Alaska Science Performance Standard L3/A8a

Alaska Science
Key Element A8a

A student who meets the content standard should understand the scientific principles and models that describe the nature of physical, chemical, and nuclear reactions (Energy Transformations).

Performance Standard Level 3, Ages 11–14

Students investigate common physical and chemical changes and the characteristics associated with each type of change, and relate these changes to simple rearrangements of atoms.

Sample Assessment Ideas

Students conduct tests with cabbage juice indicator, and common household substances to determine if they are an acid or a base.
Students compare cookies or cake recipe ingredients (or mix) with the cooked product; compare taste, smell, texture and appearance; explain what happened in terms of irreversible chemical changes.

Expanded Sample Assessment Idea

Expanded Sample Assessment Idea

Students investigate the reaction of iron and sulfur to form iron sulfide and build structural models to help explain the reaction and the conservation rules involved

Materials test tubes iron filings magnet balance (if available) heater (Bunsen burner or flame) sulfur powder magnifying glass Procedure NOTE: Proper safety procedures must be followed! Students will: Make careful observation of the properties of iron filings and sulfur (including: hardness, color, crystal shape, magnetic properties, solubility/reaction in water); make quantitative measurements of the mass of the iron filings and sulfur; describe and record in journal. Add one scoop of each starting material into a test tube, and heat strongly (SAFETY NOTE—take care not to catch sulfur on fire); cool. Make careful observation of the properties of the product removed from the test tube (including: hardness, color, crystal shape, magnetic properties, solubility/reaction in water); make quantitative measurements of the mass of the product; describe and record in journal. Build models of iron, sulfur and iron sulfide; use the models to discuss physical and chemical properties, and physical and chemical changes. Reflection and Revision What properties do the substances have in common? What properties are different? What is the evidence of physical change? What is the evidence of chemical change? Explain why some students find that the product is magnetic and some do not.	Levels of Performance
	Stage 4	Student work is complete, correct and shows evidence of logical reasoning and the transfer and extension of knowledge regarding chemical vs. physical change and properties. Student work includes detailed observations and accurate models that demonstrate the conservation of atoms in chemical reactions. The models are used to interpret experimental observations including the presence of non-reacted materials and the principle that correct ratios are required for a complete reaction.
	Stage 3	Student work is mostly complete and shows evidence of reasoning and the transfer or extension of knowledge regarding chemical vs. physical change and properties. Student work may contain minor errors or omissions but it includes some detailed observations as well as models that demonstrate the interaction of atoms in chemical reactions. The models are used to explain some experimental observations and the need for correct ratios.
	Stage 2	Student work may be incomplete, and shows limited evidence of knowledge regarding the difference between physical and chemical properties or changes. Experimental observations lack detail, models may show evidence of skilled craftsmanship but flawed reasoning is used to explain chemical reactions.
	Stage 1	Student work is mostly incomplete and shows evidence of misconceptions regarding physical and chemical properties and changes. Observations are minimal or totally incorrect and models may be incorrect or cannot be used to explain chemical reactions.

Standards Cross-References
( Alaska Department of Education & Early Development Standards)

National Science Education Standards

Substances react chemically in characteristic ways with other substances to form new substances (compounds) with different characteristic properties. In chemical reactions, the total mass is conserved. Substances often are placed in categories or groups if they react in similar ways; metals is an example of such a group. (Page 154)

Chemical elements do not break down during normal laboratory reactions involving such treatments as heating, exposure to electric current, or reaction with acids. There are more than 100 known elements that combine in a multitude of ways to produce compounds, which account for the living and nonliving substances that we encounter. (Page 154)

In most chemical and nuclear reactions, energy is transferred into or out of a system. Heat, light, mechanical motion, or electricity might all be involved in such transfers. (Page 155)

Benchmarks

Atoms and molecules are perpetually in motion. Increased temperature means greater average energy of motion, so most substances expand when heated. In solids, the atoms are closely locked in position and can only vibrate. In liquids, the atoms or molecules have higher energy of motion, are more loosely connected, and can slide past one another; some molecules may get enough energy to escape into a gas. In gases, the atoms or molecules have still more energy of motion and are free of one another except during occasional collisions. (Page 78)

There are groups of elements that have similar properties, including highly reactive metals, less reactive metals, highly reactive nonmetals (such as chlorine, fluorine, and oxygen), and some almost completely nonreactive gases (such as helium and neon). An especially important kind of reaction between substances involves combinations of oxygen with something else—as in burning or rusting. Some elements don’t fit into any of the categories; among them are carbon and hydrogen, essential elements of living matter. (Page 78)

No matter how substances within a closed system interact with one another, or how they combine or break apart, the total weight of the system remains the same. The idea of atoms explains the conservation of matter: if the number of atoms stays the same no matter how they are rearranged, then their total mass stays the same. (Page 79)

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