Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: acid, base, catalyst, chemical change, coefficient, conservation of matter, decomposition,
dissolve, double replacement, endothermic, exothermic, indicator, ion...
Chemical Changes
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.
Vocabulary: acid, base, catalyst, chemical change, coefficient, conservation of matter, decomposition,
dissolve, double replacement, endothermic, exothermic, indicator, ion, physical change, product, reactant,
single replacement, subscript, synthesis
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. 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?
yes because the bubbles means gas is expanding which is a
sign of a chemical reaction.
2. Suppose this was done on top of a balance. Do you think the mass would
change as the reaction proceeded?
yes
3. What do you think would happen to the mass if the reaction took place inside a sealed plastic bag?
the mass would stay the same because the gas is being collected
Gizmo Warm-up
A chemical change, (or chemical reaction) occurs when one or more
substances, called reactants, are transformed into different substances, or
products. In the Chemical Changes Gizmo, you will look for evidence of
chemical changes by looking at changes you can see, touch, or smell.
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?
When the Sodium is put inside the water container, there is a chemical reaction,
because gas is created, there is a fizzing sound. Also the sodium dissolves in the water,
but there is not a change of color
, I think there is a chemical reaction, because there was a change of temperature,
evolution of gas and there was a fizzy sound coming from the reaction. In addition, the
PH of the water changed, which means hydrogen ions were released
Activity A: Get the Gizmo ready:
● Click Reset ( ). Check that the reactants are
Observing still Sodium and Water.
chemical changes ● 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? 21
B. Click Play, and wait for the reaction to end. What is the final temperature? 59
C. Was this reaction exothermic or endothermic? exothermic
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?
it shows that water is neutral
B. Click Play, and wait for the reaction to end. What does the indicator show now?
the substance is a a base, after the reaction
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?
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