Explanation

The incorrect statement about non-metals is: Non-metals are solid at room temperature.

Non-metals are typically:

• Non-metal are gases
• Non-metals have low melting and boiling point
• Non-metal are poor conductor of heat and electricity
• Non-metal are dull and soft

Explanation

Stationary waves do not carry energy with them as it is stationary or does not change position.

Stationary waves do not transfer energy from one place to another. 

Explanation

 Conductors

Atoms of metallic elements are characterized by the presence of valence electrons, which are electrons in the outer shell of free-moving atoms. It is these ""free electrons" that allow the metal to conduct electricity.

Explanation

Iron oxide is a chemical compound  of oxygen and iron and is most commonly found in the earth's crust in the

form of hematite (Fe2O3). It also exists in the form of

magnetite (Fe3O4).

Explanation

The salt content in seawater is mainly due to the presence of sodium chloride i.e sodium and chlorine. The abundant element in  seawater is chloride, which accounts for 1.94% of  the total composition. 

 Chloride is followed by 1.08% sodium, 0.04% potassium  and a small amount of iodine.

Explanation

nitrogen 

 Therefore, the majority of the atmosphere  is nitrogen, which accounts for 78%.

Explanation

A piece of steel sinks in water because steel is denser than water. However, a steel ship is a hollow object made of steel and contains a lot of air in it.

Due to presence of a lot of air in it, the average density of the ship becomes less than the density of water. Hence a ship floats in water.

Explanation

The drum of a Photostat machine (also known as a xerox machine) is made of a material called selenium,

That is a photoconductive element.

This means that when exposed to light

It becomes conductive, allowing the machine to transfer the image onto the paper. 

Explanation

The cell is the smallest unit of life

The atom is the smallest and most fundamental unit of matter.

It consists of a nucleus surrounded by electrons.

Explanation

Solder is an alloy of  Lead and tin  

An alloy is a mixture of chemical elements of which at least one is a metal.