Freezing/Melting and Boiling Points

Spacing of Molecules in a Solid, Liquid, & Gas

• Use this link http://www.chem.purdue.edu/gchelp/liquids/character.html

Freezing/Melting Point• What is freezing point?• It is the temperature at which a liquid

becomes a solid

Freezing/Melting Point• What is melting point?• It is the temperature at which a solid

becomes a liquid

Freezing/Melting Point

• What is the unit of measurement that scientists use for temperature?

• Celsius• What is the temperature at which a

WATER (liquid) becomes a solid (ice or snow)?

Freezing/Melting Point

• What is the temperature at which a WATER (liquid) becomes a solid (ice or snow)?

• Use the thermometer to measure the temperature

Freezing/Melting Point

• What is the temperature at which a WATER (liquid) becomes a solid (ice or snow)?

• You should have gotten a temperature right around 0o degrees Celsius

• If you did not get 0o - your thermometer may not be very accurate

Freezing/Melting Point

• If the temperature warms up 1 degree above 0o Celsius – what happens?

• The ice or snow will melt• Or change from a solid to a liquid

Freezing Point

• On your handout, use a marker to color in the temperature at which water freezes or becomes a solid (ice or snow) on the “Freezing Point” thermometer

Water freezes at ____ degrees Celsius

Water is a liquid that changes to a solid when it freezes.

Boiling Point

• What is a boiling point?• It is the temperature at which a liquid

becomes a gas.

Gas

Boiling Point

• What is the boiling point of water?• Does water continue to get hotter the longer

you let it boil?• Let’s try it & see

Boiling Point

• At what temperature did the water boil?• 100o Celsius• Did the water continue to get hotter the longer you

let it boil?• No• Once the water boils, it will not get any hotter – it

will continue to boil until it all the liquid changes into a gas

Boiling Point

• On your handout, use a marker to color in the temperature at which water (a liquid) boils or becomes a gas on the “Boiling Point” thermometer

Water boils at ____ degrees Celsius

Water is a liquid that changes to a gas when it boils.

Heating Chocolate

• What happens to chocolate when we heat it?

• Is the chocolate chip a solid or liquid?

• It’s a solid

• Place one chip on your spoon and hold it over the candle for about 45 seconds

• Use your tooth pick to poke it

Heating Chocolate

• What happens to chocolate when we heat it?

• Is the chocolate chip a solid or liquid AFTER heating?

• It’s turning into a liquid

• Did it boil or change into a gas?

• NO

5.7D - Science concepts (Objective 3 - Physical Sciences).

The student knows that matter has physical properties.

The student is expected to:

observe and measure characteristic properties of substances that remain constant such as boiling points and melting points.

Let’s try some practice TAKS questions

Water boils at 100o C

Does it change into a gas?

Yep!

Yep!

Yep!