Name:______Date:______
Chemistry-2 Period______
We are learning______
Chapter 1: Activity 3: Physical and Chemical Changes
PHYSICAL VS. CHEMICAL CHANGES
In a physical change, the original substance still exists, it has only changed form. The substance’s chemical identity has not changed. For example, a phase change (changing between solid, liquid, and gas) is a physical change.
In a chemical change, a new substance is produced. The original substance is no longer present.
At the molecular level, a chemical change involves making or breaking of bonds between atoms. For example, iron rusting is a chemical change. The iron has reacted with oxygen, and the original iron metal is changed. It now exists as iron oxide, a different substance.
1. Underline the word that helps identify whether a chemical or physical change is occurring.
2. Classify the following changes as either chemical or physical by putting a check in the appropriate column.
PHYSICALCHANGE / CHEMICAL
CHANGE
1. Sodium Hydroxide (NaOH) dissolves in water (H2O).
2. Hydrochloric acid (HCl) reacts with potassium hydroxide (KOH) to produce salt, water and heat.
3. A pellet of sodium (Na) is sliced inn two.
4. Water is heated and changed to steam.
5. Potassium chlorate (KClO4) decomposed to potassium chloride (KCl) and oxygen gas (O2).
6. Iron (Fe) bumpers on a car rust.
7. When placed in H2O, a sodium pellet catches fire as hydrogen gas (H2) is liberated (released) and sodium hydroxide (NaOH) forms.
8. Water evaporates from a pool.
9. Ice (H2O) melts in a cup of soda.
10. Milk begins to sour because it has been left outside.
11. Sugar (C12H22O11) dissolves in hot tea.
12. Rotting wood is found in the forest.
13. Pancakes cooking on a griddle.
14. Grass growing in a lawn.
15. A tire is inflated with air.
16. Food is digested in the stomach.
17. Water is absorbed by a paper towel.