Expansion - Linear, Area, and Volume

Grade 10 · Physics

Semester 2 | Period 4 | Week 22

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Subject: Physics

Semester: 2

Period: 4

Week: 22

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 10

Week & Period: Week 22, Period IV

Date:

Sub-topic: Expansion – Linear, Area, and Volume

Learning Objectives:
By the end of the lesson, learners should be able to:

  1. Define and distinguish between linear, area, and volume expansion.
  2. Explain the effects of heat on solids, liquids, and gases in terms of expansion.
  3. Identify real-life applications and consequences of expansion.
  4. Perform and solve calculations involving thermal expansion.

Instructional Materials:

  • Metal rods (iron, aluminum, copper)
  • Bunsen burner or spirit lamp
  • Tripod stand, retort stand with clamp
  • Expansion apparatus (Gravesand’s or Lee’s)
  • Rulers, vernier calipers, stopwatch
  • Beakers, water, mercury (for observation only)
  • Graph sheets and expansion coefficient tables

Anticipation (Warm-Up):
Ask: “Why do bridges have expansion joints? Why do power lines sag on hot afternoons?”

Building Knowledge:

  1. Thermal Expansion Overview:
    All materials expand when heated and contract when cooled. This is called thermal expansion.
  2. Types of Expansion:
    • Linear Expansion: Increase in length only.

ΔL=L0×α×ΔT

Area Expansion: Increase in surface area.

ΔA=A0×β×ΔT(β=2α

Volume Expansion: Increase in volume.

ΔV=V0×γ×ΔT(γ=3α)

  1. Thermal Expansivity (α):
    A material’s expansivity is a constant showing how much it expands per degree Celsius.

 

Solved Examples:

  1. A brass rod of 2.5 m expands by 0.003 m when heated from 30°C to 130°C. Find its linear expansivity:

α=ΔL

L0×ΔT=0.0032.5×100=1.2×10−5/∘C

α=L0×ΔTΔL=2.5×1000.003=1.2×10−5/∘C

  1. A cube of aluminum (volume = 500 cm³) is heated by 50°C. If γ=7.2×10−5/∘C, find the volume increase:

ΔV=500×7.2×10−5×50=1.8 cm3

ΔV=500×7.2×10−5×50=1.8 cm3

 

Experiment:
Title: Demonstrating Linear Expansion in Metal Rods

Apparatus:

  • Gravesand’s apparatus
  • Metal rod
  • Pointer & scale
  • Bunsen burner
  • Retort stand & clamp
  • Stopwatch

Procedure:

  1. Fix the rod horizontally using clamps.
  2. Attach pointer to free end.
  3. Record initial length.
  4. Apply heat uniformly.
  5. Observe and measure pointer movement.
  6. Calculate expansion using scale reading.

 

Activities:

  • Calculate linear expansion for different rods and temperatures.
  • Use graph sheets to plot expansion vs temperature.
  • Draw diagrams to illustrate expansion joints in bridges and railway tracks.
  • Identify why mercury expands in thermometers.

 

Assessment:

  1. Define linear, area, and volume expansion.
  2. A 3 m copper rod expands by 0.0027 m between 25°C and 95°C. Find α\alphaα.
  3. List two applications of expansion in daily life.
  4. What is the difference between expansivity of solids, liquids, and gases?

 

Homework:

  • Research and write a one-page summary on “Why expansion joints are used in highways and bridges.”
  • Find the volume expansion of a 400 cm³ liquid with γ=8×10−5/∘C heated by 30°C.

 

Expanded Notes:

  • Solids expand in length, area, and volume.
  • Liquids and gases expand mostly in volume.
  • Expansion can cause damage (e.g., broken glass in hot water) or be useful (e.g., thermostats).
  • Thermal expansion is reversible (materials return to original size when cooled).

 

Differentiation:

  • Diagrams and animations for visual learners.
  • Group calculations for peer learning.
  • Guided experiments for hands-on learners.
  • Extra practice sheets for slower learners.

Teacher’s Reflection:

  • Were learners able to relate expansion to real-life examples?
  • Did they correctly apply the formulas in calculations?
  • Should more time be allocated for the experiment?