MS-PS1-2: Chemical Interactions

MS-PS1-2
Chemical Interactions

Middle School

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Learning Objectives

• Analyze data on properties to determine if a chemical reaction has occurred.

• Describe how atoms rearrange to form new substances with different properties.

• Explain that the total number and types of atoms are conserved during chemical reactions.

• Use balanced chemical equations to model the law of conservation of matter.

Key Vocabulary

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Chemical Reaction

A process where reactants undergo a change to form entirely new substances, known as products.

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Reactants

These are the original ingredients or starting substances present at the beginning of a chemical reaction.

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Products

Products are the new substances that are formed as a result of a chemical reaction.

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Conservation of Matter

This principle states that matter is not created or destroyed during any chemical reaction.

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Physical Property

A characteristic of a substance that can be observed or measured without changing its identity.

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Chemical Property

A property that becomes evident during a chemical reaction, indicating a substance's potential to change.

Key Vocabulary

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Density

Density is the measure of how much mass is packed into a certain volume.

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Solubility

Solubility describes the ability of a substance, the solute, to dissolve in another substance, the solvent.

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Flammability

Flammability refers to the ability of a chemical or substance to burn or ignite, causing a fire.

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Odor

Odor is the property of a substance that gives it a distinctive or characteristic smell.

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Balanced Equation

A balanced equation is a chemical equation where the number of atoms for each element is equal.

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Precipitate

A precipitate is a solid substance that forms from a solution during a chemical reaction.

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Characteristic Properties of Matter

Physical Properties

• Physical properties can be observed or measured without changing the chemical identity of the substance.

• Examples include density, melting point, boiling point, and the ability of a substance to dissolve.

• These unique properties can be used to identify an unknown pure substance under specific conditions.

Chemical Properties

• Chemical properties describe a substance's ability to change into a new and different substance.

• These properties are only observable during a chemical reaction, which alters the substance's composition.

• A key example is flammability, which is the ability of a substance to burn.

Multiple Choice

What is the main purpose of using the characteristic properties of a substance?

• To identify an unknown pure substance

• To determine the color of a substance

• To change the substance into something new

• To measure the mass of a substance

Multiple Choice

What is the key difference between a physical property and a chemical property?

• A physical property describes its color, while a chemical property describes its shape.

• A physical property can be observed without changing the substance's identity, while a chemical property involves a change into a new substance.

• A physical property involves burning, while a chemical property involves melting or boiling.

• A physical property can only be measured in a lab, while a chemical property can be seen anywhere.

Multiple Choice

A student observes that a piece of wood burns and turns into ash. How would this observation be classified and why?

• A physical property, because the wood's ability to burn was observed.

• A chemical property, because the wood was changed into a new substance (ash).

• A physical property, because the change could be easily reversed.

• A chemical property, because it describes a physical change in the wood.

Phase Changes and Particle Bonds

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Solids

• ​Particles in a solid are held in fixed positions.

• ​​They are tightly packed together with very strong bonds.

• ​The particles can only vibrate in their fixed places.

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Liquids

• ​Particles in a liquid are close but can move around.

• ​​The bonds between the liquid particles are weaker than solids.

• ​Liquids can flow and take the shape of containers.

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Gases

• ​Gas particles are very far apart from each other.

• ​​There are no real bonds between the gas particles.

• ​They move around quickly and randomly in all directions.

Multiple Choice

What is the main factor that determines if a substance is a solid, liquid, or gas?

• The strength of the bonds holding its particles together.

• The size of the individual particles.

• The speed at which the particles are vibrating.

• The shape of the container the substance is in.

Multiple Choice

What is the key difference in the arrangement and movement of particles between a solid and a liquid?

• Liquid particles have weaker bonds and can move past one another, while solid particles are held in fixed positions.

• Solid particles are much farther apart than liquid particles.

• Liquid particles can only vibrate, while solid particles can flow freely.

• Solid particles have no bonds, while liquid particles have very strong bonds.

Multiple Choice

If you observe a substance whose particles are spread very far apart and are moving quickly and randomly, what conclusion can you draw?

• It is a gas, because its particles are far apart and have no real bonds.

• It is a liquid, because its particles are able to move around.

• It is a solid, because its particles are held tightly by strong bonds.

• It is a liquid, because it is taking the shape of a container.

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What is a Chemical Reaction?

Reactants

• ​Reactants are the starting substances in a chemical reaction before they are mixed.

• ​​Bonds between the atoms of the reactants are broken during the reaction.

