Chemical and Physical Changes Worksheet for 11-Year-Olds | 20 Questions with Problem Solving

Instructions

Read the descriptions below to understand the difference between physical and chemical changes. Then, answer the questions that follow.

• A physical change is a change in the form or appearance of a substance, but not what it's made of. The substance is still the same, just in a different shape or state (like solid, liquid, or gas). Most physical changes are reversible. Clues: Change in size, shape, or state of matter (melting, freezing, boiling).
• A chemical change (also called a chemical reaction) is a change that results in a completely new substance with different properties. You cannot easily get the original substance back. Clues: A new color appears, a gas is produced (bubbles), light or heat is given off, a new smell is created, a solid forms from liquids.

Part 1: Identify the Change

For each example below, decide if it is a physical change or a chemical change. Write your answer on the line.

1. Melting an ice cube: _________________________
2. Baking a cake from batter: _________________________
3. Chopping a carrot into small pieces: _________________________
4. A bicycle chain rusting: _________________________
5. Boiling water to make steam: _________________________
6. A firework exploding in the sky: _________________________
7. Crumpling a piece of paper: _________________________
8. Digesting your lunch: _________________________
9. Mixing salt and water until the salt dissolves: _________________________
10. Burning a log in a fireplace: _________________________

Part 2: Problem-Solving Scenarios

Read each scenario carefully. Identify the type of change and explain your reasoning using the clues from the instructions.

11. A chef first chops an apple into slices and then bakes the slices in a pie. The apples become soft and brown. Which part of this process is a physical change and which is a chemical change?
    Explain your answer:
    
    
    
12. You leave a glass of ice-cold water on the table on a humid day. Soon, you see little drops of water forming on the outside of the glass. Is this a physical or chemical change?
    Explain your answer:
    
    
    
13. To make a fizzy drink, you drop a tablet into a glass of water. It immediately starts bubbling and dissolves. What kind of change is this, and what is your biggest clue?
    Explain your answer:
    
    
    
14. A candle is lit. The wax near the flame melts and drips down the side, where it becomes solid again. The wick, however, turns black and burns away. Describe the physical change AND the chemical change happening.
    Explain your answer:
    
    
    
15. You mix yellow and blue paint together to make green paint. Is making green paint a physical or chemical change?
    Explain your answer:
    
    
    
16. A piece of bread is left in the toaster too long. It turns black and creates a burnt smell. What kind of change has occurred to the bread?
    Explain your answer:
    
    
    
17. You make a salad by tossing together lettuce, tomatoes, and cucumbers. Is making the salad a physical or chemical change?
    Explain your answer:
    
    
    
18. During a science experiment, you mix two clear liquids together. The mixture instantly becomes cloudy and a white solid settles at the bottom of the beaker. What is your evidence that a chemical change occurred?
    Explain your answer:
    
    
    
19. You crack an egg (a liquid) into a hot frying pan. The egg turns white and becomes solid. Can you cool the egg to turn it back into a liquid? What kind of change is this?
    Explain your answer:
    
    
    
20. A sculptor carves a statue out of a block of marble. Has the marble undergone a physical or chemical change?
    Explain your answer:
    
    
    

Answer Key

Part 1: Identify the Change

1. Physical change (The water just changed state from solid to liquid).
2. Chemical change (Baking causes chemical reactions, creating a new substance - the cake).
3. Physical change (The carrot is just in smaller pieces, it's still a carrot).
4. Chemical change (Rust is a new substance, iron oxide, formed from iron and oxygen).
5. Physical change (The water just changed state from liquid to gas).
6. Chemical change (The explosion involves rapid chemical reactions that produce light, heat, and sound).
7. Physical change (The paper has a new shape, but it's still paper).
8. Chemical change (Acids and enzymes in your body break food down into new substances).
9. Physical change (The salt is dissolved but is still present; you can get it back by evaporating the water).
10. Chemical change (Burning creates new substances like ash, smoke, and carbon dioxide).

Part 2: Problem-Solving Scenarios

11. Physical change: Chopping the apple. Chemical change: Baking the apple.
    Explanation: Chopping only changes the apple's shape. Baking causes chemical reactions that change the apple's texture, color, and taste, creating new substances.
12. Physical change.
    Explanation: This is condensation. Water vapor (a gas) from the air cooled on the glass and changed its state to liquid water. It's still water.
13. Chemical change.
    Explanation: The biggest clue is the bubbling, which shows a gas is being produced. This is a sign of a chemical reaction.
14. Physical change: The wax melting and re-solidifying. Chemical change: The wick burning.
    Explanation: The wax is only changing its state (solid to liquid and back). The wick is burning (combustion), which is a chemical reaction that produces light, heat, and smoke.
15. Physical change.
    Explanation: The two colors of paint are just mixed together. No new substance is formed. You could theoretically separate them again (though it would be very difficult).
16. Chemical change.
    Explanation: The bread has been burned (combustion). The clues are the change in color to black (carbon) and the new, burnt smell. The original bread is gone.
17. Physical change.
    Explanation: The vegetables are only mixed together. Each piece is still the same substance it was before (lettuce is still lettuce, etc.). No new substances were created.
18. Chemical change.
    Explanation: The evidence is the formation of a solid (called a precipitate) when two liquids were mixed. This shows a new substance was created.
19. Chemical change.
    Explanation: You cannot cool the egg to turn it back into a liquid. The heat caused the proteins in the egg to change permanently, creating a new substance (a cooked egg). This is not easily reversible.
20. Physical change.
    Explanation: The sculptor only changed the shape and size of the marble block. The substance itself is still marble.