Phase Changes in Everyday Life (Part 2)

What You'll Learn

The law of definite proportions states that a compound always contains the same elements in the same ratio by mass. Water is always 11.2% hydrogen and 88.8% oxygen.

Key Words

temperature
melting point

Materials Needed

plastic bottles
balloons
measuring cups
paper towels
thermometer

Safety First

Do not taste any materials.
Wear safety goggles when mixing liquids.

Steps

Step 1 — Read

Read and learn: The law of definite proportions states that a compound always contains the same elements in the same ratio by mass. Water is always 11.2% hydrogen and 88.8% oxygen.

Step 2 — Do

Build your model using the materials provided.

Step 3 — Observe

Compare the before and after states.

Step 4 — Record

Write your conclusion: did the results match your hypothesis?

Check Your Understanding

Question 1

1 of 3

Which is a sign of a chemical change?