pre lab assignment 17d question 3

• Basics for GSIs
• Advancing Your Skills

Pre-Lab Assignments

For students in lab courses, nothing feels more pointless than just going through the motions of a lab procedure without understanding why it is significant. Emphasize to students that experimental science is the basis for the models they learn about in lecture. Lab, unlike lecture, represents professional science in practice. Lab also represents a playground where curiosity is sparked and scientific theories are put to the test. If students recognize this, they will gain a better understanding of what science truly is and may be more motivated in their lab work.

Preparing students for lab involves the following:

• Helping students understand the models, theories, and principles addressed in the lab procedure — giving them a conceptual framework for the lab
• Ensuring that students know how the lab fits into the course content
• Outlining the lab procedure and data analysis
• Orienting students to the relevant equipment and safety procedures

A well designed pre-lab assignment can serve all these functions. Pre-lab assignments are tasks or homework that students complete before arriving in class for the lab period. Pre-lab assignments motivate students to prepare for the lab and help them connect conceptual understanding with an experiment.

There are several advantages for students in using a pre-lab assignment:

• Students come better prepared for the lab exercise.
• Experiments and exercises go more smoothly because students are familiar with the processes.
• Their understanding of the material is heightened.

There are advantages for the instructor as well:

• The assignment can streamline the process of writing a  pre-lab introduction .
• The assignment can make it easier to teach the theory behind the lab, since students will have a firmer understanding of the principles behind it.

For many of the lab classes you will teach, the professor may already have pre-lab assignments written for you to give your students. However, in cases where there are no pre-lab assignments written into the course already, you may choose to create and implement your own.

Designing a Pre-Lab Assignment

Concepts and types of questions.

First, think about the models and questions you feel are important to address in a pre-lab assignment. What do you want your students to have understood or thought about before they arrive in lab?

In order to help students frame the lab experiment, consider the main question your students should become able to answer:

• What question is this lab experiment answering?
• How will your data answer this question?
• How will you collect this data?
• How will you minimize ambiguity and control variables?

Here are some of the topics you might ask your students to think about in a pre-lab exercise:

• concepts, theory, and models
• procedure and methods (for an example see the Teaching Effectiveness Award essay by Jessica Smith [Chemistry],  A Pre-Lab Assignment for a More Efficient and Effective Laboratory )
• troubleshooting and other experimental issues
• prediction of trends in data or other qualitative questions about data
• quantitative questions such as calculations with simulated data
• interpretation of simulated results

Linking to the Pre-Lab Introduction

It is important to consider how you will introduce the lab on the day of the lab section. It is most common to give a short  pre-lab introduction .

• Connecting the questions and concepts addressed in your pre-lab assignment with those that you plan to address in your pre-lab introduction helps make certain that these two aspects of lab preparation complement each other.
• Use discussion of the pre-lab assignment as a starting point for the pre-lab introduction and as a tool for introducing the lab. In fact, you should go over at least some part of the pre-lab assignment at the beginning of the lab period. This ensures that students have understood the material and concepts therein before the lab exercise begins.

Here are several ways that you may format your pre-lab assignment, each with advantages or disadvantages depending on the material, your class, and the outcomes you wish to achieve from the assignment:

