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Temperature’s Effect on the Rate of a Reaction

MATERIALS:

• 4 glasses or clear plastic cups (same size)• Pen or pencil• Paper• 3 effervescent (Alka-Seltzer®) tablets and

water or 4 antacid tablets and clear soda• Ice• Water—room temp and hot tap• Ruler or cardboard or cardstock strip

(something long & flat)

INSTRUCTIONS:Note: If you are using clear soda, it should be microwaved for 60 seconds in a microwave-safe mug. Exact temperature is not important, but each temperature should be noticeably different.

Step 1. Line 3 glasses up in a row on a piece of paper. Use a pen or pencil to mark on the paper in front of each cup “Cold”, “Room Temperature”, and “Hot”.

Step 2. Fill the “Room Temperature” glass 3---4 full of water and wait until it reaches

room temperature.

Step 3. If you do not have a ruler, then cut a piece of cardboard or cardstock into a 1–2-inch-wide strip that is a little longer than the 3 cups lined up.

Step 4. When the room-temperature water is ready, prepare the hot and cold water. Place a few ice cubes in the extra glass and fill it with water. Let it get good and cold and then pour the cold water only into the glass labeled “Cold.” Make sure you remove the ice cubes. Fill the glass labeled “Hot” with hot water from the tap. All 3 glasses should contain the same amount of water.

VOCABULARY:Rate of Reaction—how fast a reaction takes place.

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THE SCIENCE BEHIND IT:An antacid tablet contains a dry acid and a dry base and when you place it in water a chemical reaction takes place between the acid and the base. 1 neutralizes the other. Your stomach is acidic, so sometimes when people have an upset stomach, they take an antacid because it neutralizes the acid. When you add heat to a chemical reaction, you are adding energy and when you add energy, the molecules start to move faster. You should have noticed that the rate of the reaction in the room-temperature water was faster (more fizzing) than the cold water and the rate of the reaction was faster in hot water than it was in the room-temperature water. Generally, this is the case for most reactions up until a certain temperature.

INSTRUCTIONS (CONTINUED):STEP 5. Rest the ruler or strip of cardboard across the top of the glasses and place a

tablet so that is over the center of each glass. Flip the strip so all 3 tablets fall into their respective glasses at the same time. Observe the reaction. Which tablet created the greatest amount of fizzing? Which one created the least amount of fizzing?

Explain how temperature affects the rate of a reaction.

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Cold Room Temperature Hot