The Properties of Water Worksheet PDF

The Properties of Water A water molecule is made up of two hydrogen atoms bonded to an oxygen atom. Each end of a water molecule has a slight electric charge. A molecule that has electrically charged areas is called a polar molecule. This uneven distribution of charges across a molecule making...

The Properties of Water A water molecule is made up of two hydrogen atoms bonded to an oxygen atom. Each end of a water molecule has a slight electric charge. A molecule that has electrically charged areas is called a polar molecule. This uneven distribution of charges across a molecule making one end positive (H) and the other negative (O) is called polarity. The positive hydrogen ends of one water molecule attract the negative oxygen ends of nearby water molecules causing them to stick together like weak magnets. This attraction causes water molecules to form temporary bonds that break easily. They are called hydrogen bonds. Many of water's unusual properties occur because of the attraction among its polar molecules. The properties of water include cohesion, adhesion, capillary action, surface tension, the ability to dissolve many substances, and high specific heat. The tendency for water molecules to form weak bonds and stick to each other is called cohesion. Because of cohesion, water molecules remain joined together as they move within or between the cells of organisms. A special example of cohesion is surface tension. Surface tension is a force that acts on the particles at the surface of a liquid. Surface tension is the tightness across the surface of water that is caused by polar molecules pulling on each other. In liquid water, each water molecule is pulled in all directions by other water molecules. At the surface of the water, however, the attractive force of other water molecules pulls only downward and sideways. This force causes molecules at the surface to be held more tightly together, forming a kind of skin at the water's surface. Small insects, such as water striders, can walk on water by taking advantage of this surface tension. It is what causes raindrops to form round beads when they fall onto a car windshield. Water molecules are not attracted only to each other. Adhesion is the tendency of water to stick to other substances. You see adhesion at work when you add water to a graduated cylinder. At the surface, water creeps up slightly at the sides of the cylinder, forming a curved surface called a meniscus. Adhesion allows water to stick to the sides of blood vessels or to the vascular tubes in plants. Both adhesion and cohesion allow water to move in one continuous column from a plant's roots to its leaves. This upward movement called capillary action as seen in the test tubes in the picture is the result of both adhesion to the sides of the glass and cohesion of the water molecules to each other. Capillary action is the combined force of attraction among water molecules and with the molecules of surrounding materials causing a liquid to climb upward against the force of gravity. It allows water to move through materials with pores inside. It also causes water molecules to cling to the fibers of material like paper and cloth. Capillary action along particular cloth fibers pulls water away from your skin keeping you dry. A solution is a mixture that forms when one substance dissolves another. The substance that does the dissolving is called the solvent. Water is called the universal solvent because it can dissolve more substances than any other known substance. The main property of water that makes it such a good solvent is its polarity. The charged ends of the water molecule attract the molecules of other polar substances. (like dissolves like) It can dissolve substances like sugar, bleach, salt. It can dissolve gases such as carbon dioxide and oxygen. Dissolving salt is an example. As the negative side of water forms bonds with the Na+ and the positive side is attracted to Cl- ions in a crystal of salt (NaCl), it pulls these ions into solution, the crystal dissolves. The ability of water to dissolve many substances allows water to deliver essential nutrients to cells in plants, animals, and other organisms. Water dissolves nutrients in our food. It does not dissolve nonpolar substances like oil and wax. They don’t like water and are called hydrophobic. (fear water) Specific heat is the amount of heat needed to increase the temperature of 1 kg of a substance by 1°C. Compared to other substances, water requires a lot of heat to increase its temperature. The unit of specific heat is joule per kilogram per degree Celsius (J/kg 0G). The specific heat of water is very high-4,184 J/kg °C. Therefore, water takes a long time to heat up or cool down. Water has a high specific heat because of the strong attraction among water molecules (cohesion). This property of water allows lakes, streams, and ocean ecosystems to maintain stable temperatures, even if air temperatures change dramatically. So that the air over water is cooler than the air over land on hot days. The high specific heat of water also helps your body to maintain a constant internal environment Name_____________________________ Properties of Water Write the definition of each key term. polarity: ___________________________________________________________________________ ___________________________________________________________________________________ cohesion: __________________________________________________________________________ ___________________________________________________________________________________ adhesion: ___________________________________________________________________________ ___________________________________________________________________________________ capillary action: ______________________________________________________________________ ___________________________________________________________________________________ surface tension: ______________________________________________________________________ ___________________________________________________________________________________ specific heat: ________________________________________________________________________ ___________________________________________________________________________________ hydrogen bond: ______________________________________________________________________ ____________________________________________________________________________________ 1. Circle the letter of each sentence that is true about water's structure. a. Water is made up of atoms bonded to form molecules. b. Water contains half as many hydrogen atoms as oxygen atoms. c. Water molecules tend to push away from each other. d. The chemical formula for water is H20. 2. One side of the water molecule has a positive charge, while the other side has a negative charge. What do the charges indicate about the molecule? a. Water is a polar molecule. c. Water is an ionic compound. b. Water is a nonpolar molecule. d. Water is an ion. 3. Bonds that form between water molecules are called ____________________bonds. 4. True or False? Hydrogen bonds are strong and require a lot of energy to break. 5. The tendency for water molecules to stick to other water molecules is called _____________________. 6. A force that acts on the particles of a liquid at the surface is called _______________________________. 7. How does surface tension force the surface of water to curve? _____________________________________________________________________________________ _____________________________________________________________________________________ 8. The tendency for water molecules to be attracted and stick to other substances is called _______________________________. 9. Circle the letter of each sentence that is true about water's surface tension. a. It helps some insects "skate" across the surface of the water. b. It refers to the tightness across the surface of the water. c. It is caused by polar molecules repelling each other. d. It causes raindrops to form round beads. 10. What is a curved surface in a graduated cylinder called? A _____________________ 11. Circle the letter of each sentence that is true about capillary action. a. It explains how water moves against the force of gravity. b. It is due to the attraction among molecules of water and surrounding materials. c. It prevents water from moving through materials with pores. d. It causes clothing to stay dry. 12. How does capillary action allow water to climb up the sides of a straw? ______________________________________________________________________________________ ______________________________________________________________________________________ 13. A mixture that forms when one substance dissolves another is called a(n)______________________. The substance that does the dissolving is called a(n) __________________________________. 14. Why can water dissolve many substances? _________________________________________________ ___________________________________________________________________________________ 15. Circle the letter of each substance that dissolves in water. a. salt b. oil c. oxygen d. wax 16. A substance that hates, or “fears” water is called __________________________ 17. The amount of heat needed to increase the temperature of a certain mass of a substance by 1°C is its ________________________________. 18. True or False? Compared with other substances, water requires a lot of heat to increase its temperature. 19. Circle the letter of each sentence that is true about water's specific heat. a. It is due to the many attractions among water molecules. b. It makes large bodies of water heat up more quickly than nearby land. c. It makes large bodies of water cool off more slowly than nearby land. d. It leads to warmer air over land than over water on summer days. 20. How does the high specific heat of water affect your body? ______________________________________________________________________________________ ______________________________________________________________________________________ Match the terms review. _____1. cohesion a. tendency to stick to other substances _____2. capillary action b. tightness caused by the pulling of water molecules on each other _____3. adhesion c. the amount of heat needed to raise 1kg of a substance 1º _____4. polarity d. weak bonds formed between water molecules _____5. hydrogen bond e. tendency to stick to other water molecules _____6. surface tension f. uneven distribution of charges in a molecule _____7. specific heat g. tendency to climb up due to cohesion and adhesion properties of water