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Effects of Concentration on Silver Crystal Growth

Title
Effects of Concentration on Silver Crystal Growth

Author(s) Patricia Gonzalez

Question

What is the effect of concentration of AgNO3 on silver crystal growth?

Standards

1. The periodic table displays the elements in increasing atomic number and shows how periodicity of the physical and chemical properties of the elements relates to atomic structure. As a basis for understanding this concept:
a. Students know how to relate the position of an element in the periodic table to its atomic number and atomic mass.
 
3. The conservation of atoms in chemical reactions leads to the principle of conservation of matter and the ability to calculate the mass of products and reactants. As a basis for understanding this concept:
a. Students know how to describe chemical reactions by writing balanced equations.
d. Students know how to determine the molar mass of a molecule from its chemical formula and a table of atomic masses and how to convert the mass of a molecular substance to moles, number of particles, or volume of gas at standard temperature and pressure.

6. Solutions are homogeneous mixtures of two or more substances. As a basis for understanding this concept:
d. Students know how to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent composition.

Investigation and Experimentation
1. Scientific progress is made by asking meaningful questions and conducting careful investigations. As a basis for understanding this concept and addressing the content in the other four strands, students should develop their own questions and perform investigations. Students will:

a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.

Experimental Design

The purpose of this study was for students to come up with variables that would affect silver crystal growth rate.  Students came up with various ideas of what variables they could alter and monitor.  Some ideas included changing the surface area of Cu source, changing the temperature in which the crystals were growing, changing the shape of the copper (we used pennies having a curved shape and flat tops and spheres).  Another group wanted to test whether the shape of the copper source would affect the shape of the silver crystal.  We decided in the end to change the concentration of AgNO3 solution to see if it changed the rate of crystal growth.  Most students hypothesized that if we increased the concentration of silver nitrate solution 10x that we would see an increase in the rate of crystal growth.  The students hypothesized this was because there would be 10x more Ag ions avaiable for exchange with the copper Cu ions. 

Independent variable
    • Silver Nitrate Concentration
      • Copper surface area, temperature, copper source shape (not shown here)
Dependent variables
    • Silver crystal growth rate
    • Silver crystal shape (not shown here)
Series
    • copper penny with 0.1M AgNO3
    • copper penny with 1M AgNO3
Constants
    • copper penny with water
 

Materials

graph paper for Petri dish
Petri dish
0.1M AgNO3 solution
1M AgNO3 solution
water
eye dropper
copper
ProScope HR 50x magnifying camera, base
computer
 
  • Procedures

  • Sample data and graphs

  • Photographs of experimental setup
  • References - provide links to websites; use APA style for bibliography
  •  
     

    Photographs and Movies

    Penny 0.1 M AgNO3

     

    Penny 1M AgNO3

     Sample data and graphs



    References



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