Chemical change vs. physical change: Understanding reactions for Grade 8

📚 What's the Difference?

Let's break down chemical and physical changes! They're all about how matter transforms. Physical changes are like re-arranging things without changing what they *are*, while chemical changes create entirely new substances. Think of it like this: a physical change is like re-arranging Lego bricks, while a chemical change is like baking a cake – you can't easily get the raw ingredients back!

🔬 Physical Change Explained

A physical change alters the form or appearance of a substance, but it doesn't change its chemical composition. The substance is still the same stuff, just in a different form.

• 🧊 Melting Ice: When ice melts into water, it's still $H_2O$. Just in a different state.
• ✂️ Cutting Paper: You're making smaller pieces, but it's still paper!
• dissolving Sugar When sugar dissolves in water the chemical composition remain unaltered.

• 🔥 Burning Wood: Wood combines with oxygen to create ash, smoke, and gases.
• 🍎 Rusting Iron: Iron reacts with oxygen and water to form rust (iron oxide).
• 🍳 Cooking an Egg: The egg's proteins change their structure when heated.

• 🧊 State Changes: 🌡️ Changes in state (solid, liquid, gas) are typically physical changes.
• 🔄 Reversibility: ↩️ Physical changes are generally easier to reverse than chemical changes. Think about freezing water back into ice!
• ✨ New Substances:** 🌟 If a new substance is formed, it's a chemical change. Bubbles forming (when not boiling), color changes, and precipitate formation can be indicators!