Quarter 4 Lab Practical - Melting Point Determination

7) Melting Point Test - This page will walk you through the virtual process of taking the melting point of your sample.

Figure 1.

Background: One way to determine the melting point of a chemical is to put a small sample of the sample in a glass capillary (a tiny glass tube the size of a toothpick), strap the sample to a thermometer using a tiny rubber ring, and immerse the thermometer bulb and capillary sample into oil (see picture).

Then, the oil is slowly heated and the hot oil heats up the sample.

When the sample melts, you read the temperature on the thermometer and that will tell you the melting point.

Since the sample is usually very small and hard to see, most melting point apparatuses have a magnifying lens to help you watch the sample melt from solid to liquid.

Figure 1 shows a picture of the oil bath melting point apparatus.

Figure 2 below shows a picture of the magnifying lens view of the sample in the capillary tube.

Figure 2.

Step 1) Watch this video overview on the process of setting up a oil bath capillary melting point apparatus.

Step 2) Now watch the video excerpt below which focuses in on the process of finding the melting point of an example substance, benzoic acid, which melts at 122 degrees Celsius. This will give you a virtual experience of watching the sample in the capillary tube through the magnifying window as it goes through the process of melting.

Step 3) Finally, use this online melting point simulation to determine the melting point of your unknown A, B, C, or D (note that the simulation shows the samples as brightly colored but in nature they would actually be white crytalline solids).

VIDEO book: Atoms and Matter by Tony and Erick

Click below to see a great video book two of our chemists made:

VIDEO book: Atoms and Matter by Tony and Erick

Unit 2 - Periodic Trends

We are well into Unit 2 with Periodic Trends!

In Period 4,6,7 we plotted trends for seven properties in 3-D using drinking straws! Then we analyzed the trends we observed.

We also reconstructed our own periodic table based on electron configurations and ionization behavior.

Rare Earth Metals

We are studying the structure of the periodic table and we looked at a short article on rare earth metals with the accompanying graphic from www.wealthdaily.com

This article triggered an entire class long discussion with my ELL Chemistry section! They were wondering why China had so much of those metals, and what other resources the U.S. had in comparison.

Then they wanted to talk about why so many items are manufactured in China.

Then they wanted to talk about international trade.

Then they wanted to talk about pollution and impacts of mining.

Then, going back to why so many things are manufactured in China, they wanted to talk about why there are so many people in China.

Then they wanted to talk about birth rates in US versus China versus Africa.

Then they wanted to talk about the one-child policy in China.

Then they wanted to talk about education and why Chinese students do some much better on math and science tests compared to U.S., so we talked about differences in education systems and college admissions.

Then THEY brought up why they think students in the U.S. aren't as serious about school as in other countries - they said it was perhaps because education is (almost) free here, and it's very easy to get into college here, and you don't have to decide on a "career track" until a later age compared to other countries.

I'm certain it was more meaningful for the students to come to their own conclusions about U.S. students not focusing on school than all of us well-meaning adults nagging them. 

It was a fantastic discussion. 

Those spontaneous "teachable moments" are one of my favorite parts of teaching. 

Please contribute to the discussion in the comments!

Unit 1 Wrap Up

It was great to meet so many of your families at Open House! We finished Unit 1 - Atomic Structure last week. In periods 1 and 3 we played Chemistry Baseball to review our Unit 1 Objectives!

Remember that test retakes can be done in room 120 - you must show your GOLD ticket to retake.

Speaking of gold, here's are some shots of our "marbles" lab where we modeled Rutherford's Gold-Foil Experiment to estimate the diameter of a marble by the percentage of "hits" and "misses"!

Converting Copper...and Back Again!

In Honors Chemistry we explored the idea of Conservation of Matter - the idea that atoms cannot be created or destroyed in chemical reactions.

We first heated pure copper to convert if to copper(II) oxide. Many students were surprised that the mass increased after heating!

Then we reacted the copper(II) oxide with dilute hydrochloric acid to dissolve the copper +2 ions in solution.

Finally, we reacted the blue aqueous copper +2 solution with either zinc or aluminum to retrieve the copper again!

(thanks to BigScienceNotebook for some of the images!)

Welcome Back! Introducing the Black Box...

Welcome back to school, chemists!

I know I had a great summer working on some curriculum projects and spending time with my family.

In chemistry we are diving right in to scientific experimentation and the nature of the atom. We did a class activity where we explored what was inside of a "Black Box" through indirect experimentation. We did this to model the process that scientists go through when trying to discover the nature of things that are too small to see, touch, and otherwise observe directly.

In period 3 we first tried pouring 99 mL of water into the Black Box and were very surprised when only about 85 mL of a bluish-green, odorless liquid came out!

We then tried adding 99 mL of vinegar into the Black Box and were even more surprised when 88 mL of a brighter green, vinegar-smelling liquid came out!

What do YOU think is inside the Black Box? Below are some of our drawings of what we think might be inside.

Clickers in the Classroom - Unit 10 Review

Today in Regular Chem we reviewed Unit 10 concepts using electronic clickers. After each question we saw a histogram of our class responses and used that to target our review for our test.

Equilibrium - "Hungry Hungry Hippos" style

Today we did an activity where we modeled a reversible reaction achieving equilibrium in a "closed" system. One person was the agitator representing the kinetic energy of the molecules, one person represented the "forward reaction" by putting together the beads into pairs, while another person represented the "reverse reaction" by trying to take apart the pairs at the same time! We had a great and noisy time while experiencing equilibrium at the particle level. This was a truly hands-on experience!

More Supersaturated Solutions - Per 8!

I just had to include these great pictures from period 8's supersaturated solutions lab; you can really see the crystals!

Temperature Dependent Solubility of KNO3

Today we generated a solubility curve for KNO3.

SUPERsaturated solutions!

We have been learning about the concept of solubility and different types of solutions based on the amount of solute dissolved.

Today we did a lab experiment where we created unsaturated, saturated, and supersaturated solutions!

The solute we used was sodium thiosulfate.

We first dissolved a small amount of solute in water to create an unsaturated solution, which looks somewhat clear with no undissolved solid.

Then we added more solute until the solution was saturated, as evidenced by the undissolved crystals on the bottom of the test tube.

Then we heated the mixture as the solubility of the sodium thiosulfate increases as the temperature increases.

 Finally, we cooled the test tube to reduce the solubility, and "disturbed" the solution by adding a single additional crystal of the solute. The excess solute crystallized out in a dramatic fashion!

Solutions Concept Map

We have started a concept map for Unit 10 - Solution Chemistry. This should help us relate all the vocabulary and complex ideas. We plan to continue to add to our concept map throughout the unit.

Factors Affecting Rates of Dissolution

Today we performed a small inquiry experiment to determine which factors affect the rates of dissolution. Students had to design their own procedure to test how surface area, solvent temperature, and stirring affected how much sugar dissolved in water.

The students did a great job with setting up their experimental constants such as the amount of water, amount of sugar, and method of stirring.

Be sure to ask the chemists what they discovered!

Egg in a Flask

In 8th period we put a boiled egg in a flask!

Can you explain how we got the egg into the flask?

Can you explain how we got the egg out again?

Ask your chemist!

(Thanks to this web page for the great sequential picture!)

Scan this and answer in the comments!