Ch 8

Question 1

In a physical change

Answer 1

• The identity and composition of the substance do not change
• The state can change or the material can be torn into smaller pieces

Question 2

In a chemical reaction

Answer 2

• A chemical change produces one or more new substances
• There is a change in the composition of one or more substances
• Old bonds are broken and new bonds are formed
• Atoms in the reactants are rearranged to form one or more different substances

Question 3

Changes that can be seen are evidence of

Answer 3

of a chemical reaction.

Question 4

Chemists use a shorthand approach when writing the specifics of a chemical reaction

Answer 4

This approach is called the chemical equation

Reactants —–> Products

Question 5

A chemical equation

Answer 5

Gives the chemical formulas of the reactants on the left of an arrow and the products on the right

Question 6

Symbols used in chemical

equations show

Answer 6

• The states of the reactants
• The states of the products
• The reaction conditions

Question 7

In a balanced chemical reaction

Answer 7

-Atoms are not gained or lost

-The number of reactant
atoms are equal to the number of product atoms

Question 8

Chemical equations summary

Answer 8

• symbolic descriptions of chemical reactions.
• Two parts to an equation: reactants and products

A Chemical Equation must also be balanced

Question 9

Coefficient

Answer 9

numbers in front of the chemical formulas; give ratio of reactants and products.

• CONVERSION FACTORS!!!
• Changing these changes the number of molecules

Question 10

Formula subscript

Answer 10

• number in the middle of chemical formulas; give the number of each kind of atoms in individual molecules
• Changing these changes the identity of the compound

Question 11

Chemical Equations must be balanced

Answer 11

There must be equal numbers of atoms of each element on both sides of the equation (both sides of the arrow)

Question 12

Steps to balancing out a chemical equation

Answer 12

1. Write the correct symbols and formulas for all of the reactants and products.
2. Count the number of each type of atom on BOTH sides of the equation.
3. Insert coefficients (numbers to the left of the compound formulas) until there are the equal numbers of each kind of atom on both sides of the equation.

Question 13

Hints on Balancing Equations

Answer 13

1. When there is no coefficient written, the coefficient is assumed to be 1
2. To balance the equation insert COEFFICIENTS.
3. NEVER alter the subscripts because that would change the chemical formula which would change the identity and properties of the substance.
4. Start with atoms that only show up in only one compound on each side of the equation arrow.
5. The only way to learn to balance equations is through practice

Question 14

Chemical reactions can be classified as

Answer 14

• Combination reactions
• Decomposition reactions
• Single replacement reactions

-Double replacement
reactions

-Combustion reactions

Question 15

In a combination reaction

Answer 15

• Two or more elements form one product

- Or simple compounds combine to form one product

Question 16

In a decomposition reaction

Answer 16

One substance splits into two or more simpler substances

Question 17

In a single replacement reaction

Answer 17

One element takes the place of a different element in a reacting compound

Question 18

In a double replacement

Answer 18

Two elements in the reactants exchange places

Question 19

In a combustion reaction

Answer 19

A compound such as carbon reacts with oxygen