Lowering Freezing Points Lab:
Questions:
What are freezing points?
At what temperature does water freeze?
What is an insulator? How does it work for both heat and cold?
What is a physical property of matter?
What is a chemical change of matter?
Can we use a physical property of one substance to change matter into another physical state?
Hypothesis:
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Materials:
4 empty jars (2 per group – 1 thermometer only jar; 1 thermometer and test tube jar)
1 jar filled with salt (sodium chloride – shared between two groups)
2 glass test tubes (1 per group)
3 measuring spoons
Ice
4 thermometers
2 spoons for stirring
2 paper towels
Tape
Paper and Pencil
Procedures:
1.) Start thinking of an hypothesis.
2.) You will work in groups of two/three. Carefully unwrap glass test tubes. Have a group member take the test tube over to sink and fill ¼ way will water. Place glass test tube in center of one jar (you will need to hold this test tube in place – you will eventually put ice around test tube). Place thermometer in each jar (one thermometer only jar – Jar 1; one thermometer and test tube jar – Jar 2) with numbers facing outside - you will be lifting this out of jar and will need to quickly read this and put it back GENTLY!!
3.) Wrap a piece of paper towel around the outside of (Jar 1) AND (Jar 2) – you may need to fold the paper towel to have it fit around the jar. Put a piece of tape across the ends of paper towel to hold in place.
4.) Send one person with (Jar 1) to fill ¾ way with water and return to table and put in thermometer. Send another person with thermometer and test tube jar (Jar 2) - thermometer should be against the jar - to front of room. Fill jar ¾ way with ice. Make a “well” in the center by shifting the ice around to make a hole and gently place glass test tube in the center. Ice should surround test tube and hold it in place.
5.) Record the temperature of BOTH the (Jar 1) AND (Jar 2) in BOTH Fahrenheit and Celsius.
6.) Add one tablespoon of salt into water of (Jar 1) and stir. Record temperature (both Fahrenheit and Celsius) and your observations. Add one tablespoon of salt over the top of ice in (Jar 2). (Do not put salt in test tube.) Record temperature (both Fahrenheit and Celsius) and your observations.
7.) Repeat steps 4 until test tube is frozen in (Jar 1) and if temperature has changed in (Jar 2).
8.) Record data for both jars. Create a line graph for EACH jar.
9.) Form your own Hypothesis.
10.) Conclusion: Follow the format I have provided you in your lab books. Keep in mind to include answers to these questions and the ones above in your conclusion: What did you observe? What happened? Why? Explain. Did you witness a physical reaction or a chemical reaction? What is the difference? How do you know?