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Conservation of Mass in Reactions — Reading Comprehension

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This science reading passage for grades 6-8 dives into the concept of conservation of mass during chemical reactions, emphasizing its importance in both closed and open systems. Using everyday examples like the reaction between baking soda and vinegar, students learn how mass is neither created nor destroyed, but can appear to change if gases escape from an open system. The passage explains the underlying mechanisms, the scientific processes involved, and includes vocabulary support, a glossary, and comprehension activities. It aligns with NGSS standard MS-PS1-5 and reinforces scientific thinking by analyzing real experiments and the cause-and-effect relationships in nature. The passage is audio integrated and includes graphic organizers and Spanish translations to support diverse learners.

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law-of-conservation-of-mass-2 — Lavoisier's mercury experiment demonstrated conservation of mass

Conservation of mass is a fundamental principle in science stating that the total mass of substances does not change during a chemical reaction. When baking soda is mixed with vinegar in a sealed container, the total mass of the system remains the same, regardless of the changes happening inside. This principle is crucial for understanding chemical reactions and predicting the outcomes of experiments in both laboratories and daily life.

How Conservation of Mass Works

During a chemical reaction, substances called reactants are transformed into new substances known as products. Although the appearance, state, or energy of substances may change, the total amount of matter stays constant. This is because atoms, the building blocks of matter, are simply rearranged, not created or destroyed. For example, when baking soda (sodium bicarbonate) and vinegar (acetic acid) react, they produce carbon dioxide gas, water, and sodium acetate. In a closed system, like a tightly sealed flask, the mass before and after the reaction is identical. Scientists measure this using precise balances to confirm that mass is conserved.

Apparent Mass Loss in Open Systems

Sometimes, it looks like mass has been lost during a reaction. This usually happens in an open system, where substances such as gases can escape. If you perform the baking soda and vinegar reaction in an open beaker, bubbles of carbon dioxide rise and leave the container. As a result, the mass measured afterward appears lower. However, the lost mass is not destroyed; it has simply left the system as a gas. Scientific experiments show that if the escaping gas is captured and measured, the total mass still matches the original amount.

Real-World Applications and Broader Implications

The law of conservation of mass is not just important for classroom experiments. It is essential in industrial chemistry, environmental science, and even cooking. For instance, engineers designing power plants must account for all materials entering and leaving a system to avoid pollution. Environmental scientists use this law to track pollutants in air and water. Understanding conservation of mass also helps explain natural cycles, such as the carbon cycle, where carbon moves between the atmosphere, plants, animals, and soil without any loss of mass. This principle connects to larger scientific ideas about the stability and predictability of natural systems.

In summary, the conservation of mass demonstrates that matter is neither created nor destroyed in chemical reactions, only changed in form. Observing mass changes in open and closed systems helps scientists understand where materials go, and why certain changes occur. Recognizing this law is essential for scientific thinking and problem-solving in real life.

Interesting Fact: French scientist Antoine Lavoisier first demonstrated the law of conservation of mass in the late 1700s by carefully measuring chemical reactions in sealed containers.

What does the law of conservation of mass state?

Mass is not created or destroyed during a chemical reaction.Mass increases during chemical reactions.Mass always decreases in open systems.Mass disappears when gases escape.

What happens if you mix baking soda and vinegar in a closed container?

The total mass remains the same before and after the reaction.The total mass increases.The mass disappears.Only the gas is measured.

Which is a correct definition of 'reactants'?

The starting substances in a chemical reaction.The products formed after a reaction.The gases that escape.The amount of mass lost.

Which word best describes a system where matter can leave or enter?

Open systemClosed systemReactantAtom

Why does mass appear to decrease in an open system during a reaction?

Gases produced can escape into the air.Atoms are destroyed.New mass is created.Reactants disappear completely.

What scientific tool do scientists use to measure mass?

BalanceThermometerBeakerMicroscope

In the carbon cycle, what happens to carbon atoms?

They move between the atmosphere, plants, animals, and soil.They are destroyed in chemical reactions.They become gas and disappear.They only stay in plants.

Which statement is true about closed systems?

Matter cannot enter or leave during a reaction.Gases can escape into the air.Mass always increases.Only products exist.

True or False: In a closed system, the total mass before and after a reaction is different.

TrueFalse

True or False: The law of conservation of mass helps scientists track pollution and resources.

TrueFalse

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