Practice questions on Conservation of Mass in chemical and physical changes

📚 Topic Summary

The Law of Conservation of Mass states that mass is neither created nor destroyed in ordinary chemical reactions and physical transformations. In simpler terms, the mass of the products in a chemical reaction must equal the mass of the reactants. This means that the total number of atoms of each element remains constant during the reaction, even though they may be rearranged. We use this principle to balance chemical equations and predict the amount of reactants needed or products formed in a reaction.

In physical changes, like melting ice or dissolving sugar in water, the substance changes its form but not its chemical identity. Therefore, the mass remains constant during these processes. For example, if you melt 10 grams of ice, you'll end up with 10 grams of water. This principle is super useful for solving all sorts of science problems! 🧮

🧪 Part A: Vocabulary

Match the terms with their definitions:

📝 Part B: Fill in the Blanks

Complete the following paragraph using the words: mass, atoms, conserved, chemical, physical.

The Law of Conservation of ______ states that in any ______ reaction or ______ change, the total ______ remains constant. This means that the number of ______ of each element is ______ throughout the process. No atoms are created or destroyed; they are simply rearranged.

🤔 Part C: Critical Thinking

A student performs an experiment where they react 10.0 g of sodium bicarbonate ($\NaHCO_3$) with 15.0 g of hydrochloric acid ($\HCl$) in an open container. After the reaction, they measure the mass of the remaining solution to be 23.0 g. Explain why the final mass is less than the initial combined mass, even though mass is conserved. Where did the missing mass go? 💨