Physical and Chemical Properties and Changes Gizmo Lab Student Exploration:
Physical and Chemical Properties and Changes

Prelab (Do these BEFORE the lab.)

A chemical change, (or chemical reaction) occurs when one or more substances, called reactants, are transformed into different substances, or products. In the Lab, you will look for evidence of chemical changes by looking at changes you can see, touch, or smell.

1. Name 3 examples of each type of property
Physical Property Chemical Property

2. Name 3 example of each type of change.
Physical Changes Chemical Changes

3. From the earliest of times, humans observed that mixing substances sometimes resulted in changes to the substances. Some changes involved physical changes, such as altering the shape of a substance or its state. Other changes involved a chemical transformation of the original substances and the release of heat and light as fire. List 3 changes do you see in everyday life that results in heat being released or absorbed.

4. A student mixes baking soda and vinegar in a glass. The results are shown at left. Do you think any new substances are being created in this mixture? If so, how do you know?

3. Hypothesize Look at the substances listed in the material list. Make educated guesses about what physical and chemical changes might occur when some of them are mixed. Write your hypothesis as an if-then statement such as “if I mix water and chalk powder, then the chalk will dissolve by not chemical change will take place.”
Physical change hypothesis: If then

Chemical change hypothesis: If then

Gizmo Warm-up
To begin, check that Reactant 1 is Sodium and Reactant 2 is Water. Sodium is a metal so soft you can cut it with a knife.

1. Click Play ( ). What do you observe?

2. Do you think a chemical reaction has taken place? Explain.

Activity A:

Observing chemical changes Get the Gizmo ready:
• Click Reset ( ). Check that the reactants are still Sodium and Water.
• Turn on the Label reactants checkbox.

Introduction: It is important to distinguish chemical changes, in which new substances are formed, from physical changes, which do not create new substances. In this activity, you will look at many kinds of evidence that chemists use to see if a chemical change has taken place.

Question: What kinds of evidence indicate a chemical change has taken place?

1. Observe: Some chemical reactions release heat, and others absorb heat. In an exothermic reaction, heat is released and the temperature of the system rises. In an endothermic reaction, heat is absorbed and the temperature of the system decreases.

In the Gizmo, drag the Thermometer into the flask of water.

A. What is the starting temperature?

B. Click Play, and wait for the reaction to end. What is the final temperature?

C. Was this reaction exothermic or endothermic?

2. Observe: Two families of chemicals are acids and bases. Acids and bases can be detected by an indicator, which is a substance that changes color in the presence of an acid or a base. Phenol red is an indicator that is yellow in an acid, orange in a neutral solution, and pink in a base.

A. Click Reset. Drag the Phenol red next to the flask of water. What does the indicator show?

B. Click Play, and wait for the reaction to end. What does the indicator show now?
3. Observe: Click Reset. Select the Gas collection setup. Chemists use this apparatus to collect any gases produced in the reaction. From the reaction flask, gases travel through a long tube and into a cylinder of water. As gases bubble into the cylinder, the water is displaced (removed) until the cylinder is filled with gas.

Click Play and observe the cylinder. Was any gas produced in the reaction? How do you know?

4. Analyze: One way to test what kind of gas is in the cylinder is to use a splint test. A glowing splint is a wooden stick that has been lit on fire and then blown out, resulting in a glowing, red-hot tip. A burning splint is a splint that has a burning tip.

The table shows how a splint reacts to some common gases:

Gas Carbon dioxide (CO2)
or ammonia (NH3) Oxygen (O2) Hydrogen (H2)
Glowing splint Goes out Ignites (burns) Does not ignite
Burning splint Goes out Continues to burn Small explosion and “pop” sound

A. Drag the glowing splint next to the cylinder, and observe. What do you see?

B. Click Reset and click Play, and then bring the burning splint to the cylinder. What happens now?

C. Based on the table above, what gas do you think was produced in this reaction?