Rock Cycle - Chemistry (5)
Pre Lab 

  • Distinguishing between a chemical and physical change.
  • Describing a chemical reaction.
  • compound
  • element

Students use the periodic table to investigate elements and how they react in nature.

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The periodic table lists the elements in order of increasing atomic number. Each element is described by its name, atomic weight, atomic symbol, and atomic number. Elements with similar characteristics are listed in vertical groups called families.

Elements are composed of small particles called atoms. Atoms are the smallest units of an element that can combine with other elements. Atoms of different elements combine to form compounds. Baking soda (sodium bicarbonate), for example, is made of sodium, hydrogen, carbon, and oxygen. Hydrogen gas, composed of two hydrogen atoms is technically a compound. The chemical formula of a compound lists all the elements that make up the compound and their proportions. The smallest unit of a compound is a molecule.

A physical property of an element or compound is any characteristic that can be observed such as color, odor, density, hardness, or melting point. A chemical property refers to the chemical composition of that substance. For example, silicon (Si) and oxygen (O) make up quartz, silicon dioxide (SiO2). A physical change occurs when a compound changes state, for example, ice melting to form water. No new elements or compounds are formed. Physical changes require no modification of the internal molecular arrangement of the compound.

A chemical change occurs when a new compound is produced as a result of a reaction between two substances. Chemical changes cause permanent changes in the composition of the material, for example wood changes composition when burned to ash.

  1. Review the Periodic Table with the students. Ask them to find elements that are used in daily language. For instance: ______ Valley (Silicon); _____ makes strong bones (calcium); _____ helps fight a sore throat (zinc); a coin is named after this element (nickel). See if the students can come up with more examples. This will help you determine the level of your student’s knowledge of the elements.
  2. Ask your students to determine whether each of the following is a chemical or physical change. You may want to demonstrate some of these changes before the students respond.
    1. bending a toothpick (physical)
    2. burning a match (chemical)
    3. burning sugar (chemical)
    4. making a cake from scratch (chemical)
    5. smashing a can (physical)
    6. making instant coffee (physical)
    7. melting ice to water (physical)
  3. Scientists use the atomic symbols of the elements to help record chemical reactions, because it is easy to write the reaction in this chemical "short hand." Go through the chemical reactions below with your students. You may want to have them use the Periodic Table to locate the symbols. Don't worry about the numbers in the equations.
    H2 + Cl2 ---------> 2 HCl
    hydrogen (a gas) + chlorine (a gas) yields 2 molecules of hydrochloric acid
    CuO + H ---------> Cu + H2O
    copper oxide + hydrogen (a gas) yields copper + water

    H2 + S ---------> H2S
    hydrogen (a gas) + sulfur yields hydrogen sulfide

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