Investigating Chemical Reactions and Mass Conservation
Science Lab · Grade 7
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Type
science_lab
Pre Lab
Background: Have you ever wondered what happens to matter when it seems to disappear? When you drop an antacid tablet into water, it fizzes and appears to vanish — but where does it go? To understand this, scientists use the **kinetic molecular theory (KMT)**, which states that all matter is made of tiny **particles** that are constantly moving. The faster the particles move, the more energy they have. **Temperature** is a measure of the average kinetic energy of those particles, so higher temperatures mean faster-moving particles.
When baking soda (sodium bicarbonate) and vinegar (acetic acid) are mixed, a **chemical reaction** occurs. Unlike a physical change — such as **dissolution**, where a substance like sugar mixes into water but can be recovered, or **evaporation**, where liquid water becomes water vapor through a **phase change** — a chemical reaction produces entirely new substances. In this reaction, carbon dioxide gas, water, and sodium acetate are formed. The fizzing you see is the carbon dioxide gas escaping as bubbles, which is evidence that a chemical reaction has taken place.
But here is the key question: does matter disappear during this reaction? According to the law of **conservation of mass**, the total mass of the reactants must equal the total mass of the products. Even though the carbon dioxide gas escapes into the air, the atoms that made it up still exist — they have simply changed form. In this lab, you will design your own investigation to test how temperature affects the speed of this chemical reaction while also exploring whether mass is truly conserved.
Vocabulary
Term: kinetic molecular theory (KMT)
Definition: A scientific model stating that all matter is made of tiny particles in constant motion, and that the speed of those particles increases with temperature.
Term: KMT
Lab Type
Post Lab
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Safety Level
Teacher Notes
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Experiment Design
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