Day 1: Evidence of Chemical Reactions Lab

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Objective

TSWBAT identify the difference between a chemical reaction and a physical change.

Big Idea

Using Pasco probeware students perform a series of experiments to gather evidence of chemical reactions.

NGSS Alignment

Performance Expectation (PE)/Disciplinary Core Idea (DCI)

This lesson is aligned with HS-PS1-7, the uses of mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction; and DCI-PS1.B, the fact that atoms are conserved, together with knowledge of the chemical properties of the elements involved, can be used to describe and predict chemical reactions. One important part of predicting chemical reactions is to recognize that a chemical reaction has occurred and not just a physical change.  One evidence that a chemical reaction has occurred is the first step in understanding chemical properties.  This investigation has students predict whether a change in properties is chemical or physical. 

Science and Engineering Practices (SEP)

Practice 3 Planning and Carrying Out Investigations- Students plan an investigation test a design collaboratively to produce data to serve as the basis for evidence as part of building and revising models, supporting explanations for phenomena, or testing solutions to problems. Consider possible confounding variables or effects and evaluate the investigation’s design to ensure variables are controlled.

Practice 4 Analyzing and Interpreting Data-Students analyze data using tools, technologies, and/or computational models in order to make valid and reliable scientific claims or determine an optimal design solution

Crosscutting Concepts (XC)

During this lesson students will recognize Matter and Energy are a part of chemical reactions.  While preforming this investigation students are expected to see that matter is conserved because atoms are conserved in chemical and physical chemical processes.  Warm-up 5 minutes

The previous day students finished the lesson by categorizing 10 different reaction into the five different reactions types: synthesis, decomposition, single replacement, double replacement and combustion.  To start the class, I have student write down on a single sheet of paper one example of each.  They are told to use their notes to aid them in this.  This will help them recall what was learned from the previous day.  After a five minutes I have them turn it, so that I can look at it after class.

Getting Started with PASCO

5 minutes

This a two day lab so it is important to provide students with proper instruction, otherwise it can turn into a 3 day lab and safety can become an issue too.  

This is the second time students have used PASCO Probeware, so they still need to be walked through the process of downloading the lab.  In order to use the download your will need their software installed and Advanced Chemistry Sensor.

This lab is a great lab that introduces several chemistry and general science concepts: chemical change, physical change, endothermic reactions, exothermic reactions, unknown identification and basic procedural application.  This lab is not a difficult lab, but does require following detailed procedures, step by step. 

Some of the reactions require students to calculate a temperature change, if PASCO equipment is not available a thermometer or digital temperature probe will work too.  However, without the sensitivity and accuracy of the PASCO equipment the graphing will be difficult and students might only be able to state that the reaction is endothermic or exothermic. 

Lab Challenge

10 minutes

I give students approximately 10 minutes to complete this portion of the lab.  I don't like to spend too much time because I like to walk them through some of the materials they will use and correct operation of probeware.  

Safety and Material

5 minutes

Set up for this lab can take up to 2 hours if you don't have the chemicals made up in advance.  I recommend sharing the duties with as many teachers as possible and making enough so that in years to come you only have to fill the dropper bottles.  I also put all the materials on a cart so that the other teachers can use when my students are finished with the lab.

Reaction 1 Student Walk Through

20 minutes

One of the most critical aspects of the first reaction is having them read and execute every instruction as it states and not before it's stated.  I found that a lot of kids want to rush through the steps and end up not recording accurate data.  It take a little time, but if the process is demonstrated on the over head students will have no difficulty for the rest of the experiment following the steps as they are stated.

 

Clean-up and Student Work

10 minutes

I leave a little more time on day one too ensure that all equipment is returned properly to its original condition.  This way all classes know exactly what everything looks like and how it should look everyday.  This lab uses a large amount of materials and can easily become dangers if students don't keep things organized for day 2.  Some safety concerns that should be observed:  broken glass from test tubes, chemicals spills, wires from probeware and hot plates.  Below is a video of two student's work, one that is  Exemplary and one that is require a little more effort.