium hydroxide reacts with water to produce heat and a highly alkaline solution. This reaction is exothermic, meaning it releases heat as it occurs. The resulting solution is known as sodium hydroxide solution or caustic soda, which is a strong base and can cause severe burns if it comes into contact with skin. The reaction between sodium hydroxide and water is highly exothermic and should be carried out with caution. **

Ethene reacts with bromine water by undergoing an addition reaction. The double bond in ethene breaks, and each carbon atom forms a new bond with a bromine atom. This results in the decolorization of the bromine water, changing it from orange to colorless. This reaction is a characteristic test for unsaturation in organic compounds. **