The 2 in front of the formula for water is called a coefficient. To accommodate the two oxygen atoms as reactants, let us assume that we have two water molecules as products: We do this one element at a time, going from one side of the reaction to the other, changing the number of molecules of a substance until all elements have the same number of atoms on each side. What you can do, however, is to change the number of molecules that react or are produced. What can we do? Can we change the subscripts in the formula for water so that it has two oxygen atoms in it? No you cannot change the formulas of individual substances because the chemical formula for a given substance is characteristic of that substance. But if we count the number of oxygen atoms in the reactants and products, we find that there are two oxygen atoms in the reactants but only one oxygen atom in the products.

If we count the number of hydrogen atoms in the reactants and products, we find two hydrogen atoms. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products.

The law of conservation of matter says that matter cannot be created or destroyed. Unfortunately, it is also an incomplete chemical equation. The initial substances are called reactants, and the final substances are called products. This is an example of a chemical equation, which is a concise way of representing a chemical reaction. Remembering that hydrogen and oxygen both exist as diatomic molecules, we can rewrite our chemical change as But substances can also be represented by chemical formulas. Where the + sign means that the two substances interact chemically with each other and the → symbol implies that a chemical reaction takes place. We can represent this chemical change more succinctly as Hydrogen reacts with oxygen to make water For example, one chemical property of hydrogen is that it will react with oxygen to make water.

Identify the parts of a chemical equation.Ī chemical reaction expresses a chemical change.

The Chemical Equation Learning Objectives Because chemical changes are so central, it may be no surprise that chemistry has developed some special ways of presenting them. Indeed, if there were no chemical changes, chemistry as such would not exist! Chemical changes are a fundamental part of chemistry. Although the solid rocket boosters each have a significantly lower mass than the liquid oxygen and liquid hydrogen tanks, they provide over 80% of the lift needed to put the shuttle into orbit-all because of chemical reactions.Ĭhemistry is largely about chemical changes. The chemical reaction between these substances produces aluminum oxide, water, nitrogen gas, and hydrogen chloride. Then there are the two solid rocket boosters, which use a solid fuel mixture that contains mainly ammonium perchlorate and powdered aluminum. The three main engines are powered by reacting liquid hydrogen with liquid oxygen to generate water. The rockets that lift the orbiter are of two different types.

The space shuttle-and any other rocket-based system-uses chemical reactions to propel itself into space and maneuver itself when it gets into orbit.

Chemical activity series