Gizmos Student Exploration: Chemical Changes.

Student Exploration: Chemical Changes 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, as shown in the image, there are bubbles, therefore gas is being released, which are characteristics of a chemical change. 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? Then, the mass would not change, because the gases being released in the reaction are 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? Student Exploration: Chemical Changes 2018 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. 2.Do you think a chemical reaction has taken place? Explain. 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: 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? 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 indicator shows that the substance is a base, after the reaction