Using Chemical Change to Identify an Unknown

Learning Resource Type

Classroom Resource

Subject Area

Science

Grade(s)

8

Overview

In this lesson, students will use test liquids on different known powders and observe their reactions. Then students will use these characteristic chemical changes to help them identify an unknown powder.

Students will be able to identify and control variables to develop a test to identify an unknown powder. Students will be able to explain that a substance reacts chemically in characteristic ways and that these characteristics can be used to identify an unknown substance.

Science (2015) Grade(s): 8

SC15.8.2

Plan and carry out investigations to generate evidence supporting the claim that one pure substance can be distinguished from another based on characteristic properties.

UP:SC15.8.2

Vocabulary

  • Investigation
  • Claims
  • Evidence
  • Substance
  • Matter
  • Composition
  • Property
  • Element
  • Compound
  • Pure substance
  • Characteristic properties
  • Physical property (includes, but not limited to, color, odor, density, melting point, boiling point, solubility)
  • Chemical property (includes, but not limited to, flammability, reactivity with water, pH)

Knowledge

Students know:
  • A substance is matter which has a specific composition and specific properties.
  • Every pure element is a substance. Every pure compound is a substance.
  • Pure substances have characteristic properties.
  • Characteristic properties are physical or chemical properties that are not affected by the amount or shape of a substance.
  • Characteristic properties can be used to identify a pure substance.
  • Physical properties of a substance are characteristics that can be observed without altering the identity (chemical nature) of the substance.
  • Color, odor, density, melting temperature, boiling temperature, and solubility are examples of physical properties.
  • Chemical properties of a substance are characteristics that can be observed but alter the identity (chemical nature) of the substance.
  • Flammability, reactivity with water, and pH are examples of chemical properties.

Skills

Students are able to:
  • Identify the phenomena under investigation, which includes pure substances and their characteristic properties.
  • Identify the purpose of the investigation, which includes demonstrating that one pure substance can be distinguished from another based on characteristic properties.
  • Develop a plan for the investigation individually or collaboratively.
  • Describe factors used in the investigation including appropriate units (if necessary), independent and dependent variables, controls and number of trials for each experimental condition.
  • Perform the investigation as prescribed by the plan.
  • Make a claim, to be supported by evidence, to support or refute an explanation or model for a given phenomenon, including the idea that one pure substance can be distinguished from another based on characteristic properties.
  • Identify evidence to support the claim from the given materials.
  • Evaluate the evidence for its necessity and sufficiency for supporting the claim.
  • Use reasoning to connect the evidence and evaluation to the claim that one pure substance can be distinguished from another based on characteristic properties.

Understanding

Students understand that:
  • Each pure substance has characteristic physical and chemical properties (for any bulk quantity under given conditions) that can be used to identify it.
  • Pure substances can be distinguished from other pure substances based on characteristic properties.
  • Substances react chemically in characteristic ways. In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.

Scientific and Engineering Practices

Planning and Carrying out Investigations

Crosscutting Concepts

Patterns
Science (2015) Grade(s): 8

SC15.8.5

Observe and analyze characteristic properties of substances (e.g., odor, density, solubility, flammability, melting point, boiling point) before and after the substances combine to determine if a chemical reaction has occurred.

UP:SC15.8.5

Vocabulary

  • Characteristic properties (e.g., odor, density, solubility, flammability, melting point, boiling point)
  • Substances
  • Chemical reaction

Knowledge

Students know:
  • Each pure substance has characteristic physical and chemical properties that can be used to identify it.
  • Characteristic properties of substances may include odor, density, solubility, flammability, melting point, and boiling point.
  • Chemical reactions change characteristic properties of substances.
  • Substances react chemically in characteristic ways.
  • In a chemical process, the atoms that make up the original substances are regrouped into different molecules, and these new substances have different properties from those of the reactants.

Skills

Students are able to:
  • Observe characteristic physical and chemical properties of pure substances before and after they interact.
  • Analyze characteristic physical and chemical properties of pure substances before and after they interact.
  • Analyze the properties to identify patterns (i.e., similarities and differences), including the changes in physical and chemical properties of each substance before and after the interaction.
  • Use the analysis to determine whether a chemical reaction has occurred.

Understanding

Students understand that:
  • Observations and analyses can be used to determine whether a chemical reaction has occurred.
  • The change in properties of substances is related to the rearrangement of atoms in the reactants and products in a chemical reaction (e.g., when a reaction has occurred, atoms from the substances present before the interaction must have been rearranged into new configurations, resulting in the properties of new substances).

Scientific and Engineering Practices

Analyzing and Interpreting Data

Crosscutting Concepts

Patterns

CR Resource Type

Lesson/Unit Plan

Resource Provider

Other

License Type

CUSTOM

Resource Provider other

American Chemical Society
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