Next Generation Science Standards

Performance Expectation

Construct and revise an explanation for the outcome of a simple chemical reaction based on the outermost electron states of atoms, trends in the periodic table, and knowledge of the patterns of chemical properties.

• Clarification Statement: Examples of chemical reactions could include the reaction of sodium and chlorine, of carbon and oxygen, or of carbon and hydrogen.
• Assessment Boundary: Assessment is limited to chemical reactions involving main group elements and combustion reactions.

There's no doubt your students have been dreaming of the day they get to don a lab coat and goggles and start mixing stuff together. We're all for the lab coat and goggles, but this performance expectation will help them understand why "mixing stuff together" without understanding what you're mixing can be a recipe for disaster.

Students will use what they know about valence electrons, patterns in the periodic table, and chemical properties to construct, and revise, an explanation for what happened during a chemical reaction. If this is what happened, we wish you all the best of luck.

Don't overreact, but these activity ideas are really awesome:

• Create several dice with different main group elements on each side. Have students roll two of the dice and then make a prediction about the reaction that will occur between their two elements.
• Provide small groups of students with four to eight different examples of simple reactions. As a group, they will use what they know about each element to predict the outcome of the reaction. They will then perform each experiment to test if their prediction was correct. Discuss any discrepancies between the prediction and the outcome.
• Set up stations around the room with mystery substances. Students will follow the instructions for each set of substances to see how they react (or don't react). They will then discuss what properties would be necessary for each reaction to occur and make a guess as to which substances they are working with. You may want to include a disclaimer about doing experiments with mystery substances and remind students that you know what the substances are and that they will react safely. Mixing unknown chemicals is always a bad idea.
• Assign each student to be a main group element. Then have them form two circles, one inside of the other so that they are facing one other student. Play some music (this is your opportunity to make them M.C. Hammer fans!) and have the circles rotate in opposite directions until the music stops. They will then discuss with the person in front of them what kind of reaction will occur between their two elements. Repeat for several more rounds, calling on random pairs to share their reactions to make it more interesting.

Disciplinary Core Ideas

PS1.A – Structures and Properties of Matter: The periodic table orders elements horizontally by the number of protons in the atom's nucleus and places those with similar chemical properties in columns. The repeating patterns of this table reflect patterns of outer electron states.

It turns out that the organization of the periodic table is pretty important and makes everyone's lives a lot easier. Students should know all about how elements are organized horizontally by the number of protons and vertically by the number of electrons in their outer shell. They should also know that there are patterns in how elements behave, which are based on their outer shell electrons. Their periodic table prowess should only help them as they put those patterns to work to describe how certain elements will react with one other.

PS1.B – Chemical Reactions: 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.

The best part about chemical reactions (other than feeling very scientist-y as white smoke billows out of your Erlenmeyer flask) is that the atoms don't go anywhere. They might recombine or change form, but they don't disappear in a poof of purple smoke. They're conserved. This makes understanding and describing chemical reactions so much easier.

Students should understand that they can use what they know about the chemical properties, in addition to the fact that the elements present at the start of the reaction are still there in some form at the end, to either make a prediction or describe what happened.

Conceptually, this shouldn't be too hard for students to grasp. In fact, knowing that atoms don't disappear or reappear randomly might actually make it easier for them to visualize a reaction. However, putting it into practice with balancing equations maybe prove a bit trickier. Using manipulatives and working in small groups should help students get the hang of it until they're ready to venture out on their own.

Science and Engineering Practices

Constructing Explanations and Designing Solutions: Construct and revise an explanation based on valid and reliable evidence obtained from a variety of sources (including students' own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.

Students will construct and revise an explanation for what happened during a simple chemical reaction. They will of course need to use valid evidence in their explanation and can even use evidence they've collected during their own experiments (time to bust out the goggles). Online simulations, or even videos of reactions, will do the trick too, if need be.

Your little mini-chemists will also need to understand that chemical reactions happen the same way today as they did in the past and will do in the future. Sodium and chlorine are destined to always react to form salt, so don't go trying to explain that one day they might instead form dragon saliva.

Crosscutting Concepts

Patterns: Different patterns may be observed at each of the scales at which a system is studied and can provide evidence for causality in explanations of phenomena.

The periodic table was built on patterns. This is a great thing for us, because can you even imagine trying to make sense of all of those elements if they were just mingling randomly with one another? It would be like trying to teach a porcupine to hula: frustrating and likely painful…

These patterns will make student's lives easier as they attempt to explain the results of simple chemical reactions. They can use what they know about chemical properties and valence electrons to support their reasoning for the outcome of a particular reaction. If sodium and chlorine are good bonding partners, then potassium will likely be a good fill-in for sodium, since the both of them are in the same column. That's the beauty of patterns. Will the students be confused about the periodic table? We don't zinc so.