Matter: Energy Changes in Chemical Reactions
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Questions and Answers

Which statement best describes reactions that release energy?

  • They can start without any initial energy input.
  • They necessarily absorb energy from their surroundings.
  • They always require continuous input of energy to proceed.
  • They might require some initial energy to start, but then release energy. (correct)

According to the information provided, energy can be created during a chemical reaction.

False (B)

What is a key question regarding energy changes in chemical reactions based on the content?

Why do some reactions give off thermal energy and some absorb thermal energy?

Reactions that release energy may require some initial energy to get ______.

<p>started</p> Signup and view all the answers

Match the statements with the phase they describe for change of mind after the lesson:

<p>Reactions that release energy require energy to get started. = May Agree Energy can be created during a chemical reaction. = Disagree</p> Signup and view all the answers

Based on the text, what is the primary focus of the lesson?

<p>Energy changes during chemical reactions. (B)</p> Signup and view all the answers

Reactions that absorb thermal energy give off energy as heat.

<p>False (B)</p> Signup and view all the answers

What type of energy is highlighted as being released or absorbed in a chemical reaction according to the text?

<p>thermal energy</p> Signup and view all the answers

What effect does increasing the concentration of reactants have on a chemical reaction?

<p>It increases collisions, resulting in a faster reaction rate. (D)</p> Signup and view all the answers

The law of conservation of energy states that energy can be created and destroyed.

<p>False (B)</p> Signup and view all the answers

What happens to energy when chemical bonds form?

<p>Energy is either absorbed or released.</p> Signup and view all the answers

In a hot pack, energy moves to the environment as it is released by the chemical _________ of the reactants.

<p>bonds</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Reaction rate = The speed at which a chemical reaction occurs Conservation of energy = The principle that total energy remains constant Hot pack = A system that releases energy to its surroundings Cold pack = A system that absorbs energy from its surroundings</p> Signup and view all the answers

What happens to the energy when plants are eaten by animals?

<p>Energy is transferred to the consumer. (C)</p> Signup and view all the answers

When plants and animals die, the energy and matter contained in their tissues are destroyed.

<p>False (B)</p> Signup and view all the answers

Besides thermal energy, what is another way energy can return to the environment when organisms die?

<p>Recycling by decomposers</p> Signup and view all the answers

What happens when atoms collide with the correct amount of force?

<p>The bonds between the atoms break. (A)</p> Signup and view all the answers

The formation of chemical bonds requires energy input.

<p>False (B)</p> Signup and view all the answers

When atoms form bonds, what forms of energy do they release?

<p>light or heat</p> Signup and view all the answers

The energy released when atoms form bonds is called chemical ______ energy.

<p>potential</p> Signup and view all the answers

What does chemical potential energy depend on?

<p>The arrangement and strength of the bonds. (A)</p> Signup and view all the answers

All chemical reactions only release energy.

<p>False (B)</p> Signup and view all the answers

How can temperature changes in hot and cold packs be explained, considering that all reactions both absorb and release energy?

<p>The transfer of energy in different ways can be tracked as energy flows through a system.</p> Signup and view all the answers

In an exothermic reaction, what is the relationship between energy released during product formation and energy required to break reactant bonds?

<p>More energy is released when the products form than is required to break the bonds in the reactants. (A)</p> Signup and view all the answers

In an exothermic reaction, thermal energy is written on the reactants side of the chemical equation.

<p>False (B)</p> Signup and view all the answers

What does the prefix 'exo-' mean in the term 'exothermic'?

<p>outside</p> Signup and view all the answers

The bonds of the _________ contain more energy than the bonds of the products in an exothermic reaction.

<p>reactants</p> Signup and view all the answers

What is the role of chemical reactions in living organisms?

<p>To supply energy to their cells. (A)</p> Signup and view all the answers

Plants use photosynthesis to release energy.

<p>False (B)</p> Signup and view all the answers

What two types of atoms are produced when plant cells split water during photosynthesis?

<p>hydrogen and oxygen</p> Signup and view all the answers

What causes a hot pack to become hot?

<p>A chemical reaction releases energy to the surroundings. (D)</p> Signup and view all the answers

All chemical bonds release and absorb the same amount of energy.

<p>False (B)</p> Signup and view all the answers

What forms of energy are released in a firework?

<p>thermal energy, light, and sound</p> Signup and view all the answers

Chemical reactions where more energy is required to break the bonds of the reactants than is released when products form are called ______ reactions.

<p>endothermic</p> Signup and view all the answers

In an endothermic reaction, where does thermal energy appear in the chemical equation?

<p>On the side with the reactants (A)</p> Signup and view all the answers

What causes a cold pack to become cold?

<p>It absorbs energy from the surroundings. (C)</p> Signup and view all the answers

The type of elements and compounds involved in a chemical reaction does not affect the overall change in energy.

<p>False (B)</p> Signup and view all the answers

What causes the temperature change in a chemical reaction?

<p>Changes in the energy of the system (B)</p> Signup and view all the answers

Energy changes in chemical reactions only come from the surrounding environment.

<p>False (B)</p> Signup and view all the answers

What is always moving?

<p>all matter</p> Signup and view all the answers

The more energy particles have, the more they move and with one another.

