Explore changing temperature

As the weather starts to get cooler, here's something neat you can try at home to monitor the changes.  Make your own thermometer!

Supplies:
Empty glass soda bottle
Measuring cup
1/2 cup of water
1/2 cup of rubbing alcohol (with adult supervision)
Food coloring
Clear straw
Modeling clay
Permanent marker

How to do it:
1. Pour the water into the glass bottle.
2. Pour the rubbing alcohol into the bottle.
3. Add a few drops of food coloring and gently swirl the bottle to mix the liquid.
4. Insert the straw into the bottle.  The bottom of the straw should be in the colored water, but not touching the bottom of the bottle.
5. Secure the straw at the top of the bottle with modeling clay.  Do not cover the top of the straw.
6. Place your thermometer in the sun and wait a little while.  The liquid will rise up the straw.
7. Use the marker to to draw a line on the outside of the bottle to show where the top of the liquid is in the straw.  Write the date next to the line.
8. Use your thermometer in the same spot and at the same time each day for a week.  Each time, mark the level of the liquid and the date.
9.  You have collected data!  What does the data tell you about the temperature over the week?