• Worksheet done before lab  (handed in at the beginning of lab): This format works well if you can create well-defined questions to help your students consider some theory or concepts related to the lab. Sometimes giving students sample calculations, data, or experiments on a worksheet is also helpful, if the lab material lends itself to this approach.
• Assignment worth a few points  (handed in at the beginning of lab): This is useful when preparing for the lab requires students to research information on their own. You can also make this a small group assignment that a lab group or lab partners can do together to prepare for lab or to think about important concepts relating to the lab.
• Quiz at the start of lab : This is most useful if you want to ensure your students are preparing for lab on their own by reading the lab or background materials in advance. Again, it works well if the quiz can function as a starting point for discussion or an introduction to the lab.
• Preparation of lab notebook  (checked at the start of lab): This can work well if having a comprehensive lab notebook is crucial to the students’ understanding of the lab material (anatomy courses, involving dissections and labeling structures, are one example). Checking the students’ lab notebooks can help confirm that students are making the best use of their lab time and taking away the most valuable information from the lab. It also is an incentive for students to organize their lab material well, thus maximizing the benefits of the lab period.
• Quiz on the web to be completed before class  (currently implemented in Chemistry 1A at UC Berkeley): Pre-lab web quizzes can be an excellent way to use technology to help your students prepare for lab. Having students take the quiz on the web before class will alert you to problems that students are having in understanding lab material. You can then take this into consideration when introducing the lab on the day of section.

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

8.1: Pre-lab Assignment

• Last updated
• Save as PDF
• Page ID 425146

• Kathryn Haas
• Duke University

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Please complete the general pre-lab assignment.

• school Campus Bookshelves
• menu_book Bookshelves
• perm_media Learning Objects
• login Login
• how_to_reg Request Instructor Account
• hub Instructor Commons

Margin Size

• Download Page (PDF)
• Download Full Book (PDF)
• Periodic Table
• Physics Constants
• Scientific Calculator
• Reference & Cite
• Tools expand_more
• Readability

selected template will load here

This action is not available.

3.3: Pre-lab Questions

• Last updated
• Save as PDF
• Page ID 40164

• Kelly C. Burke
• College of the Canyons

\( \newcommand{\vecs}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vecd}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash {#1}}} \)

\( \newcommand{\id}{\mathrm{id}}\) \( \newcommand{\Span}{\mathrm{span}}\)

( \newcommand{\kernel}{\mathrm{null}\,}\) \( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\) \( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\) \( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\inner}[2]{\langle #1, #2 \rangle}\)

\( \newcommand{\Span}{\mathrm{span}}\)

\( \newcommand{\id}{\mathrm{id}}\)

\( \newcommand{\kernel}{\mathrm{null}\,}\)

\( \newcommand{\range}{\mathrm{range}\,}\)

\( \newcommand{\RealPart}{\mathrm{Re}}\)

\( \newcommand{\ImaginaryPart}{\mathrm{Im}}\)

\( \newcommand{\Argument}{\mathrm{Arg}}\)

\( \newcommand{\norm}[1]{\| #1 \|}\)

\( \newcommand{\Span}{\mathrm{span}}\) \( \newcommand{\AA}{\unicode[.8,0]{x212B}}\)

\( \newcommand{\vectorA}[1]{\vec{#1}}      % arrow\)

\( \newcommand{\vectorAt}[1]{\vec{\text{#1}}}      % arrow\)

\( \newcommand{\vectorB}[1]{\overset { \scriptstyle \rightharpoonup} {\mathbf{#1}} } \)

\( \newcommand{\vectorC}[1]{\textbf{#1}} \)

\( \newcommand{\vectorD}[1]{\overrightarrow{#1}} \)

\( \newcommand{\vectorDt}[1]{\overrightarrow{\text{#1}}} \)

\( \newcommand{\vectE}[1]{\overset{-\!-\!\rightharpoonup}{\vphantom{a}\smash{\mathbf {#1}}}} \)

Read the Microscopy chapter in your textbook prior to lab.

• Compare and contrast Bright-field, Dark-field, and Phase Contrast microscopy.
• What would the total magnification be for the following?
• Why is it often necessary to stain specimens?
• Give an advantage of dark-field or phase contrast microscopy over bright-field.

Parts of the Compound Microscope

Label the parts of the microscope indicated by the arrows:

Contributors and Attributions

Kelly C. Burke ( College of the Canyons )

Module 3: Percent Composition Laboratory

Lab 3 worksheet, experimental procedure and data.

