What dissolves easily in water (soluble):
* Sugars: Table sugar (sucrose), glucose, fructose, etc.
* Salts: Table salt (sodium chloride), potassium chloride, calcium chloride, etc.
* Acids: Vinegar (acetic acid), lemon juice (citric acid), hydrochloric acid, etc.
* Bases: Sodium hydroxide, potassium hydroxide, ammonia (weak base), etc.
* Many gases: Oxygen, carbon dioxide, nitrogen, etc. (although the amount dissolved is limited).
* Some alcohols: Ethanol (drinking alcohol), methanol, etc.
Things that dissolve poorly in water (insoluble):
* Oils and fats: Olive oil, butter, lard, etc.
* Most plastics: Polyethylene, polypropylene, etc.
* Sand and dirt: These are mostly composed of minerals that don't dissolve easily.
* Metals: Iron, copper, silver, etc. (although some metals can react with water to form soluble compounds).
Factors affecting solubility:
* Temperature: Most solids dissolve better in hot water.
* Pressure: For gases, higher pressure leads to more dissolving.
* The nature of the substance: Some substances have a natural affinity for water (like sugar), while others do not (like oil).
Important Note: "Dissolving" doesn't always mean the substance disappears. It means the substance breaks down into smaller particles that are evenly distributed throughout the water. Sometimes, a chemical reaction occurs when something dissolves in water, creating new substances.
