Unit 3 Review Podcast

In this post I have provided both an audio and written version of the review for the unit 3 test. The podcast provides information on what you should understand in order to be successful on the test. Please review any of the resources found here, and check your understanding by reviewing the podcast found below.


For those students who would prefer to look at a list, here is a list of topics:

  • States of matter
  • Physical vs. chemical properties
  • Intensive vs. extensive physical properties
  • Law of conservation of mass
  • Heterogenous vs. homogenous mixtures
  • Separating mixtures
  • Elements vs. compounds
  • Law of Definite Proportions
  • Law of Multiple Proportions

I still highly suggest you listen to the podcast and use the list as a way to check off topics you have a strong understanding of. As mentioned above, additional resources are available on the unit 3 page.

At the end of the podcast, I offer you one of my own test taking tips. I have found an additional “Top 10 Test-Taking Tips” that can be valuable information for you.

  1. Have a positive attitude
  2. Make a plan
  3. Don’t wait till the night before
  4. Be prepared the morning of the test
  5. Understand how the test works
  6. Manage your time
  7. If your stuck, circle it and move on
  8. MC – process of elimination
  9. Make sure your writing is legible or bubbles are filled in completely
  10. Review questions!

You can find the full article here, along with additional resources about being successful on tests.


  • 25 questions
  • Each question is worth 2 points
  • You will have the whole class period to take the test

*Test details have also been covered in class and are listed in the class syllabus.

If you missed any questions, you will have the opportunity to rework them. This class is about mastering chemistry, therefore you will have the opportunity to submit a new answer and earn half the point back by providing either new work or writing an explanation.

Please feel free to email me with any questions.







Elements vs. Compounds

Hydrogen is estimated to make up approximately 75% of the mass of the universe. Hydrogen is classified as an element and is among the 90 elements that occur naturally on Earth. An element is a pure substance that cannot be separated into simpler substances by chemical or physical processes. However, we know from the Periodic Table of Elements that there are more than 90 elements. The remainder of the elements have been made by scientists and are not known to exist naturally on Earth.

Many elements on the periodic table you have probably heard of – iron, gold, oxygen, carbon, tin, copper, etc. Each of these elements will have a unique chemical name and symbol, which can be found on the periodic table.

In contrast, a compound is made up of two or more different elements that are chemically combined. That is, they cannot be separated by physical means. Table salt’s chemical name is Sodium Chloride, or NaCl. This compound is one part sodium and one part chlorine – together they are salt. You cannot physically separate the sodium from the chloride because they have been chemically combined. Another common compound is water, or H2O. Water consists of two parts hydrogen and one part oxygen.

Can you think of some other common compounds used in daily life?

Mercury – Physical or Chemical Change?

It’s possible that you may have heard of mercury poisoning before. Often times people associate mercury poisoning with either mercury in a thermometer or mercury that bio-accumulates in fish. The source of mercury in fish is methyl mercury. Mercury has also been used in a variety of products throughout our history, including dental fillings.

Some fish are found to have very high levels of methyl mercury in their system:

Read the mercury guide article about the different sources of mercury poisoning. It is also available in Spanish. 

What happens when mercury is consumed?

Physical changes are changes that alters a substance without changing its composition.

Chemical changes is a process where one or more substances change into a new substance, which will have different compositions and different properties.

Based on these two readings and the definitions above, would you suspect mercury poisoning in humans to be the result of a physical or chemical change?

What are some of the side effects of mercury poisoning?



States of Matter

As you are sitting at your desk drinking a glass of water, you are in contact with 3 different states of matter. Can you name them?

The air you are breathing is in the state of gas, the chair you are sitting on is a solid, and the water you are drinking is a liquid. Did you know there are two other states of matter? For more information on the five phases, click HERE.

Each of these states of matter can be distinguished by putting them in a container.


  • Fixed/definite shape and volume
  • Particles are tightly packed


  • Constant volume
  • Takes the shape of the container
  • Particles are able to move


  • Flows to fill container
  • Fills entire volume of container
  • Particles are far apart

The following video shows H2O in its different states:

OR, the following video from Khan Academy explains states of matter in greater depth – advanced.


For more resources on the states of matter, visit unit 3.