Biology
Standard 2: Objective 1
Title: Wonderful Water
Description: In this activity students will be introduced to some of the important properties of water and some of the key vocabulary associated with water. This can be a group or an individual activity.
Materials needed: student sheets, textbook
Prior to Assessment: No background information is necessary.
Time Needed: 1 class period
Teacher Procedures:
1. Write the following words on the board: solvent, solute, adhesion, density, cohesion, polarity. Have the students fill them in the center of the boxes on their student sheets.
2. Give students time to research the meaning of each word and fill in the charts.
3. Handout the reading selection and explain to student that they need to fill in the missing words from the vocabulary words they just defined.
Definitions:
1. Polarity: a molecule with a positively charged portion and a negatively charged portion, overall the molecule is still neutral
2 adhesion is attraction between molecules that are different,
3. cohesion is the attraction between molecules that are the same.
4. density is the amount of matter in a given amount of space
5. solvent-a substance in which other substances dissolve
6. solute-a substance that dissolves in another substance.
Student Page Name__________________________________________
Title: Wonderful Water
Purpose: To build vocabulary needed to understand a reading selection about water.
Materials: textbook
Procedures:
1. Fill in the circle in each box with one of the following words: polarity, adhesion, cohesion, density, solvent, and solute.
2. Use your book to complete each box for the word in the circle.
3. Use this knowledge to fill in the blanks on the Water Reading Selection.
Water Reading
Water is an amazing substance and an important reason why there is life on Earth. Without water, our planet would resemble the other “dead” planets in our solar system. The properties of water account for its ability to be involved in all living systems. In this reading you will discover how the properties of water affect what water can do.
The property of ___________ describes how water molecules are neutral as a whole but one end of the water molecule tends to have a positive charge while the other has a negative charge. Each end of a water molecule is attracted to the opposite charged end of another water molecule. Consequently, water's _________ is responsible for the "stickiness" or the ____________ between the molecules.
Cohesion of water allows water to move uphill in small spaces. Water will move up the fibers of a plant because the _____________ strength of water molecules to the plant fiber is greater than the cohesion strength between the water molecules. This force helps plants get the water they need to survive. In addition, it moves water upwards in soil. __________ of water molecules causes surface tension, water's invisible skin which allows water striders to walk on water.
Water is often described as a ________________because it is able to dissolve many other substances. Water is an important part of all body fluids because it contains dissolved in it many _______________ such as gases, wastes and nutrients. These substances are moved around the body in a water solution.
Polarity is also related to solubility. Polar substances can dissolve other __________ substances. Non-polar substances dissolve other non-polar substances. Polar substances and non-polar substances, however, do not mix. In a cell, the cell membrane is non-polar and does not dissolve in water. Cells could not exist with water in or around them if the cell membrane dissolved in water.
Another property of water that affects living things in lakes and oceans is the unique change in _________ of water during phase changes. The __________ of most substances increases when a liquid becomes a solid. This is not so for water: Solid water is actually less _________ than liquid water. It is for this reason that ice floats. Can you imagine a world where ice sank? Lakes would freeze from the bottom up, killing many fish. Frozen water in the polar regions would sink and change the ocean levels. The fact that ice floats is essential for the survival of many aquatic ecosystems and ultimately life on Earth
As you can see, water has many special properties that make its role in nature unique. One of water's special characteristics is the "stickiness" or ___________between water molecules. This property of _______________ helps water to move through plant fibers. Water able to dissolve many substances. In fact, water is considered the "universal ___________". Contrary to other substances, water is less ______ in its solid form than in its liquid form, hence a solid that floats! Water is the only substance that occurs naturally in all three states on Earth.