# Week 1 – A Penny for Your Thoughts

Early chemists were known as alchemists.  Notice that both chemistry and alchemist include “chem” in the word – the Wikipedia entry for the article Etymology of chemistry is an interesting read and helps explain the ancient global origin of the words.  The foundations of modern chemistry actually owe a lot to ancient scientists known as alchemists.  For nearly two thousand years, people in Africa, Asia, and Europe were actively engaged in alchemy: the work of turning ordinary (readily available) matter into gold and other substances perceived to be valuable.  For more on the history of alchemy, watch the Crash Course video below:

Why has gold become such a desired metal?  Civilizations throughout history have used gold as a display of wealth and power.  The desire to possess gold, especially the gold of other nations, has resulted in countless wars throughout history.  Through this lens, it makes sense that alchemists sought ways to create gold from other materials.  More gold should equal more wealth, and perhaps if there was enough gold, nations would stop trying to take gold away from each other by force.  By that logic, do you think alchemists were successful?

Penny Lab

# Week 1 – Properties of Matter

Previously, we reviewed the concept of volume as a measure of how much space a substance occupies.  For example, imagine you have an object in the shape of a cube.  From geometry, you remember that to calculate the volume of a cube, you simply need to measure the length of one side and then cube that value:

Vcube = side x side x side = side3

A cube with a side of length 2.8 cm would have a volume of:

Vcube = 2.8 cm x 2.8 cm x 2.8 cm = 21.95 cm3

If the cube has a mass of 59.27 g, we can use the mass and volume to calculate the density of the cube using the formula density = mass / volume (D=m/v).  Inserting what we know into the equation: D = 59.27 g / 21.95 cm3 =2.7 g/cm3

We know that density is an intensive property.  It can help us identify what the block is made of (assuming the block is a pure substance).

In the example above, we were tasked with calculating the volume of a cube.  There are a number of familiar geometric forms, like rectangular prisms and spheres, that have formulas for volume that should be familiar to you (click here to review).

• Question 10: A student fills an empty balloon with helium gas.  Conveniently, the helium-filled balloon is a perfect sphere!  The student measures the radius of the balloon as 10.3 cm.  Calculate the volume of the balloon.
• Question 11: Using the volume from Question 10 and the  density of helium on the list of the densities of common materials,  calculate the mass of helium gas in the balloon.

A graduated cylinder is used to most accurately measure the volume of a liquid.  A graduated cylinder is also a really useful tool for measuring the volume of an irregularly shaped solid.  We call that technique “water displacement” and the video below will explain how to do it:

Important things to note:

• Volume is unaffected by mass.  Two objects can have the same volume but different masses.
• The relationship between mass and volume is density.  Remember, density is equal to mass divided by volume.
• Volume can be measured in base units of liters or meters.  In our example of the cube, volume was measured in cubic centimeters (cm3).  In the water displacement method video, volume was measured in milliliters (mL).

Question 12: A student wants to know if her gold-colored chain is solid gold or gold-plated (another metal covered in gold).  After consulting the list of the densities of common materials, she knows the expected density of gold.  Next, she measures the mass of her chain using an electronic balance and finds it to be 2.4 grams.  What is the expected volume of the chain if it is really solid gold?

Question 13: What technique should the student use to determine the volume of her chain?

Question 14: Why does the overall size of a graduated cylinder affect how accurately we can measure volume?

# Week 1 – Measuring Matter

Our study of chemistry begins with the question: What is chemistry?  Simply stated, chemistry is the study of matter and how it can be changed.  In previous years, you learned that matter is anything that has mass and volume (takes up space).  Students often ask, “what is the difference between mass and weight?”  Mass is directly related to the number of atoms in a substance.  For example, you are made of atoms.  Your mass is the same whether you are on Earth or Mars.  However, weight is dependent on gravity.  Earth is more massive than Mars, so the force of gravity is greater.  According to an article on Space.com, the gravity of Mars is 38% that of Earth.  To figure out your weight on Mars, multiply your weight in pounds by 0.38 and that’s how much you would weigh.  For example, if you weigh 100 pounds on Earth, you would only weigh 38 pounds (100 pounds x 0.38) on Mars!

In chemistry, we will often use mass in our analysis of matter.  Certainly the chemistry of matter on Earth is very important, but so is the chemistry of matter on Mars, the Sun, and everywhere else in the Universe.  As students of science, we want our learning to apply as widely as possible!  Mass is measured in base units of grams (g).  The amount of space something takes up, called volume, is measured in base units of liters (L).  Distance is measured in base units of meters (m).

The meter is one of 7 fundamental units, called SI Units (read more about them here).  The SI unit for mass is the kilogram (kg).  The prefix kilo- means 1000, so adding kilo- to the base unit of gram means 1000 grams.  Similarly, one kilometer (km) is equal to 1000 meters, and one kiloliter (kL) is equal to 1000 liters.  Other commonly seen prefixes include milli- (1/1000) and centi- (1/100).  For example, there are 1000 millimeters (mm) in 1 meter, and 100 centimeters (cm) in 1 meter.