• Have your instructor check your set up before you proceed with the lab. It is important to have your set-up ready before you move on.
• Using a graduated cylinder, transfer 5.0 mL of the standard 4M HCl into the flask.
• You will be supplied with a sample of either of three metals, Ca, Al or Mg. Tare a weigh boat on an analytical balance. Accurately weight ~0.04-0.05 g of the metal in the weigh boat.
• Record the exact mass to be used in your data section (you should have three decimal points).
• Pour the entire metal sample from the weigh boat directly into the flask containing the HCl solution and immediately stopper the flask . Be careful that all of the metal gets into the acid and does not stick to the side of the flask. If it does, gently swirl the flask to release the metal into the acid.
• The hydrogen gas produced by the reaction will displace water from the measuring cylinder. Calcium and magnesium will react vigorously; aluminium will react rapidly after a short induction period of several minutes.
• If you do NOT see the bubbles being released into the graduated cylinder, you may need to firmly hold the stopper onto the flask to make sure there is not a leak.
• When reaction is complete (no further evolution of gas) cool the flask by holding it in the water bath for a few minutes if it has become too hot. When the flask is a room temperature, raise or lower the measuring cylinder to equalise the water levels inside and out, as illustrated below, and record the volume of gas evolved.
• Once the water level is equal to the level of gas in the cylinder, record the volume of gas produced in your data section.
• Run two trials. Record all data.

Pre-lab Assignment/Questions

*Note – this pre-lab must be finished before you come to lab.

1. Use Equation 1 to write the formula for magnesium chloride and balance the following equation for the reaction of magnesium with hydrochloric acid.

Mg+_________HCl →MgCl_____+ _______H 2(g)

2. If the metal used was Al, use Equation 1 to determine the mol ration of metal to hydrogen gas.

______ mol Al = _____moles of H 2

3. Determine the percent composition of the metal in the AlCl3.

4. A student performs the lab on an unknown metal and obtains the following data:

Using this data, complete the following calculations:

• moles of H 2 gas = (V * P) / (R * T): ________________
• Molar ratio of H:M assuming a 1:1 ratio of M to H2. We will assume a 1:1 molar ratio for this experiment.
• Moles of metal used: ________________
• Atomic mass of metal = g metal used / moles of metal. ________________

Possible identity of the metal: ____________________

Experimental Data and Results

Metal Used __________________________________________

Calculations

Average atomic mass of metal ___________________

Atomic mass of metal of from the periodic table _____________

% Error of your measured atomic mass of the metal ____________________

Results, Discussions and Post-Lab Questions

1. Determine the percent composition of the metal in the metal chloride produced in your experiment.

2. The measurement of the mass of metal should be precise to 0.001 g in 0.5 g; that is, to 0.2%. Thus the largest source of error in obtaining the atomic mass of the metal is likely to be the measurement of the volume of gas evolved.

a. Calculate the atomic mass of the metal if the volume measured in the prelab problem #4 was 30.0 mL instead of 26.5 mL still assuming a 1 to 1 ratio between the moles of metal used and the moles of H 2 gas produced.

b. What then would be the best estimate of the metal used?

3. Copper is a transition metal that can have more than one charge. Write the equation of Cu +  reacting with hydrochloric acid. Then write the reaction of Cu 2+ reacting with hydrochloric acid. How does the amount of hydrogen gas evolved change with each?

4. Give two possible sources of error in your experiment. Explain how would each affect the true value (would the atomic mass of the metal be calculated too high, too low or be unaffected)?

• ID of An Unknown Chloride Salt. Authored by : Lucinda Spryn . Provided by : Thomas Nelson Community College . Located at : https://lumen.instructure.com/courses/150410/files/21351919?module_item_id=5308063 . License : CC BY: Attribution
• College Chemistry 1. Authored by : Jessica Garber-Morales. Provided by : Tidewater Community College. Located at : http://www.tcc.edu/ . License : CC BY: Attribution