Water h2o is made up of different elements hydrogen and oxygen is this type of combination of mixture or a pure substance

The given compound (water) is a pure substance

Explanation:

A pure substance is defined as the substance which is formed by same or different type of atoms which are chemically combined in a fixed ratio by mass.

Compounds and elements are considered as pure substances

A mixture is defined as the substance which is made by mixing two or more substances in any ratio.  They can be separated by physical means.

Water is formed by the combination of hydrogen and oxygen elements in z fixed ratio of 1 : 8 by mass. Therefore, it is considered as a compound.

Hence, the given compound (water) is a pure substance

ca has a crystalline lattice with positive ions (since it is a metal, metals are positively charged) and electrons flow freely in its structure since the ca atoms have a large nuclear radius so the electrons are not tightly held, therefore the electrons can flow freely since they are not being highly attracted by the nucleus. moreover, one of the properties of metals are that they are conductors of electricity, thus proving ca is the element.