Join Jessi, Mister Brown, and Squeaks as they explore and discover all kinds of science in everyday foods, like popcorn, pickles, and more, here on SciShow Kids! Second Grade Next Generation Science Standards Crosscutting Concept: Cause and Effect: Events have causes, sometimes simple, sometimes multifaceted. Deciphering causal relationships, and the mechanisms by which they are mediated, is a major activity of science and engineering. Disciplinary Core Ideas: PS1.A: Structure and Properties of Matter - Different kinds of matter exist and many of them can be either solid or liquid, depending on temperature. Matter can be described and classified by its observable properties. (2-PS1-1). PS1.B: Chemical Reactions - Heating or cooling a substance may cause changes that can be observed. Sometimes these changes are reversible, and sometimes they are not (2-PS1-4). Performance Expectations: 2-PS1-1. Plan and conduct an investigation to describe and classify different kinds of materials by their observable properties. 2-PS1-4. Construct an argument with evidence that some changes caused by heating or cooling can be reversed and some cannot.