One of the starting substances (ingredients) that is involved in a chemical reaction

Explanation:

In a chemical reaction, the starting substances are known as reactants and the ending substances are known as products.

When we write a chemical reaction equation then substances present on the left hand side of arrow are the reactants. Whereas the substances present on the right hand side of arrow are the products.

For example

Here, both A and B are the reactants whereas AB is the product.

Thus, we can conclude that one of the starting substances (ingredients) that is involved in a chemical reaction are reactants.

it is important to conserve water because there is very limited amount of freshwater here on earth and if we are not smart about how we use it we will only be runnning out of our supply faster than neccessarry.

they are made of gases.

they have a spherical shape.

they make energy through fusion.