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Transcript
What’s the Matter With You? August 7th and 8th, 2007 Unit: Chemistry Topic: Matter What is an Atom? The smallest unit of matter An atom is does have smaller components (electrons, protons, neutrons, etc). An atom, however, is the smallest particle of an element that still has the chemical properties of that element. Scientists have found 115 types of atoms so far, and new ones are still being found! How many types of atoms can you name? (H, C, Au, etc.)? Each type has its own set of properties: color, taste, texture, and different ways it reacts with other types of atoms What is Matter? Anything that has mass and occupies space. Matter has many forms such as liquid, solid, and gas What is Chemistry? Chemistry is the “science of matter” Chemistry is the study of materials and how they behave under different conditions Chemistry involves all your sense: seeing, hearing, feeling, tasting, and smelling Chemistry is a springboard into other fields of science. o The chemistry of atoms is necessary for explaining the concepts of electricity and magnetism in physics o The chemistry of molecules is necessary for explaining the concepts of photosynthesis and genetics in biology Chemistry started with the alchemists who wanted to turn other metals into gold What’s the Matter With You? Team members’ names: Experiment #1: No Room (From VanCleave’s Chemistry for Every Kid) Background: Some matter you can see and some you can’t, but all matter takes up space. This experiment shows us this fact. Question: Is there any matter inside of an “empty” coke bottle? Procedure: Hold on to the top of the balloon and push the rest of the balloon inside of the bottle. Stretch the top of the balloon over the mouth of the bottle. Choose one person from the team to try to inflate the balloon by blowing into it. Throw away the used balloon. Results: What happened (one sentence)? Conclusions: Even though you can’t see it, there is matter (air molecules) inside the bottle. This matter takes up room and prevents the balloon from inflating. Experiment #2: Lose Some Mass—It’s a Gas! (From http://www.chemistry.org/portal/a/c/s/1/wondernetdisplay.html?DOC=wondernet\activities\matter\mass.html) Background: From the previous experiment we learned that one property of matter is that it takes up space (even if we can’t see the matter). Another interesting fact about matter is that it can change its state. Some of the states of matter are liquid, gas, and solid. There are special names for changing between different states of matter. Can you match the processes with the correct names? Process Name Sublimation liquid to gas Freezing solid to gas Melting gas to liquid Evaporation liquid to solid Condensation solid to liquid In this experiment we will observe different rates of evaporation for water and alcohol. Since water and alcohol have different atomic structures, they have different physical properties and evaporate at different speeds. Before we begin, let’s take a moment to consider the two chemicals we’ll be using. Take a look at the two pictures below and see if you can answer the following questions: Which one is water (H2O) and which one is isopropyl alcohol ((CH3)2CHOH)? How many different types of atoms does each molecule contain? Question: Will water or alcohol evaporate more quickly? Procedure: Dab one end of the q-tip into water and the other into the alcohol. Make a quick swipe of each liquid onto a small piece of construction paper. Blow on the lines and see which disappears first. Results: Which chemical evaporated the fastest (one sentence)? Conclusions: The alcohol evaporated more quickly than the water. Why? The attractive forces between water molecules are stronger than the attractive forces between alcohol molecules. It takes less energy for alcohol molecules to overcome these attractive forces and change to the gas state. Chemists say that the vapor pressure of alcohol is greater than the vapor pressure of water (meaning it takes less energy for alcohol to become a vapor). Experiment #3: Imploding Cans Background: In the previous experiment we learned a little about the three common states of matter. This experiment further explores the differences between the three states. Can you answer the following questions? What are common names for water in the three different states? How are the physical properties of the three states different? Is the chemical structure of water different in the different states? Which state do you think has the most empty space between molecules? Which state do you think has the least amount of empty space between molecues? (Hint: Where does ice sit on a frozen lake?) Procedure: Add two or three tablespoons of liquid water to an empty coke can. Place the can on the heater and bring the water to a boil (listen—you will hear it bubbling). Let the water boil for another 30-60 sec. The TUTOR should carefully pick up the can with tongs, invert the can over a bowl of COLD water and quickly drop it into the bowl. Results: What happened (one sentence)? Conclusions: The heating changed the liquid water into water vapor. Water vapor is less dense (i.e., has more empty space between molecules) than liquid water. When you dropped the can into cold water, the vapor condensed back into liquid water and left a partial vacuum (empty space) inside of the can. Recall from Experiment #1 that air is matter—it has mass and takes up space. The air’s mass exerts forces on the can, which is now empty and unable to counteract these forces. Hence, the can collapses! Bonus Question: What keeps you and me from imploding right now due to all this air pressure? Experiment #4: Kerplunk! (From VanCleave’s Chemistry for Every Kid) Background: This experiment explores another property of matter: inertia. Inertia is the tendency of a material not to change its motion or state of rest, and all matter exhibits inertia. Isaac Newton, a very famous scientist, stated this law of motion in the 17th century. Question: Does a penny have inertia? Procedure: Lay the index card over the mouth of the glass. Place a penny on top of the card. It should be centered over the mouth of the glass. Snap the card with your finger. Results: What happened to the penny (one sentence)? Conclusions: Before you snapped the card, the penny and card were both at rest due to their inertia. Then the card is snapped from under the stationary coin. The coin simply falls into the cup due to the force of gravity pulling the coin downwards. Experiment #5: Air Everywhere! (From http://wow.osu.edu/experiments/gases/newspaper.html) Background: In Experiment #1 we found that air, like all matter, takes up space. We will also show that air has mass in this experiment. Question: Does air have mass? Procedure: Spread the newspaper smoothly across a table. If the newspaper was folded, make sure the inside of the paper is facing up and the outside is facing the table (otherwise air gets underneath and the results are not what they need to be). Place the ruler partway underneath the paper, with one end of the ruler extending beyond the edge of the table a few inches. Bring your hand down on the end of the ruler extended beyond the table edge (you can push as hard as you like!) Results: What happened (one sentence)? Conclusions: Air has mass and gravity pulls it downward, exerting a downward force on the paper. The force of you pushing on the ruler is not enough to counter this downward force, so the air pressure holds the newspaper to the table.