Chemistry Lesson: Matter and Change

​Energy and Change

​What is Energy

Energy is the capacity to do work or​ the ability to cause change. Energy is measured in Joules.

Physical and Chemical changes involve changes in energy.​

A physical change does not involve changing the identity of the substance while a chemical change does.​

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Multiple Choice

Chopping Wood is a

• Chemical Change

• Physical Change

​Every Change in Matter involves a Change in Energy

​Law of Conservation of Energy.

Forms of Energy.

Potential

Kinetic​

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​Conservation of Energy in Chemical Reactions

​

Energy is released by the system to the surrounding.

Final change in energy is negative.​

​Exothermic

Energy is absorbed by the system from the surrounding.

Final change in energy is positive​

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​Endothermic

​Types of Energy Changes

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Multiple Choice

Boiling is an exothermic process

• True

• False

Multiple Choice

Freezing is an Exothermic process

• True

• False

​Heat

​Heat is the transferred between two objects that are different in temperature.

Energy is always transferred from objects with high temperature to the objects with lower energy.​

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​Temperature

​Temperature is a measure of the average kinetic energy of a substance.

The higher the kinetic energy the higher the temperature.

Units of Temperature

Celsius

Kelvin: T(K)= t(C) +273​

O Kelvin is known as Absolute Zero​

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​Heating Curves

​What is the MP and BP shown in this graph?

Multiple Choice

The temperature remains constant during phase changes

• True

• False

Multiple Choice

As the substance is heated and approaches its melting point the kinetic energy of its particles

• Increases

• Decreases

• Stays the same

Multiple Choice

The energy added during boiling is expressed as

• Kinetic energy

• Potential energy

​Heat Transfer Affects Substances Differently

Some substances are heat up more quickly than others, depending a characteristic property ​called Specific Heat Capacity (c).

Specific heat capacity is the amount of energy needed to change the temperature of 1g of a substance by 1degree celsius or Kelvin.

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Multiple Choice

Metals change in their temperature quickly because it has a --------

• low specific heat capacity

• high specific heat capacity

Multiple Choice

On a hot summer day the sand on the beach is much hotter than the seawater because

• water has a low specific heat capacity

• water has a high specific heat capacity and sand has a low specific heat capacity

• sand has a high specific heat capacity

• none