Temperature There are three different scales for temperature: Fahrenheit, Celsius, and Kelvin. Fahrenheit and Celsius are the two most commonly used scales.

Fahrenheit Water freezes at 32 degrees and boils at 212 degrees. There are 180 degrees between boiling and freezing.

Celsius Water freezes at 0 degrees and boils at 100 degrees. There are 100 degrees between boiling and freezing.

T F = (9/5)T C + 32 T C = (5/9)(T F -32) What would you wear if it was 30 degrees Celsius outside? What would you wear if it was 30 degrees Fahrenheit outside?

We can all tell whether it is warm or cold out but why is this not an accurate way to measure temperature? We can use a thermometer to get an accurate measurement of what the temperature is.

Thermometer: an instrument that measure temperature. What happens to the volume of mater when it gets hot? What happens to the volume of mater when it gets cold?

A thermometer uses the properties of expansion and contraction to measure temperature. Does a thermometer measure heat? NO!

A temperature is a measure of the average kinetic energy of an individual atom.

The hotter something is, the more the atoms will bounce around, stretch and bend these springs.

Atoms are constantly in motion. When anything is moving, it has kinetic energy. In a solid, the atoms act like they are connected to each other by imaginary springs.

Why does a baseball not get hotter when you throw it? The baseball is a closed system. When you throw a baseball, the atoms do not move or stretch the imaginary springs any more or less.

These imaginary springs need to stretch and bend more in order for something to become hotter. Intermolecular forces: The forces that attract molecules together when they get really close to each other. (the imaginary springs)

The Phase of Matter There are 4 phases of matter: solid, liquid, gas, and plasma As an object gets warmer, it will change its phase.

Solid: A phase of matter that holds its volume and shape and does not flow. – The atoms in a solid do still vibrate but do not move far from their position. – Think of the atoms as if they are held together by stiff springs.

Liquid: A phase of matter that holds its volume but can change its shape and flow. The atoms in a liquid are not as restricted. They still stay close to each other but they have more room to vibrate. Think of the atoms as if they were held together by a rubber band.

Gas: A phase of matter that flows and can expand and contract to fit any container. The atoms in a gas are not connected to each other in any way. The atoms are free to move as close or far apart from each other as they can. Think of the atoms as not having anything connecting them at all.

Plasma: An ionized gas phase of matter. – Examples of plasma include stars, lightning and neon-type lights. – Plasma is when the atoms are moving around so much that the electrons actually separate from the protons. – It takes a temperature of 10,000 degrees Celsius or warmer to get plasma.

Intermolecular forces and the kinetic energy of temperature are always competing against each other. In a solid, the intermolecular force is stronger than the kinetic energy.

In a gas, the kinetic energy is stronger than the intermolecular force. A liquid is somewhere in between.

Melting point: The temperature at which a solid will change to a liquid. Freezing point: The temperature at which liquid will change into a solid. Is the melting point the same as the freezing point?

Boiling point: The point at which a liquid turns into a gas. The bubbles occur when the gas forms near the bottom of the liquid.

Changing Phases Something strange occurs when it melts. Ice, for example will continue to rise in temperature until it reaches 0 degrees Celsius. Once this temperature is reached, the ice starts to melt but the temperature will not change until all of the ice is melted.

Absolute Zero: The point at which the molecules have so little kinetic energy they can not get any colder. Absolute zero is -273 degrees Celsius.

Absolute zero is 0 Kelvin (note that I did not say degrees) To convert to Kelvin, as 273 to the temperate in Celsius: K = C + 273

Kelvin is a useful unit in science because it is the only scale that is a measurement related to the kinetic energy. A comfortable room temperature is usually 293 Kelvin.