<p>collide</p> Signup and view all the answers

Match the following:

<p>Hot packs = Temperature increase Cold packs = Temperature decrease Energy = Movement of particles</p> Signup and view all the answers

In hot and cold packs, how is a temperature change achieved?

<p>By mixing specific chemicals together (B)</p> Signup and view all the answers

The temperature change of a system only depends on collisions between particles.

<p>False (B)</p> Signup and view all the answers

Where does the energy from a chemical reaction come from?

<p>chemical bonds or the surrounding environment</p> Signup and view all the answers

Flashcards

Chemical Reaction

A process involving the rearrangement of atoms and molecules, resulting in the formation of new substances with different properties.

Exothermic Reaction

Energy released during a chemical reaction, often in the form of heat or light.

Endothermic Reaction

Energy absorbed during a chemical reaction, often requiring an input of heat.

Activation Energy

The minimum amount of energy required to initiate a chemical reaction.

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Enthalpy Change

The total energy change during a chemical reaction, calculated as the difference between the energy of the products and reactants.

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Exothermic Reaction

A chemical reaction that releases heat to the surroundings, causing a temperature increase.

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Endothermic Reaction

A chemical reaction that absorbs heat from the surroundings, causing a temperature decrease.

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Specific Heat Capacity

The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

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Bond Energy

The amount of energy required to break the bonds of reactants in a chemical reaction.

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Chemical Equation

A representation of a chemical reaction showing reactants, products, and energy flow.

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Heat Transfer in a Hot Pack

Thermal energy is transferred from the hot pack to the surroundings, causing it to become hot.

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Energy Transfer

The change in energy content of a system during a physical or chemical change.

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Chemical Bond Energy

The energy stored within the chemical bonds of a substance.

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Internal Energy

The sum of all the kinetic and potential energies of the particles in a system.

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Heat Transfer

The transfer of energy between objects or systems due to a temperature difference.

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Thermochemistry

The study of energy changes associated with chemical reactions.

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Bond Breaking Requires Energy

The energy needed to break bonds between atoms during a chemical reaction.

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Bond Formation Releases Energy

The energy released when atoms form bonds during a chemical reaction.

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Chemical Potential Energy

Energy stored within chemical bonds, released when bonds break.

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Chemical Potential Energy and Bond Strength

The amount of chemical potential energy depends on the arrangement and strength of bonds.

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Energy Flow in Chemical Reactions

The exchange of energy as it flows through a system during a chemical reaction.

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Energy Balance in Reactions

The difference in energy absorbed and released determines whether a reaction feels hot or cold.

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Photosynthesis

The process by which plants and some unicellular organisms use the Sun's energy to convert light energy into chemical energy.

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Exothermic Process

A chemical reaction that releases energy, typically as heat.

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Endothermic Process

A chemical reaction that absorbs energy, often as heat.

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How Concentration Affects Reactions

More collisions between particles lead to a faster reaction. Increasing the concentration of reactants brings particles closer, boosting collisions.

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Law of Conservation of Energy

Energy isn't created or destroyed, just moves around. Chemical reactions either absorb energy (endothermic) or release it (exothermic).

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Energy in Chemical Reactions

Chemical reactions use energy to break bonds in reactants and release energy when new bonds are formed in products.

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Energy Flow in Ecosystems

Plants store energy in glucose, which is passed to animals when they eat. Energy returns to the environment through heat from organisms and decomposition.

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Hot Packs and Cold Packs

A hot pack releases energy into the surroundings, making it feel hot. A cold pack absorbs energy from the surroundings, making it feel cold.

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Overall Energy Remains Constant

The total amount of energy in a system stays the same, even if it's being transferred around.

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Study Notes

Matter: Properties and Changes - Energy Changes in Chemical Reactions

  • Chemical reactions involve energy transfers—some release energy, others absorb it.
  • Reactions that release energy don't need energy to start. Energy is released during the reaction.
  • Energy is not created or destroyed in a chemical reaction, it's transferred between chemical bonds and the surroundings.
  • Energy in chemical reactions comes from the chemical bonds holding the reacting atoms together or from the surroundings.
  • Chemical bonds breaking requires energy, while forming bonds releases energy.
  • The arrangement and strength of the bonds in a substance determine its chemical potential energy.
  • Hot packs release energy, causing a temperature increase. This is an exothermic reaction.
  • Cold packs absorb energy, causing a temperature decrease. This is an endothermic reaction.
  • Energy transfers constantly occur between atoms and the environment.
  • The amount of energy released or absorbed during a chemical reaction depends on the type of chemical bonds breaking and forming.
  • The law of conservation of energy states energy can't be created or destroyed, only transferred.
  • Organisms use chemical reactions to provide energy for their cells.
  • Photosynthesis converts sunlight into chemical energy, and cellular respiration releases energy stored in the bonds of molecules like glucose.
  • The concentration of reactants affects the speed of the reaction. Higher concentrations lead to more frequent collisions, speeding up the reaction, and influencing products.

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Reading Essentials Energy Changes in Chemical Reactions PDF

Description

Explore the fascinating energy changes that occur in chemical reactions. This quiz covers concepts such as exothermic and endothermic reactions, energy transfer between bonds, and how these processes affect temperature. Test your understanding of how energy behaves in chemical transformations.

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