Properties of Water notes

Properties of WATER: The Structure of Water ● Like all matter, water is made up of atoms. ● Atoms attach together, or bond, to form molecules. Two hydrogen atoms bonded to an oxygen atom form a water molecule. A short way of writing this is to use the chemical formula for water, H2O. The oxygen end has a slight negative charge. The hydrogen ends have a slight positive charge. A molecule that has electrically charged areas is a polar molecule. Key Properties of Water (4) 1. Capillary Action ● The combined force of attraction among water molecules and with the molecules of surrounding materials is called capillary action. Capillary action allows water to move through materials with pores inside. You will see that the liquid rises higher inside the straw. As water molecules are attracted to the straw, they pull other water molecules up with them. ● This is also called adhesion, where the water molecule sticks to things. (absorb) 2. Surface Tension ● Surface tension is the tightness across the surface of water that is caused by the polar water molecules pulling on one another. The molecules at the surface are being pulled by the molecules next to them and below them. ● This is also called cohesion, where the water molecules stick to each other. (Remember: cohesion happens in a cloud.) 3. Universal Solvent ● A solution is a mixture that forms when one substance dissolves another. The substance that does the dissolving is called the solvent. Water dissolves so many things! Many substances dissolve in water because water is polar. The charged ends of the water molecule attract the molecules of other polar substances. Water dissolves so many substances that it is called the “universal solvent.” 4. Specific Heat ● Specific heat is the amount of heat needed to increase the temperature of a certain mass of a substance by 1°C. ● Water’s high specific heat is due to the strong attraction among water molecules. - Although the air is hot, the water offers cool relief. Water’s high specific heat keeps it from heating up as quickly as other materials. Changing State o Water is the only substance on Earth that commonly exists in all of these different states (3) Evaporation o Evaporation is the process by which molecules at the surface of a liquid absorb enough energy to change to the gaseous state. Condensation (clouds) o The process by which a gas changes to a liquid is called condensation, which then leads to precipitation. Freezing o At 0°C, the liquid water freezes, changing into solid ice Melting o When the temperature reached is above 0° C, the solid ice would melt and become liquid water – above 0°C Water moves between the liquid and gaseous states by evaporation and condensation. Water moves between the liquid and solid states by freezing and melting. Properties of Water: 1.What atoms make up a water molecule? 2 hydrogen atoms, and 1 oxygen atom = H2O 2.Describe the charge on each end of a water molecule. Hydrogen atoms are positively (+) charged, and Oxygen atoms are negatively (-) charged = polar molecule 3.Name four unusual properties that water has. Capillary action, surface tension, universal solvent, and high specific heat. 4.What are the three states in which water exists on Earth? Solid, liquid, and gas. 5.Describe how water changes state as a patch of solid ice is heated by the sun. The heat from the sun begins to melt the ice, and form a liquid. If the liquid continues to be heated, becomes a gas and evaporates. 6.Oil is a nonpolar molecule…would it dissolve in water? Why or why not?? No, oil will not dissolve in water because the oil is nonpolar, meaning it has no charged ends to attract the charge of the water molecules.