chemistry 1

Lab 4: Physical and Chemical Properties and Reactions

Lab Materials:

Tide TM

powder detergent

Vinegar

Iodine

Cream of Tartar

Lemon Juice

Baking Powder

Baking Soda

Cornstarch

Q-tips

Rubbing alcohol

Wax paper

Sharpies (to label wax paper)

Plastic spoons

Medicine droppers

Small or large plastic cups

Water

Physical and Chemical Properties and Reactions

Name: _____________________________ Date: _________

Introduction

Physical properties are characteristics a sample displays without changing its composition. For

instance, how something looks, tastes, smells, and even its density are all examples of physical

properties. A chemical property is a characteristic a substance displays only when it changes its

composition. For instance, the gasoline you burn in your car is an example of a chemical property,

in this case the gasoline’s flammability.

When matter changes form as it frequently does, two changes could take place. If a physical

change takes place, the matter does not change its composition. Phase changes are examples of

physical changes. If you think about leaving an ice cube on the kitchen counter, after a while the

ice will begin to melt to leave a nice puddle. Even though the ice cube and the puddle of water

look very different, they are still composed of water molecules. If a chemical change (or chemical

reaction) were to take place, then the matter does change its composition. For this, think of a

campfire. Before you started the fire, you had pieces of wood, but after the fire went out, all you

are left with are ashes. In this case, we have a chemical change. In today’s lab, you will complete

exercises that help you gain a better understanding of physical and chemical properties and

changes.

Directions: 1. For part A, identify each as a chemical (C) or physical (P) property. For part B, classify each

as either a physical (P) or chemical (C) change.

Part A:

1. The smell of spearmint gum

2. Iron’s ability to react with oxygen to form rust

3. Mercury being a liquid at room temperature

4. Baking flour’s texture

5. An emerald’s green color

6. Chlorine gas liquefies at –35oC under normal pressure

7. Hydrogen burns in chlorine gas

Part B:

1. Fingernail polish remover evaporating from a cotton swab

2. Salt dissolving in a cup of water

3. A car rusting

4. A mirror shattering

5. A granite statue being “eaten” by acid rain over several years

6. A strong acid reacting with a strong base to form water and a salt

7. Burning of sulfur

2. Complete the following table.

3. Soak a Q-tip in rubbing alcohol (wet, but not dripping). Drag it across a countertop to make a foot long streak.

1 You might have to wait several minutes to answer the following questions—it

depends on how wet your Q-tip was.

a. What happens to the streak?

b. Does this occur instantly, continuously or in stages?

c. How long does it take?

d. Are you observing a chemical or physical change?

Sample

Physical

State

(s, l, g)

Appearance

(color, odor, texture…)

Laundry detergent

Vinegar

Iodine

Cream of tartar

Air

Lemon juice

Baking powder

Baking soda

Cornstarch

4. When completing the table in problem #2, you probably realized that some forms of matter would be difficult to distinguish if they had not been properly labeled, i.e. your description of the

substances’ appearance was very similar. In the next part of this lab, you will learn how you can

distinguish between some of these substances through chemical reactions. To do this, you will

need to mix three liquids with 5 powders. Use a piece of wax paper and medicine dropper(s) to

conduct your experiments. Make sure you watch the pre-lab video for guidance on this part. If

you only have one medicine dropper, make sure to clean it before dispensing another liquid. Use

the table below to record the results of your experiments. 2

5. Using baking soda, vinegar and a small plastic cup, determine if the amount of reagents you use

affect the outcome of your observations. Please explain thoroughly your procedure and your

conclusions.

Baking Soda Baking Powder Cornstarch Detergent Cream of

Tartar

Water

Vinegar

Iodine

6. Baking soda is also known as sodium bicarbonate while vinegar is a solution containing acetic

acid, HC2H3O2. Knowing this information, complete the following.

a. Write the chemical formula for sodium bicarbonate. Note: bicarbonate is a polyatomic ion,

HCO3 -1

.

b. Write a balanced chemical equation for the reaction of baking soda and acetic acid. The products of this reaction are carbon dioxide gas, water, and NaC2H3O2.

References: 1 From Dr. George Whitwell, Associate Professor of Chemistry at NCWC

2 Kessler, James, & Galvan, Patricia. (2004). Inquiry in Action: Investigating Matter Through Inquiry

2 nd

ed., American Chemical Society.