Diffusion of Gases

Multiple Choice

Look at the pressure triangle. How do we calculate the area?

• f ÷ a
• f x p
• p x f
• f ÷ p

Multiple Choice

What is pressure?

• The amount of force exerted on a surface

• The surface area of an object

• The weight of an object

Multiple Choice

What is the equation used to calculate pressure?

• pressure= force/mass
• pressure =mass/volume
• pressure=area/force
• pressure=force/area

Multiple Choice

What is the unit of measurement for pressure?

• N/m2

• grams
• milliters
• meters

Multiple Choice

The pressure resulting from a force of 50 N exerted over an area of 5 m² is

• 10 N
• 0.1 N
• 10 N/m²

• 0.1 Pa

Open Ended

In your own words, explain why it's safer to stand on many nails than standing on one nail.

Multiple Choice

Which of the statements is true?

• The bottom of the boot exerts more pressure than the shoe as a result of an increase in surface area.
• The bottom of the shoe exerts more pressure than the boot as a result of an decrease in surface area.
• The bottom of the shoe exerts the same pressure as the bottom of the boot.

Multiple Choice

What pressure does a 4000N horse exert on the ground if each foot is 10cm²?

• 40 N/cm²
• 100 N/cm²
• 400 N/cm²
• 10 N/cm²

Multiple Choice

Army tank tracks are useful for travelling through the mud because..

• they decrease the force the vehicle exerts on the ground

• they increase the force the vehicle exerts on the ground

• they decrease the pressure the vehicle exerts on the ground

• they increase the pressure the vehicle exerts on the ground

Multiple Choice

The amount of perpendicular force acting on an area is the definition of....

• Fluid
• Viscosity
• Barometer
• Pressure

Multiple Choice

Pressure is equal to force divided by what

• area
• mass
• time
• distance

Multiple Choice

What is the equation used to calculate pressure?

• pressure= force/mass
• pressure =mass/volume
• pressure=area/force
• pressure=force/area

Multiple Choice

What pressure does a 4000N horse exert on the ground if each foot is 10cm²?

• 40 N/cm²
• 100 N/cm²
• 400 N/cm²
• 10 N/cm²

Multiple Choice

A force of 225 N is applied to an area of 75 m². What is the pressure?

• 3 N/m²

• 5 N/m²

• 0.33 N/m²

• 0.2 N/m²

Multiple Choice

A force of 225 N is applied to an area of 75 m2. What is the pressure?

• 3 N/m2

• 16'875 N/m2

• 5 N/m2

• 0.33 N/m2

Multiple Choice

The pressure resulting from a force of 50 N exerted over an area of 5 m² is

• 10 N
• 0.1 N
• 10 N/m²

• 0.1 Pa

​How does depth affect pressure in a liquid?

​

The water spurts out furthest and fastest from the bottom hole.

​

This shows that the pressure is greatest at the bottom of the container.​

​

IGCSE Physics Textbook pp.106-109

​Video

https://www.youtube.com/watch?v=Cvp6mLWbgaM​

Gas pressure and diffusion

by Elmira Karimova

​Gas pressure

• The particles in a gas move quickly in all directions, but they do not get far before they collide with each other or with the walls of their container. Gas pressure is caused when gas particles hit the walls of their container. The more often the particles hit the walls, and the faster they are moving when they do this, the higher the pressure.

Heating increases pressure​

​If a gas is heated, its particles move around more quickly. They hit the walls of their container harder and more often. This increases the pressure. Sometimes the pressure gets so great that the container bursts.

​What's happening?

​Why is it happening?

​How is the process called?

​What is Diffusion?

Diffusion is the movement of a substance from an area of high concentration to an area of lower concentration .

​Diffusion occurs in liquids and gases when their particles collide randomly and spread out. Diffusion is an important process for living things - it is how substances move in and out of cells.

​Diffusion in everyday life

​Factors affecting diffusion

• ​The state of matter

• ​Temperature

• ​Consentration gradient

​The solid (steel) is the most dense, the gas (air) is the least dense, and the density of the liquid (water) is in between.

Solids

The particles in solids are very close together. They are tightly packed, giving solids high densities.

Liquids

The particles in liquids are close together. Although they are randomly arranged, they are still tightly packed, giving liquids high densities.

​Gases

The particles in gases are very far apart, so gases have a very low density.

Temperature

​

Materials are a store of internal energy, due to the motion of particles .

When a substance is heated, its internal energy increases:

• the movement of its particles increases

​Link: https://phet.colorado.edu/sims/html/diffusion/latest/diffusion_en.html

​Consentration Gradient

​The difference in the concentration of a substance between two areas is called the concentration gradient.

The bigger the difference, the steeper the concentration gradient and the faster the molecules of a substance will diffuse.

Q1

​When there is no wind, the scent of flowers can be detected more easily on a warm evening than on a cold evening.

This is because the molecules of the scent ............................. than in colder conditions.

​Q2

​Car exhausts can spread through the atmosphere.This occurs because gas molecules move from a region of ...... 1...... concentration to a region of

...... 2 ...... concentration by a process called 3......