PhysicsAtmospheric Pressurefor Matthayomsuksa 1

Vocabulary

atmospheric pressure(n.)

Vocabulary

experiment (n.)

Vocabulary

measurement (n.)

Vocabulary

barometer(n.)

Vocabulary

circumstance(n.)

Vocabulary

mass(n.)

Vocabulary

elevation (n.)

Vocabulary

overlying (v.)

Vocabulary

mercury (n.)

StructurePassive Voice

In passive sentences, the subject of the verb is not the person or thing (the “agent”) doing the action.

Structure

Subject + auxiliary verb (be) + main verb (past participle) + (by) +…

Note: the main verb is always in its past participle

form.

Structure

Use of the Passive VoiceWe use the passive when:

We want to make the active object more important.

We do not know the active subject.

Structure

Look at these examples:

1. Atmospheric pressure is closely approximated by the hydrostatic pressure.

subjectauxiliary

verb (be)

main verb (past

participle)

Look at these examples:

2. Standard Atmospheric Pressure is used as a reference for gas densities and volumes.

Structure

subjectauxiliary

verb (be)

main verb (past

participle)

StructureLook at these examples:

3. The Standard Atmospheric Pressure is defined at sea-level.

main verb (past

participle)

auxiliary verb (be)

subject

Look at these examples:

4. Any instrument that measures air pressure is called a barometer.

Structure

auxiliary verb (be)

main verb (past

participle)

subject

Text 3Atmospheric pressureAtmospheric pressure is the force per unit

area exerted into a surface by the weight of air above that surface in the atmosphere of Earth. In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point. Low-pressure areas have less atmospheric mass above their location, whereas high-pressure areas have more atmospheric mass above their location. Likewise, as elevation increases, there is less overlying atmospheric mass, so that pressure decreases with increasing elevation.

Standard Atmospheric Pressure

Standard Atmospheric Pressure (atm) is used as a reference for gas densities and volumes. The Standard Atmospheric Pressure is defined at sea-level at 273oK (0oC) and is 1.01325 bar or 101325 Pa (absolute). The temperature of 293oK (20oC) is also used.

Measuring Atmospheric PressureAny instrument that measures air pressure is called

a barometer. The first measurement of atmospheric pressure began with a simple experiment performed by Evangelista Torricelli in 1643. In his experiment, Torricelli immersed a tube, sealed at one end, into a container of mercury. Atmospheric pressure then forced the mercury up into the tube to a level that was considerably higher than the mercury in the container. Torricelli noticed that height of the mercury varied with changes in outside weather conditions. The most common type of barometer used in homes is the aneroid barometer

Figure 1: Diagram showing the construction of Torricelli's barometer.

Figure 2: Aneroid barometer.

Activity

Speaking

Writing

SpeakingExperiment Role-playSituation: You are in the science experiment

contest. You have to present your project, remember to give the following science process

1. Observation2. Hypothesis Forming3. Data Gathering4. Performing Experiement to test you hypothesis5. Results Recording

The rest of other groups are the committee and try to find out the faults by using some questions.

Make a group of 5 I will give you 10 minutes

Writing

Create your own experiment about “Atmospheric Pressure” by using the following materials:

Paper Glass Water

Then write on the paper and present in front of class.

Atmospheric Pressure.