Physical Science 2-4: Properties of Gases

​Physical Science 2-4: Properties of Gases

Multiple Choice

What is a physical property of these strawberries?

• Red

• Rotten

• Flammable

Multiple Choice

What is a chemical property of paper?

• Flammable

• White

• Light

Multiple Choice

Is an ice cream cone melting a physical or chemical change?

• Physical

• Chemical

Multiple Choice

Is toasting bread a physical or chemical change?

• Physical

• Chemical

Multiple Choice

The ability to rust is a

• Physical property

• Chemical property

Multiple Choice

The element iron is very magnetic. This is an example of a

• Physical property

• chemical property

Lesson Objectives

• Describe factors that affect how a gas behaves

• Use Boyle's law to predict the behavior of a gas

• Use Charles's law to predict the behavior of a gas

Introduction to Gases

• The properties of different states depend on how the particles move in that state of matter

• Gas particles move quickly and spread out to fill the volume of the container

• How much space a gas takes up is dependent on three factors

  • temperature

  • volume

  • pressure

Temperature

• Temperature: Measures the amount of kinetic energy in a substance

  • Tells you how fast the particles are moving

  • We can feel temperature as heat, but heat is not what is being measured

• As the temperature increases, the amount of energy the particles have increases, and they move faster and spread out

• As the temperature decreases, the amount of energy the particles have decreases, and they move more slowly and stay closer together

Volume

• Because gas particles do not stick together, they are able to spread out and take up more space

• The Volume of a gas is dependent on the size of the container it is in

  • If you have a rigid container, the gas particles will be pushed closer together

  • If you have a flexible container, it will expand with the gas

Pressure

• Pressure: The amount of force that is put on an area

• When particles are close together, they exert pressure on the particles around them

  • If you have more particles, they exert more pressure

  • If you have particles moving with more energy, they exert more pressure

What are the Gas Laws?

• When you have a gas, the temperature, pressure, and volume are all related to one another and affect each other.

• Gas Laws are a set of equations that help to describe the relationships between the different variables that affect a gas

• In this class, we will look at two of the gas laws

  • Boyle's Law

  • Charles's Law

Boyle's Law

• Boyle's Law: The Volume of a gas is inversely proportional to the pressure of the gas when the temperature is constant

  • As the pressure increases, the volume decreases

Boyle's Law Sample Problem 1

• A gas that originally occupies 22.4 liters has its pressure increased from 760 mmHg to 1520 mmHg. What is the new volume?

  • Step 1: Identify your Variables

    • P₁₌

    • V₁=

    • P₂=

    • V₂=

  • Step 2: Plug your Variables into the Boyle's Law Equation

Boyle's Law Sample Problem 1

• A gas that originally occupies 22.4 liters has its pressure increased from 760 mmHg to 1520 mmHg. What is the new volume?

  • Step 1: Identify your Variables

    • P₁₌760

    • V₁= 22.4

    • P₂=1520

    • V₂=?

  • Step 2: Plug your Variables into the Boyle's Law Equation and solve for your unknown

Boyle's Law Sample Problem 2

• A weather balloon contains 59.5 L of helium at sea level, where the pressure is 101.3 kPa. The balloon is released from a mountaintop where the pressure is 61.7 kPa. What is the volume of the balloon when it is released?

  • Step 1: Identify your Variables

    • P₁=

    • V₁=

    • P₂=

    • V₂=

  • Step 2: Plug your Variables into the Boyle's Law Equation

Boyle's Law Sample Problem 2

• A weather balloon contains 59.5 L of helium at sea level, where the pressure is 101.3 kPa. The balloon is released from a mountaintop where the pressure is 61.7 kPa. What is the new volume of the balloon when it is released?

  • Step 1: Identify your Variables 

    • P₁= 101.3

    • V₁=59.5

    • P₂= 61.7

    • V₂=?

  • Step 2: Plug your Variables into the Boyle's Law Equation and Solve

Boyle's Law Sample Problem 3

• What pressure will be needed to reduce the volume of 77.4 L of helium at 98.0 kPa to a volume of 60.0 L?

  • Step 1: Identify your Variables

    • P₁=

    • V₁=

    • P₂=

    • V₂=

  • Step 2: Plug your Variables into the Boyle's Law Equation

Boyle's Law Sample Problem 3

• What pressure will be needed to reduce the volume of 77.4 L of helium at 98.0 kPa to a volume of 60.0 L?

  • Step 1: Identify your Variables

    • P₁= 98.0

    • V₁= 77.4

    • P₂= ?

    • V₂=60.0

  • Step 2: Plug your Variables into the Boyle's Law Equation

Multiple Choice

What is the formula for Boyle's Law?

• P₁V₁=P₂V₂
• P₁V₁/P₂V₂
• P₁V₂=P₂V₁
• P₁/V₁=P₂/V₂

Charles's Law

• Charles's Law: the volume of a gas is directly proportional to the temperature of a gas when the pressure is constant

  • As you increase the temperature of a gas, the Volume will increase

Charles's Law Sample Problem 1

• A weather balloon contains 5.30 kL of helium gas when the temperature is 285 Kelvin. At what temperature will the balloon’s volume have increased to 6.00 kL?

  • Step 1: Identify your Variables

    • V₁=

    • T₁=

    • V₂=

    • T₂=

  • Step 2: Plug your Variables into Charles' Law Equation

Charles's Law Sample Problem 1

• A weather balloon contains 5.30 kL of helium gas when the temperature is 285 Kelvin. At what temperature will the balloon’s volume have increased to 6.00 kL?

  • Step 1: Identify your Variables

    • V₁= 5.30

    • T₁= 285

    • V₂= 6.00

    • T₂= ?

  • Step 2: Plug your Variables into Charles' Law Equation

Charles's Law Sample Problem 2

• A balloon is inflated with 6.22 L of helium at a temperature of 309 Kelvin. What is the volume of the balloon when the temperature is 295 Kelvin?

  • Step 1: Identify your Variables

    • V₁=

    • T₁=

    • V₂=

    • T₂=

  • Step 2: Plug your Variables into Charles' Law Equation

Charles's Law Sample Problem 2

• A balloon is inflated with 6.22 L of helium at a temperature of 309 Kelvin. What is the volume of the balloon when the temperature is 295 Kelvin?

  • Step 1: Identify your Variables

    • V₁= 6.22

    • T₁= 309

    • V₂= ?

    • T₂= 295

  • Step 2: Plug your Variables into Charles' Law Equation

Charles's Law Sample Problem 3

• A balloon has a volume of 10.50 L if the temperature is 288 Kelvin. If the temperature is 238 Kelvin, what will be the volume of the balloon?

  • Step 1: Identify your Variables

    • V₁=

    • T₁=

    • V₂=

    • T₂=

  • Step 2: Plug your Variables into Charles' Law Equation

Charles's Law Sample Problem 3

• A balloon has a volume of 10.50 L if the temperature is 288 Kelvin. If the temperature is 238 Kelvin, what will be the volume of the balloon?

  • Step 1: Identify your Variables

    • V₁= 10.50

    • T₁= 288

    • V₂= ?

    • T₂= 238

  • Step 2: Plug your Variables into Charles' Law Equation

Multiple Choice

What is the formula Charles' Law?

• V = T
• VT = VT
• T₁ / V_{1 =} T₂ / V₂
• V₁ / T₁ = V₂ / T₂