Let's break down each part step-by-step: --- # **A. Bunsen Burner** ### 1. Instructor’s Approval - **This is for your instructor to sign after you've shown them a well-adjusted Bunsen flame.** --- ### 2. a. **Sketch of Heat Zones** - **Describe and Sketch:** For a nonluminous (blue) flame: - There are two primary zones: 1. **Inner (Cool) Zone:** Near the base, inside the flame, appears blue or almost invisible. This area is cooler because the gas is still mixing with air and hasn't fully combusted. 2. **Outer (Hot) Zone:** The tip and outside edge of the flame. This is where complete combustion occurs, and it's the hottest part of the flame. - **Label the “cool” and “hot” zones** on your sketch as described above. #### **[Text description for sketch if drawing is not possible]:** ``` ^ | (outer, hottest part, blue) | [HOT ZONE] | --------------- [COOL ZONE] (inner, lower part, pale blue) --------------- | (Burner barrel) ``` - **Wire gauze** should be placed horizontally above the barrel, parallel to it. --- ### 2. b. **Effect of Closing Air-Control Valve** - **When the air-control valve is closed (nearly closed):** - Less air mixes with gas. - The flame turns yellow and becomes luminous ("luminous flame"). - The inner (cool) zone grows larger, and the outer (hot) zone shrinks and becomes less hot. - The flame is less efficient, produces soot (carbon), and is not as hot. --- # **B. Laboratory Balances** ### 1. **Measuring Mass** - **Fill in the table with the mass of each object using your balance.** - Record the **description** (size/volume) and **mass (g)** for each item: - Test tube - Beaker - Spatula - Graduated cylinder - Other (as specified) --- ### 2. **Precision of Measurement** **Balance no.:** (Fill in your assigned balance number) #### a. **Mass of Cylinder + 7 mL H₂O** - For each trial, record the mass of the graduated cylinder **plus** water. #### b. **Mass of 7 mL H₂O (g)** - Subtract the mass of the empty graduated cylinder from the value in part a for each trial: \[ \text{Mass of 7 mL H}_2\text{O} = \text{(Mass of cylinder + water)} - \text{(Mass of cylinder)} \] #### c. **Average Mass of 7 mL H₂O** - Calculate the average: \[ \text{Average mass} = \frac{\text{Sum of all 7 mL H}_2\text{O masses}}{\text{Number of trials}} \] #### d. **Comment on Precision** - **Precision:** If the values from all trials are close to each other, your measurements are precise. - **Example comment:** "The mass measurements for the water samples were consistent across all trials, indicating high precision." --- ## **Summary/Final Answers** ### **A. Bunsen Burner** - **a.** Sketch and label as described. - **b.** When the air-control valve is closed, the cool zone increases, the hot zone decreases, and the flame becomes yellow and less hot. ### **B. Laboratory Balances** - **1.** Fill in the table with measured masses. - **2.** Calculate masses for each trial, the average, and comment on the precision as shown. --- **If you provide your specific data for the balances, I can help you calculate the actual answers!**