• ​Initially, they might be clear liquids that have no odor and are non-flammable.

Products

• ​Products are the entirely new substances that are formed after the chemical reaction.

• ​​New bonds are formed between atoms, creating the new substances called products.

• ​The formation of a yellow solid precipitate shows a new substance was made.

Multiple Choice

What are the starting substances in a chemical reaction called?

• Reactants

• Products

• Solids

• Liquids

Multiple Choice

How do reactants become entirely new products in a chemical reaction?

• The bonds between their atoms are broken and then new bonds are formed.

• They simply change their physical state, like from a liquid to a solid.

• They mix together but the atoms themselves do not change.

• They gain an odor and become flammable.

Multiple Choice

If two clear liquids are mixed and a yellow solid suddenly appears, what is the best conclusion?

• A new substance was formed, indicating a chemical reaction occurred.

• The two liquids did not mix and are separating.

• The original clear liquids simply changed color.

• The yellow solid was already present in one of the liquids.

Conservation of Matter & Balancing Equations

• The law of conservation of matter means atoms are never created or destroyed.

• A balanced equation has equal atoms on the reactant and product sides.

• We add coefficients like in 2H₂ + O₂ → 2H₂O to balance equations.

Multiple Choice

What does the law of conservation of matter state happens to atoms in a chemical reaction?

• Atoms are not created or destroyed, only rearranged.

• New atoms are created to form the products.

• Some atoms are destroyed during the reaction.

• Atoms can be changed into different elements.

Multiple Choice

What is the primary reason for balancing a chemical equation?

• To ensure the number of atoms is equal on both sides of the equation.

• To show which of the substances is the most important.

• To change the chemical properties of the substances.

• To make the total number of molecules equal on both sides.

Multiple Choice

In the example equation 2H₂ + O₂ → 2H₂O, what is the specific function of the coefficient '2' in front of H₂O?

• To show that two molecules of water are formed, which balances the hydrogen and oxygen atoms.

• To indicate that the water molecule is twice as large as the reactant molecules.

• To change the water (H₂O) into a different substance like hydrogen peroxide (H₂O₂).

• To show that the reaction needs to be performed twice to work correctly.

Types of Chemical Reactions

1. Combination (Synthesis): Two or more substances combine to form one. Example: 2H₂ + O₂ → 2H₂O

2. Decomposition: A compound breaks down into simpler substances. Example: 2H₂O₂ → 2H₂O + O₂

3. Single Displacement: One element replaces another in a compound. Example: Zn + 2HCl → ZnCl₂ + H₂

4. Double Displacement: Ions in two compounds exchange places. Example: NaCl + AgNO₃ → NaNO₃ + AgCl

5. Combustion: A substance reacts with oxygen, releasing energy. Example: CH₄ + 2O₂ → CO₂ + 2H₂O

Multiple Choice

What is the primary characteristic of a chemical reaction?

• A new substance is formed with different properties.

• A substance dissolves into another substance.

• A substance changes its state, like melting or freezing.

• A mixture is created, but no new substance is formed.

Multiple Choice

Based on the examples, what is the role of substances like iron (Fe) and zinc (Zn) in their respective chemical reactions?

• They are the new substances created by the reaction.

• They are the starting materials that are consumed in the reaction.

• They are the gases that are released during the reaction.

• They are the containers in which the reaction takes place.

Multiple Choice

The equation shows that zinc (Zn) and hydrochloric acid (HCl) are needed to produce hydrogen gas (H₂). What can you conclude would happen if only hydrochloric acid was present?

• The amount of hydrochloric acid (HCl) would double.

• Hydrogen gas (H₂) would not be produced.

• The reaction would produce zinc oxide instead.

• The reaction would occur, but at a much slower rate.

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Common Misconceptions

Misconception	Correction
Any change in appearance is a chemical reaction.	Physical changes alter appearance; chemical reactions create new substances.
New atoms are created in a chemical reaction.	Atoms are rearranged to form new products, not created.
Burning a substance completely destroys it.	Burning creates new substances like ash and CO2.
An equation is right with correct reactants and products.	Equations must be balanced, with equal atoms on each side.

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Summary

• Substances have unique properties; a change in them indicates a chemical reaction.

• In reactions, reactant atoms rearrange to form new products, conserving matter.

• Balanced chemical equations show that all atoms are conserved during a reaction.

• Reactions like combustion create new substances with entirely different properties.

Poll

On a scale of 1-4, how confident are you about analyzing chemical reactions and the conservation of matter?

• 1

• 2

• 3

• 4