• Question 1: How many mm are in 1 cm?

Brain break!  Check out this inspired piece of musical art by the famed middle school science and math teacher Pete Hendley (aka KILA META):

…and we’re back.  Meters, liters, and grams are all considered extensive properties of matter.  An extensive property is specific to the amount of matter and therefore changes if the quantity of a substance changes.  Imagine you have an empty two-liter (2 L) soda bottle.  You measure out 500 mL of distilled water in a beaker and pour it carefully into the bottle, using a funnel to be sure not to spill.

• Question 2: How many liters is 500 mL?
• Question 3: After adding the 500 mL of water, what fraction of the 2 L bottle is filled with water?

Next, you measure another 250 mL of water in your beaker and carefully pour it into the bottle, increasing the volume of the water to 750 mL.  This demonstrates that when we change the amount of liquid in the bottle (the volume of liquid), the number representing the volume also changes.  Therefore, volume is an extensive property.  Great job!  Mentally pour out the water and then continue reading.

Earlier, we discussed the difference between mass and weight.  If you have a bathroom scale at home, you can measure your weight in pounds. In science, we measure mass using a balance.  Many students first learn to measure mass using a triple-beam balance.  In high school chemistry, we work with small amounts of mass and often choose to use an electronic balance which allows us to precisely measure down to the nearest tenth or hundredth of a gram.  On Earth, you can approximate your mass by taking dividing your weight in pounds by 2.2.  For example, a person weighing 154 pounds would have a mass of about 70 kilograms.  Similarly, you can calculate your approximate weight on Earth by multiplying your mass by 2.2.

• Question 4: Calculate the approximate weight (in pounds) of a German Shepherd dog with a mass of 35 kg living on Earth.
• Question 5: Imagine the 35 kg dog from Question 4 takes a rocket to Mars.  Calculate the approximate weight of the dog on Mars.
• Question 6: For the German Shepherd from questions 4 and 5, what is the mass of the dog on Mars?

Back to our experiment!  Imagine you measure out 500 g of liquid water using your electronic balance.  As before, you carefully add the water to the empty 2 L bottle using a funnel.  Next, you measure out an additional 250 g of water using the electronic balance and add that to the bottle.

• Question 7: What is the final mass of water in the 2 L bottle?
• Question 8: Is mass an intensive or extensive property?

While some properties of matter change based on the amount of matter present (extrinsic properties), others do not.  Intensive properties do not depend on the amount of matter present and therefore can be used to identify matter. Intensive properties include density, boiling point, and the color of an object.  Liquid water has a density of 1 g/mL (1 gram of water occupies a volume of 1 milliliter).  Liquid water boils at 100 degrees Celsius (212 degree Fahrenheit).  Liquid water is colorless (clear).  If you were given the 2 L bottle from the thought experiment above, but did not know the identity of the liquid inside, you could quickly determine the color and then measure the density and the boiling point.  That information taken together would help narrow down the identity of the liquid to likely be water.  However, if you measured the mass or volume of the unknown liquid, that data would not help you determine the identity of the liquid, as you can imagine an infinite number of substances with a mass of 750 g or a volume of 750 mL.

# Week 1 – Welcome to Chemistry

As you work through this week’s lesson, you will have opportunities to engage as deeply in the material as you find helpful.  There are videos, links to articles, vocabulary terms used in context, and plenty to read to expand your understanding of the world around you through the lens of chemistry.

Weekly lessons are broken up into sections, called parts.  Each part will roughly correspond to one day of work.  Some parts may be longer than others depending on the learning demands of the content.  Pace yourself accordingly.  You are welcome to complete one part each day, or do more or less depending on your needs that day.  As long as you complete the work before the next week’s learning becomes available (weekly posts become visible at 8:00 am each Monday morning), you will stay caught up!

Before you complete the assignments and take the weekly quiz, understand the resources you have available for help guide you in your learning:

• At the end of each part of the lesson, you will find a link to a Jamboard – basically a place to post digital sticky notes that will serve as a discussion board.  You are encouraged to post questions, post answers, and use the space to share ideas, support each other, and make friends.
• You will have “class time” each day to meet with your classmates and teacher in Zoom breakout rooms to discuss the learning.
• Form a study with your classmates and find a system for meeting and sharing ideas and questions that works for the group.
• And you can always email Mr. Swart with questions or for help setting up peer study groups.

We begin the year with a short week, so let’s dive in!  Click here to return to Week 1 – The Golden Penny and get started by taking the Week 1 Pre-Assessment.

# Week 1 – The Golden Penny

Welcome to our first week of the 2020-2021 school year.  The fact that you have chosen to visit this page is truly exciting!  While distance learning has inevitably changed the way we are doing school this year, my goal is to provide you with the opportunity to engage with chemistry at a level that will prepare you for advanced science coursework both in high school and beyond.

[Insert Week 1 Intro Video]