Structure of Matter
All substances on earth are made of different combinations of the 109 known elements. Oxygen (O), gold (Au) and Iron (Fe) are examples of elements. Notice that each element is identified by an abbreviation (H = hydrogen, Na = sodium, K = potassium)
1. Element = ______
______
Approximately 25 elements occur in living things. Four of these elements make up 96% of the living matter in your body.
2. Main elements of life: ______
The word atom comes from the Greek word atomos meaning “indivisible.”
3. Atom= ______
______
Protons: _____
Neutrons: _____
Electrons: _____
Sometimes atoms can lose their electrons or gain extra electrons. This changes the electrical charge of the atom…it is now called an ion.
4. Ion = ______
The atoms of most elements interact with one another forming molecules. Molecules can be made up of atoms of the same element (O2) or of different elements (CO2). When atoms form molecules, they either share or donate electrons creating a bond. Bonds contain ENERGY.
5. Bond = ______
______
6. Molecule = ______
______
* Important biological molecules: ______
A subscript shows the number of atoms present in the molecule. If there is a single capital letter or a capital and lowercase without a subscript, it means that there is only one atom of that element in the molecule.
Name / Use / Formula / # AtomsCalcium carbonate / Limestone / CaCO3
Structure of Matter Reinforcement
Complete the following WITHOUT using your notes…
There are 109 known ______which are the smallest parts of matter. The four elements that make up 96% of the human body are ______. The smallest part of an element is an ______. A ______holds two or more atoms together forming a ______. Bonds contain ______. The subatomic particle that is responsible for bond formation is the ______. If an atom gains an electron, it will have a ______charge. If an atom loses an electron, it will have a ______charge. Charged atoms are called ______.
Water: A Polar Molecule
POLAR molecules are ______charged.
· They form ______bonds, which are ______bonds, with other polar molecules.
· Bonds exist between two ______rather than between two atoms.
· Hydrogen bonds hold molecular shape (enzymes, protein and DNA)
· The most common polar molecule is ______. The oxygen end has a slightly negative charge and the hydrogen end has a slightly positive charge.
· Opposite charges attract.
· ONLINE ACTIVITY 4.4: Describe how two water molecules can be compared to two magnets. ______
______
______
· Other polar molecules include ______
NONPOLAR molecules are ______charged and do NOT form bonds with polar molecules…. only with other nonpolar molecules.
The Behavior of Water
1. ______= The tendency of water molecules to form hydrogen bonds with other water molecules.
2. ______= The tendency of water molecules to form hydrogen bonds with other polar molecules.
3. Water also exhibits ______which results from both cohesion and adhesion working together creating hydrogen bonds on the surface of any body of water.
4. Cohesion and adhesion also work together to direct water up the stem of plants against gravity. This phenomenon is called ______.
The Unique Properties of Water
Chapter 4.4
1. What percentage of your cells consist of water? ______
2. What two qualities of water allow it to do “special things?”
______
TEMPERATURE MODERATION
3. When a substance is heated, how are its molecules affected?
______
4. When water is heated, some of the heat energy is used to ______. As are result, the water undergoes ______temperature change than other substances.
5. How does this property affect land areas near oceans and lakes?
______
6. When you sweat, water moderates temperature through ______.
7. Heat from the ______is used to break ______bonds of water, releasing water molecules into the air. Since the heat is being taken away from the skin, the result is cooling.
LOW DENSITY OF ICE
8. In most substances, solids are ______dense than liquids.
9. In water, the solid form (ice) is ______dense than liquid water because in ice the hydrogen bonds keep the molecules ______. This causes ice to ______.
10. How is this property of water important to living things?
______
WATER’S ABILITY TO DISSOLVE OTHER SUBSTANCES
11. Water is a good solvent because it can ______
12. Water is the main solvent inside all ______, in ______and in ______.
13. This property of water allows chemical reactions to take place in living things!
All living things are dependent on water. Inside your body, your cells are surrounded by a fluid that is mostly water, and your cells themselves are 70 to 95 percent water. The abundance of water is a major reason Earth can support life. Water is so common that it is easy to overlook its extraordinary properties, which are linked to the structure and interactions of its molecules.
Water's Life-Supporting Properties
The polar nature of water and the effects of hydrogen bonding explain most of water's unique properties. These properties include cohesion and adhesion, temperature moderation, the lower density of ice compared to liquid water, and water's ability to dissolve other substances.
Temperature Moderation If you have ever burned your finger on a metal pot while waiting for the water in it to boil, you know that water heats up much more slowly than metal. In fact, because of hydrogen bonding, water has a better ability to resist temperature change than most other substances.
When you heat a substance—such as a metal pan or water—its temperature rises because its molecules move faster. But in water, some of the thermal energy that is absorbed goes to break hydrogen bonds. That doesn't happen in the metal pan, which has no hydrogen bonds. As a result, the water absorbs the same amount of thermal energy but undergoes less temperature change than the metal. Conversely, when you cool a substance, the molecules slow and the temperature drops. But as water cools, it forms hydrogen bonds. This releases thermal energy in the form of heat, so there is less of a drop in temperature than in metal.
One result of this property is that it causes oceans and large lakes to moderate the temperatures of nearby land areas. In other words, coastal areas generally have less extreme temperatures than inland areas. For example, a large lake can store a huge amount of thermal energy from the sun during the day. Then at night, heat given off by the gradually cooling water moderates the otherwise more rapid cooling of the air and land.
