Energy in Chemical Reactions

Energy Changes in Chemical Reactions Tutorial

by David Blankenship

Multiple Select

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Fireworks are chemical reactions that release energy. Which of these phenomena are caused by chemical reactions that release energy? If you’re not sure, make a guess.Select all the correct answers.

Fireworks are chemical reactions that release energy. Which of these phenomena are caused by chemical reactions that release energy?

If you’re not sure, make a guess.

• Muscles work to perform a task.

• Fuel burns and heats the surroundings.

• A car's air bag expands by igniting a chemical.

• Plants use sunlight and atmospheric gases to make food.

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Some chemical reactions absorb energy rather than release it. Which of these phenomena are caused by chemical reactions that absorb energy? If you’re not sure, make a guess.

• A battery supplies current to a device.

• A person activates a cold pack by hitting it against a surface.

• A rechargeable battery is plugged in to charge.

• Heat is used to separate a compound into its elements

Multiple Choice

 

a reaction that releases energy

in the form of an electric current

• respiration

• photosynthesis

• electrochemical reaction

• combustion

Multiple Choice

 

a reaction that uses oxygen and

releases heat and light energy

• respiration

• photosynthesis

• electrochemical reaction

• combustion

Multiple Choice

 

a reaction in which plants absorb

energy from the Sun

• respiration

• photosynthesis

• electrochemical reaction

• combustion

Multiple Choice

 

a reaction carried out by cells that

use oxygen and release energy

• respiration

• photosynthesis

• electrochemical reaction

• combustion

Multiple Choice

What has to happen before a reaction takes place?

• Product molecules must collide

• Product molecules must collide with enough power

• Reacting molecules must collide with enough energy

• Molecules must collide with enough power

Multiple Choice

 

energy that a substance has because

of the arrangement of its atoms

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

Explain how increasing concentrations increases the rate of a reaction

• Less collisions occur

• More movement

• More collisions occur

• Less movement

Multiple Choice

What change in condition increases the speed of the reacting molecules?

• Decreasing temperature

• Increasing temperature

• Decreasing energy

• Increasing power

Multiple Choice

 

A measure of the average kinetic

energy of particles

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

 

The process of breaking down an

existing set of substances to

form a new set of substances

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

 

a phase in a reaction in which

existing bonds break to form

new bonds

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

 

A measure of the average kinetic

energy of particles

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

 

Energy required to start a reaction

• chemical energy

• transition state

• chemical reaction

• activation energy

• temperature

Multiple Choice

How can you increase the surface area of a solid?

• Divide the solid into smaller pieces

• Get more solid

• Turn it into a gas

Multiple Choice

Which change in condition only affects reactions involving gases?

• Temperature

• Surface area

• Pressure

• Concentration

Multiple Choice

What is the activation energy in a reaction?

• The energy needed for products to be formed

• The energy needed to break products into reactants

• The minimum energy needed to make products

• The minimum energy needed by reactants for them to react

Multiple Choice

What does a catalyst do?

• Speeds up reactants

• Speeds up a chemical reaction

• Speeds up products

• Speeds up particles

Multiple Choice

What do you call a biological catalyst?

• Product

• Reactant

• Biological reaction

• Enzyme

Fill in the Blank

Type the correct answer in the box. Round your answer to the nearest whole number.

When oxygen reacts with hydrogen, it has the capacity to release 29 kilojoules of energy. Inside a fuel cell, oxygen reacts with hydrogen to produce 23 kilojoules of useful energy. The rest of the energy is lost as heat. What’s the efficiency percentage of the fuel cell?

The efficiency of the fuel cell is  __________percent.

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Which sentences describe an advantage of using a hydrogen fuel cell instead of burning fossil fuels?

• The reaction of hydrogen and oxygen conveniently takes place inside a fuel cell.

• The combustion reaction of hydrogen and oxygen has a very low efficiency.

• Someday, it may be possible to produce hydrogen fuel using sunlight and water.

• The reaction of hydrogen and oxygen doesn’t create products that negatively affect the environment.