Scars can react differently to the sun depending on their maturity and the individual's skin type. New scars, especially those that are still healing, are more sensitive to the sun and can become darker and more noticeable when exposed to UV rays. Older scars may also darken or become more prominent when exposed to the sun, as the skin surrounding the scar may tan while the scar tissue does not. It is important to protect scars from sun exposure by using sunscreen or covering them with clothing to prevent further darkening or damage. **

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. **

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. **

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. **

After getting a new tattoo, it is important to keep it protected from the sun. The sun's UV rays can cause the tattoo to fade and damage the skin, leading to potential complications like blistering or scarring. It is recommended to keep the tattoo covered with clothing or sunscreen with a high SPF level when exposed to the sun to preserve its vibrancy and prevent any adverse reactions. **

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. **