Activity 7.8 (2 of 5) Student Handout (1 of 3) Atomic Theory Lab Pre Lab: Define hydrate. What is the formula of copper(ll) sulfate? _ Pre Lab -Coppet sulfate is bonded to water when in the crystal phase. This is called a hydrate. By simple heating, the water molecules are liberated from the hydrate (they evaporate). According to Proust's experimentation in the early 1800's, atoms combine in definite proportions by mass. This law can be extended to apply to molecules. In this instance, the same number of water molecules will be liber- ated from each copper sulfate molecule. The ratio of the amount of liberated water to the total mass of copper sul- fate and water should remain the same no matter what how much material is used. 1. Preliminary observations of copper (ll) sulfate pentahydrate crystals. Writing in complete sentences, record at least five qualitative observations. Make full use of available equipment including: microscope, balance, Bunsen burner. Draw two diagrams. 2. What substances from your everyday experience appear dry, but actually contain water? Work with your part- ner to compile a list of at least five substances. Give evidence to justify each claim. Materials -- • Scapula • Clay triangle • Iron ring • Burner • Balance' • Watchglass • Ring stand • Evaporating dish • Tongs • Hydrate Procedure Record all qualitative observations that seem relevant. 1. Record mass of evaporating dish and watch glass. 2. Add copper sulfate hydrate (CuS0 4 ) to an evaporating dish until it is approximately 05 em deep . Record mass of evaporating dish, watch glass and copper sulfate hydrate. Calculate the mass of the copper sulfate hydrate. Think: you need to determine the mass of the copper sulfate only - no evaporating dish . How can you do this? 3. Place the evaporating dish on the clay triangle 5--6 em above the Bunsen burner the cooler part of the flame. Then place the watch glass on the evaporating dish. Heat the copper sulfate slowly. In heating, the copper sul- fate will gradually turn very pale blue or gray. If it begins to darken, you are heating it too fast, reduce the flame . If ic.:::m Oil cool parts of the evaporating dish, heat them and they will disappear. 4. When all the copper sulfate has turned pale blue, allow evaporating dish to cool and then mass the evaporating dish and copper sulfate residue. Record. 5. Reheat evaporating dish for 3 more minutes and allow to cool. Mass dish and watch glass and record. If , masses are within .05 g, clean up your station . If not, repeat step five until the two subsequent mass readings are within .05 g of each other or time is called. 6. Obtlintheresults of the lab groups and record. Data Table Your tablewill resemble this one. You need to make one that fits all your data needs. If you need more heat- ings, record those masses too. / I : ." :. . . ' "'.:- "'i ,..<,: I · , . ' :..I :t 66', iT he Wri,e'Path II: An Advanced College Preparatory Reading and Writing Programfor High Schools", , . .:.. ." . . . . --