Chemical reactions

What are the observations that usually signify a chemical change?

Color change, temperature change, gas production, pH change, and production of a precipitate.

What does every chemical change involve?

The production of a new substance.

What is a precipitate?

A solid that forms from the reaction of two liquids; represented by 'S' in a chemical equation.

What does the law of conservation of mass state?

Mass is neither created nor destroyed during a chemical reaction.

Why do chemists use a chemical equation?

To represent the chemical reaction taking place and to show that the law of conservation of mass is being met.

List two ways you could 'read' the arrow in a chemical equation.

Yields or produces.

What is a chemical equation?

A symbolic representation of a chemical reaction, showing the reactants and products.

What does a skeleton equation NOT show?

The balanced reaction – the total amount of atoms present.

In an equation, what does (s), (l), (g), and (aq) stand for?

(s) means solid, (l) means liquid, (g) means gas, (aq) means aqueous.

What are coefficients?

Numbers placed in front of compounds or elements to show the law of conservation of mass is being met by balancing the reaction.

What is a balanced equation?

An equation in which each side has the same number of atoms.

If a coefficient isn’t written, what is understood to be there?

1.

List the five general types of reactions.

Single replacement, double replacement, synthesis, decomposition, combustion.

What is a synthesis reaction?

A reaction where two single elements combine to form one product.

In all synthesis reactions, what is the product?

A compound.

What is a decomposition reaction?

A reaction where 1 compound decomposes into its elements.

Decomposition reactions involve how many reactants and how many products?

2 reactants and 1 product.

What is a single-replacement reaction?

A reaction where a single element replaces a like element in a compound reactant.

How can you identify a single-replacement reaction?

The reactants will always be a single element and a compound.

What happens to the activity of the halogens as you go down the group?

Reactivity decreases.

What is a double-replacement reaction?

A reaction where two ionic compounds switch partners to create two new compounds.

What is a combustion reaction?

A reaction that starts with a hydrocarbon and oxygen, producing water and carbon dioxide.

What is a hydrocarbon?

A compound that consists of only carbon and hydrogen.

The combustion of a hydrocarbon produces what?

Carbon dioxide and water.

What does a balanced chemical equation allow you to determine?

The number of atoms of each element contained in the reaction.

What does 'aq' mean?

The substance has been dissolved in water.