Day 3: Expressions and Operators

Learning Objectives

• AAP-1.D: For data abstraction: Develop data abstraction using lists to store multiple elements.
• AAP-2.B: Represent a step-by-step algorithmic process using sequential code statements.
• AAP-2.C: Evaluate expressions that use arithmetic operators.

Essential Questions

• How are expressions evaluated in a program?
• How do operators allow us to manipulate data in meaningful ways?

Materials Needed

• Presentation slides on expressions and operators
• Programming environment
• Expression evaluation worksheet
• Debugging exercise handouts
• Exit ticket templates

Vocabulary

• Expression
• Operator
• Arithmetic operator
• Operand
• Evaluation
• Order of operations
• Precedence
• Syntax error

Procedure (50 minutes)

Opening (8 minutes)

1. Review and Connection (3 minutes)

   • Review variables and assignments from previous lesson
   • Connect to today's focus on expressions and operators

2. Warm-up Activity (5 minutes)

   • Display several arithmetic expressions and ask students to evaluate them
   • Discuss how order of operations applies in programming

Main Activities (32 minutes)

3. Lecture: Arithmetic, Relational, and Logical Operators (12 minutes)

   • Define expressions as combinations of values, variables, operators, and procedure calls
   • Explain that expressions are evaluated to produce a single value
   • Introduce arithmetic operators:
     • Addition (+)
     • Subtraction (-)
     • Multiplication (*)
     • Division (/)
     • Modulus (MOD)
   • Demonstrate how each operator works with examples
   • Explain order of operations and precedence rules
   • Briefly introduce relational operators (=, ≠, >, <, ≥, ≤) and logical operators (AND, OR, NOT)
   • Show how operators can be combined in complex expressions

4. Demo: Order of Operations in Expressions (8 minutes)

   • Walk through the step-by-step evaluation of complex expressions
   • Show how parentheses can be used to control evaluation order
   • Demonstrate common mistakes in expression writing
   • Show how the same expression can be written in different ways
   • Compare mathematical notation with programming notation

5. Hands-on: Writing and Evaluating Expressions (12 minutes)

   • Students work in the programming environment
   • Guide students through writing expressions with different operators
   • Have students predict the result of expressions before running them
   • Include exercises with variables in expressions
   • Challenge students to write expressions for specific scenarios (e.g., converting temperatures, calculating averages)

Closing (10 minutes)

6. Activity: Debugging Expressions with Syntax Errors (5 minutes)

   • Provide students with expressions containing common errors
   • Students identify and fix the errors
   • Discuss common mistakes and how to avoid them
   • Emphasize the importance of careful syntax in expressions

7. Exit Ticket and Preview (5 minutes)

   • Students write and evaluate expressions with multiple operators
   • Preview that next class will focus on strings and string operations

Assessment

• Formative: Participation in hands-on activities and debugging exercises
• Exit Ticket: Accuracy of expression writing and evaluation

Differentiation

For Advanced Students

• Provide more complex expressions to evaluate
• Introduce additional operators or functions
• Challenge them to create expressions that solve real-world problems

For Struggling Students

• Provide step-by-step evaluation guides
• Focus on simpler expressions with fewer operators
• Use visual aids to illustrate order of operations

Homework/Extension

• Complete a worksheet with expression evaluation exercises
• Create a calculator program that uses expressions to perform calculations
• Research how different programming languages handle division and modulus

Teacher Notes

• Emphasize that expressions always evaluate to a single value
• Watch for confusion about division (/ in programming often performs floating-point division)
• Make connections to mathematical concepts students already know
• Consider using physical manipulatives to demonstrate expression evaluation
• Remind students that understanding expressions is essential for writing effective programs