Unit 4

Question 1

List the reactants and products for the following equation:

1WO3 + 3H2 -> 1W + 3H2O

Answer 1

Reactants- 1WO3 and 3H2

Products- 1W and 3H2O

Question 2

What is meant by “Atoms are conserved in chemical reactions” (Law of Conservation of Mass)?

Answer 2

They are equal on both sides

Question 3

Define physical property

Answer 3

Size, shape, color (something that you can see)

Question 4

Define chemical property

Answer 4

Forms new substances when they break down

Question 5

Classify each as a physical or chemical property:
__ Blue color ___ sour taste
____ hardness ___melting point
__density ___reacts with acid to form h2
__odor
__Flammability

Answer 5

All physical except flammability and reacts with acid to form h2

Question 6

Define physical change and give examples

Answer 6

When something changes size/property

Cutting, melting

Question 7

Define chemical change and give some examples

Answer 7

When a new substance is formed

When water breaks down into hydrogen and oxygen

Question 8

Is dissolving a physical or chemical change?

Answer 8

Physical, it’s a state change

Question 9

Explain how a chemical change occurs when a piece of paper is burned

Answer 9

New product is formed

Question 10

What is the result of a chemical change

Answer 10

A new product

Question 11

Compare/contrast endo and exo

Answer 11

Endo-releases cold- required to get reaction started

Exo- releases warm- given off when reaction occurs

Question 12

Identify the examples below as endothermic or exothermic:

• instant cold pack
• Drain cleaner
• meal, ready to eat (MRE)

Answer 12

Instant cold pack: endo
Drain cleaner: exo
MRE: exo