Water also moderates temperature through evaporation, such as when you sweat. Evaporation occurs when molecules at the surface of a liquid escape to the air. As water molecules evaporate, the remaining liquid becomes cooler. The process of evaporation requires thermal energy to break hydrogen bonds and release water molecules into the air. In sweating, this energy is absorbed from the skin, cooling the body.
Low Density of Ice Density is the amount of matter in a given volume. A high-density substance is more tightly "packed" than a low-density substance. In most substances, the solid state is more dense than the liquid state. Water is just the opposite—its solid form (ice) is less dense than the cold liquid form. Once again, hydrogen bonds are the reason.
Every water molecule in ice forms four long-lasting hydrogen bonds with neighboring water molecules, which keep the molecules spaced in a regular pattern. Because the molecules in liquid water are moving faster than those in ice, there are fewer and more short-lived hydrogen bonds between molecules. The liquid water molecules can fit more closely together than the molecules in ice. Since substances of lesser density float in substances of greater density, ice floats in liquid water.
How is the fact that ice floats important to living things? If ice sank, it would form on the bottom of a body of water as the water was cooling. Ponds and lakes would freeze from the bottom up, trapping the fish and other organisms in a shrinking layer of water without access to the nutrients from the muddy bottom. Instead, when a deep body of water cools, the floating ice insulates the liquid water below, allowing life to persist under the frozen surface.
Water's Ability to Dissolve Other Substances When you stir table salt into a glass of water, you are forming a solution, a uniform mixture of two or more substances. The substance that dissolves the other substance and is present in the greater amount is the solvent (in this case, water). The substance that is dissolved and is present in a lesser amount is the solute (in this case, salt). When water is the solvent, the result is called an aqueous solution (from the Latin word aqua, "water").
Water is the main solvent inside all cells, in blood, and in plant sap. Water dissolves an enormous variety of solutes necessary for life. Water dissolves table salt (sodium chloride). The positive sodium ions at the surface of a sodium chloride crystal attract the oxygen ends of the water molecules. The negative chloride ions attract the hydrogen ends of the water molecules. As a result, water molecules surround each ion, breaking the salt crystal apart in the process.
Water can also dissolve many nonionic compounds, such as sugars. The structures of sugar molecules include polar areas where electrons are shared unevenly between atoms. These areas of slight electric charge attract the polar ends of water molecules. Water molecules cling to these charged regions and separate the sugar molecules from one another.
Exploring the Properties of Water
Name: ______/ 25 points
Water is a very important molecule to living things. In this series of concise observations, we will investigate the properties of water that allow it to behave in unique ways.
OBSERVATION A: Water on a Penny (4 pts)
1. Using a dropper, add drops of water to a clean, dry penny. Draw the shape of the water on the penny after one drop, when the penny is about half full, and just before it overflows. Count how many drops of water the penny held until it overflowed. Record that number here: ______
2. Explain your observations using the terms cohesion, adhesion, polar and hydrogen bonds
______
______
______
______
OBSERVATION B: Water on a Penny with Detergent (2 pts)
1. With your finger, spread one small drop of liquid soap on the surface of a clean, dry penny.
2. Add one drop of water at a time, counting the drops. Notice how the shape of the drops differs from part A. Record the number of drops the penny held before overflowing here: ______
3. Were you able to add more or less than on the penny without soap? MORE / LESS
4. State whether soap is polar or nonpolar based on your observations. Explain.
______
______
______
OBSERVATION C: Drop Shape on Glass and Wax Paper (3 pts)
1. Place several drops of water on a piece of wax paper. Move the paper and notice how the water moves. Place several drops of water on a glass slide. Move the slide and notice how the water moves. Which substance, wax or glass, is polar? Which is non-polar? How can you tell?
______
______
OBSERVATION D: Capillary Action (5 pts)
1. Place a large dot of marker ink about 1 inch from the bottom of a piece of chromatography paper and let it dry completely.
2. Put approximately 1 inch of water in a small graduated cylinder.
3. Place the strip of paper in the cylinder so that the bottom end is immersed in water and the drop of ink is just above the surface of the water. Fold the paper over the top of the cylinder. Put this aside until the water reaches the top of the paper.
4. Describe what happened. ______
______
5. Is paper polar or nonpolar? Explain. ______
______
6. Is ink polar or nonpolar? Explain. ______
______
7. Water shows ______as it forms hydrogen bonds with the paper and shows ______as it forms hydrogen bonds with other water molecules.
8. What overall process is occurring? ______
OBSERVATION E: Water and Oil (3 pts)
1. Observe the beaker of water and oil that has already been set up for you.
2. Which is less dense? ______
3. Explain the mechanism that causes water molecules and oil molecules to separate from one another including the following terms: polar, nonpolar, hydrogen bond
______
______
OBSERVATION F: The Floating Needle (8 pts)
1. Fill a glass Petri dish with water. Try to float a needle on top. Describe what happens.
2. Coat the needle with Vaseline thoroughly. Now try it again – place it gently on the water’s surface.
3. Two processes help the needle float.
a. Vaseline is ______and water is ______. What is the result?
______
b. Water sticks to itself through ______bonds in a process called ______. Water sticks to the sides of the glass by ______bonds in a process called ______.