AP LAB: Identifying Types of Substances

Transcription

1 AP LAB: Identifying Types of Substances In this lab you will have 5 different types of substances: polar covalent, nonpolar covalent, metallic, ionic and network covalent. Each substance can be categorized based on properties such as melting point and conductivity. Use your notes and Chapter 9 for further information. Equipment: electrical conductivity: light device, teaspoon, glass petri dish, watch glass, water melting point: glass petri dish, hot plate solubility: assay plate, oil, water crystal structure: magnifying glass Procedure: 1. Electrical conductivity: place a small amount of each sample onto the glass petri dish, test with the light device and record your results. Split your samples into two halves for Step 4; one to test with water, the other with oil. Test the part you dissolve in water with the light device, as well. 2. Crystal structure: observe your samples using the magnifying class. Look for signs of crystal structure. Record your results. 3. Solubility: add a drop or two of oil and with a drop or two of water to the samples on the petri dish. (KEEP THEM SEPARATE). Record your results. 4. Melting point: place a clean petri dish of the substances onto the hotplate, set at medium. Observe and record the order in which your substances melt. Record your results; 1 should indicate the fastest melting substance. Some substances may not melt and/or only partially melt. Make your best estimates for all substances. Table 1. Data Sample Electr. Conduct. dry wet Crystal Structure Melting Solubility Point water oil Other Observations Type of Substance Lab Questions: 1. Explain fully why an ionic substances is not electrically conductive as a solid but conducts well when dissolved in water.

2 2. Why do we test for solubility with both water and oil? 3. What is is about the structure of a network covalent substance that does not allow it to be malleable? How does this affect its other properties such as conductiv ity and solubility? 4. What allows a metal to be malleable? (describe what happens inside each substance when subjected to bending) Again, how does this affect other properties of metallic substances? 5. What is it about the structure of a molecular nonpolar substance, such as hydrogen, H 2, that gives it a low melting point? What evidence is there that H 2 has a low melting point?

3 6. Identify the likely type of substance for each of the following: Mg, I 2, KBr, In, H 2 O, CH 4, CH 3 Br, CH 3 NH 2. Include in your answer both propery-based information AND mathematically-based information. Explain each answer. 7. Why do ionic substances tend to dissolve well in water? Describe the process of solvation.

4 8. Substance X is tested and found to have a boiling point of 278 o C. It is soluble in water, but not in oil. When dissolved in water, it will conduct electricity, but it will not conduct electricity in its solid form. What type of substance is it most likely to be AND what other properties is it likely to have? Explain your answer fully. 9. Substance Y has a melting point of o C, it will not dissolve in water, but will dissolve in oil. Based on just these properties, what type of substance is it likely to be AND what other properties is it likely to have? Explain fully Substance Z will not dissolve in either water or oil. It does not conduct heat or electricity well and it shatters when subjected to extreme twisting. What kind of melting point is it likely to have? What kind of substance is it most likely? What are some other likely properties of Substance Z? Explain your answers fully.

5 MAKE UP LAB: Identifying Types of Substances In this lab you will have 5 different types of substances: polar covalent, nonpolar covalent, metallic, ionic and network covalent. Each substance can be categorized based on properties such as melting point and conductivity. Use your notes and Chapter 8 for further information. Equipment: electrical conductivity: light device, teaspoon, glass petri dish, watch glass, water solubility: assay plate, oil, water crystal structure: magnifying glass melting point: glass petri dish, hot plate Procedure: 1. Electrical conductivity: place a small amount of each sample onto the glass petri dish, test with the light device and record your results. Split your samples into two halves for Step 4; one to test with water, the other with oil. Test the part you dissolve in water with the light device, as well. 2. Crystal structure: observe your samples using the magnifying class. Look for signs of crystal structure. Record your results. 3. Solubility: add a drop or two of oil and with a drop or two of water to the samples on the petri dish. (KEEP THEM SEPARATE). Record your results. 4. Melting point: place a clean, glass petri dish of the substances onto the hotplate, set at medium. Observe and record the order in which your substances melt. Record your results; 1 should indicate the fastest melting substance. Some substances may not melt and/or only partially melt. Make your best estimates for all substances. --make up lab: fill in the chart below based on what SHOULD happen; depending upon what kind of substance each is Table 1. Data Sample Electr. Conduct. dry wet Crystal Structure Melting Solubility Point water oil Other Observations Type of Substance C 60 CaCl 2 Pd CH 3 Br H 2 H 2 S Lab Questions: 1. Explain fully why an ionic substances is not electrically conductive as a solid but conducts well when dissolved in water.

6 2. Why do we test for solubility with both water and oil? 3. What is is about the structure of a network covalent substance that does not allow it to be malleable? How does this affect its other properties such as conductiv ity and solubility? 4. What allows a metal to be malleable? (describe what happens inside each substance when subjected to bending) Again, how does this affect other properties of metallic substances? 5. What is it about the structure of a molecular nonpolar substance, such as hydrogen, H 2, that gives it a low melting point? What evidence is there that H 2 has a low melting point?

7 6. Identify the likely type of substance for each of the following: CCl 4, LiNO 3, Ga, H 2 O, F 2, CH 3 Cl, CH 3 NH 2, KCl. Include in your answer both propery-based information AND mathematically-based information. Explain each answer. 7. Why do ionic substances tend to dissolve well in water? Describe the process of solvation.

8 8. Substance X is tested and found to have a boiling point of 278 o C. It is soluble in water, but not in oil. When dissolved in water, it will conduct electricity, but it will not conduct electricity in its solid form. What type of substance is it most likely to be AND what other properties is it likely to have? Explain your answer fully. 9. Substance Y has a melting point of o C, it will not dissolve in water, but will dissolve in oil. Based on just these properties, what type of substance is it likely to be AND what other properties is it likely to have? Explain fully Substance Z will not dissolve in either water or oil. It does not conduct heat or electricity well and it shatters when subjected to extreme twisting. What kind of melting point is it likely to have? What kind of substance is it most likely? What are some other likely properties of Substance Z? Explain your answers fully.

9 WHAT TO USE: SiO 2 (sand) graphite (pencil lead) I 2 NaCl sugar H 2 O ammonia CuSO 4 /other salts Br 2 penny (remember not pure copper) available metals