Temperature

Chem 332

Temperature

• What is temperature?• Is it the same as heat?• How do thermometers

work?

Thermometers

• Bulb of mercury (usually) at the bottom of a glass tube

• Tube has marks at different heights

mercury

Low & High Temperatures

At low temperatures the column of mercury is near the bottom

At high temperatures the column of mercury is near the top

Why?

• What causes the mercury to go up or down?

Phases of Matter

• The answer lies in what we already know about matter.

• Solids consist of particles that are barely moving and are locked into position.

• Liquids consist of particles that have more energy are no longer locked into position and are able to move freely around each other.

• Gases consist of particles that have so much energy they are able to break completely free from each other and move around freely within their container.

Phases of matter

SOLID LIQUID GAS

Low energy. Particles barely moving

Medium energy. Particles moving more

High energy. Particles moving very fast

So….

• The more we heat up a sample, the faster the atoms move.

• What kind of energy comes from particles that are moving?

KINETIC ENERGY

• Kinetic energy is the energy of motion.

• The faster the atoms move, the more energy they have and vice versa.

• What are these particles doing to the thermometer?

• They are colliding with it and giving it their energy.

Kinetic Energy & Thermometers

• The more energy the particles have, the more energy they can give the thermometer bulb.

• The more energy the mercury in the bulb absorbs, the faster it’s own particles move.

• The faster it’s own particles move, the more they expand.

So what does temperature measure?

• Temperature measures the kinetic energy of the particles in a sample.

• Basically, it measures how fast the particles are moving.

• The faster they are moving, the more energy they have.

Does temperature measure TOTAL energy?

Notice both are at the same temperature but there are different amounts of water in each.

No

• Temperature does not measure total energy.

• The mercury in the bulb has no “idea” how much total water there is in the sample.

• It’s just coming into contact with whatever is around it.

Conclusion

• Temperature measures the AVERAGE kinetic energy of the particles in the sample.

• It does not conclude how many total particles there are, it just measures how much energy the particles it comes into contact with are giving it.