Which cannot be broken down chemically or physically into a simpler substance between sugar, salt, seawater, and copper?

Cu is an element. Elements may not be broken into smaller substances. Sea water is a mixture of materials with H2O being a compound. Sugar and salt are compounds.

Among sugar, salt, seawater, and copper, copper cannot be broken down chemically or physically into a simpler substance. Copper is an element with the symbol Cu and atomic number 29 on the periodic table. It is a metal that exists in its pure form and cannot be further broken down into simpler substances through either chemical or physical means.

The substance that cannot be broken down chemically or physically into simpler substances is copper.

To determine this, we can look at the properties and characteristics of each substance:

1. Sugar (Sucrose): Sugar is a carbohydrate composed of carbon, hydrogen, and oxygen atoms. It can be broken down into simpler substances through chemical processes such as hydrolysis.

2. Salt (Sodium chloride): Salt is a compound made up of sodium (Na) and chloride (Cl) ions. It can be separated into its component ions through physical processes such as dissolving in water or using an electric current (electrolysis).

3. Seawater: Seawater is a mixture of various dissolved salts, minerals, and other substances such as dissolved gases and microorganisms. It can be separated into its components through physical processes like distillation or evaporation.

4. Copper: Copper is an element, meaning it consists of only one type of atom. It cannot be broken down chemically into simpler substances. Additionally, copper is a solid metal and cannot be easily broken down into smaller pieces through physical means.

Therefore, among the given options, copper is the substance that cannot be broken down chemically or physically into a simpler substance.