6.2 Answers - 8th Grade Science Workbook

15. How many atoms of oxygen are there on each side of the following chemical equation: 2 Mg+O2 -> 2 MgO

2 Oxygen and 2 Magnesium are on each side.

1. What is a chemical equation?

A chemical equation is a short way to show a chemical reaction using symbols instead of words.

14. When is a chemical equation balanced?

A chemical equation is balanced when the mass and number of each atom is the same on both sides.

8. Circle the letter of each statement that is true about chemical equations.

B, D

17. A number that is placed in front of a chemical formula in a chemical equation is called a ___________.

Coefficient.

16. Circle the letter of each chemical equation that is balanced.

D.

11. What is the principle called the conservation of matter?

It states that during a chemical reaction, matter is not created or destroyed.

18. What does a coefficient tell you?

It tells you how many of each molecule are in a reaction.

20. Write a balanced equation for this reaction: Oxygen reacts with hydrogen to yield water.

O+H2 -> H2O

7c. Label each formula in the chemical equation below as either a reactant or a product.

Product.

5. The substances you have when a chemical reaction is complete are called the ________.

Products.

7a. Label each formula in the chemical equation below as either a reactant or a product.

Reactant.

7b. Label each formula in the chemical equation below as either a reactant or a product.

Reactant.

4. The substances you have at the beginning of a chemical reaction are called the _________.

Reactants.

21. In what three categories can chemical reactions be classified?

Synthesis, decomposition and replacement.

22. Which category of chemical reactions comes from a term that means "to put things together?"

Synthesis.

19. Tell why this chemical equation isn't balanced. H2+O2 -> H2O

The number of Oxygen atoms decreases and the sides do not obey the principle of the conservation of matter.

10. At the end of a chemical reaction, what is the total mass of the reactants compared to the mass of the products?

The total mass of the reactants is the same as that of the products.

2. True or False? Chemical equations use symbols instead of words to summarize chemical reactions.

True.

9. True or False? All the atoms present at the start of a reaction are present at the end.

True.

6. What do you read the arrow in a chemical equation as meaning?

Yields.