Physical Properties
What property measures how much matter is in an object?
Mass.
What chemical property describes a substance’s ability to burn?
Flammability
Sharpening a pencil — physical or chemical change?
Physical change
Name one household liquid that can be used as invisible ink.
Lemon juice, milk, vinegar, or baking soda solution
What tool would you use to measure the length of a pencil?
Ruler or measuring tape
What happens when vinegar reacts with baking soda?
A chemical reaction occurs, producing carbon dioxide gas bubbles
Boiling water — physical or chemical change?
Physical change
Why does the writing disappear after drying?
The liquid mostly evaporates, leaving the paper looking blank
If a balloon inflates and takes up more space, which property are we observing?
Volume
Iron reacts with oxygen and water to form a reddish-brown substance. What is this process called?
Rusting
Frying an egg — physical or chemical change?
Chemical change
What makes the hidden message appear when heat is applied?
Heat causes sugars, acids, or proteins in the liquid to react with oxygen, producing a brown color (oxidation or caramelization)
Name two physical properties you can observe without touching the object.
Color, shape (or size, texture, temperature)
What is it called when a substance reacts with oxygen in the air and changes color, like a cut apple turning brown?
Oxidation
Cooking pasta involves both a physical and chemical change. Explain both.
Physical: pasta softens as it absorbs water. Chemical: starch in the pasta changes as it cooks
Is revealing a hidden message with heat a physical or chemical change? Why?
Chemical change — new brown substances form that weren’t there before
A solid chocolate bar melts in your hand. Is this a physical or chemical change, and why?
Physical change — it only changes state; no new substance is formed
Give an example of a chemical property that involves light.
Light sensitivity — chemicals change when exposed to light, e.g., photographic paper or glow-in-the-dark toys
A fireworks display produces light, sound, heat, and gas. Why is this a chemical change?
New substances are formed (gases, light-emitting compounds, heat), which cannot be reversed easily
Could you reverse the process after the message appears? Why or why not?
No — once the paper browns, you cannot turn it back into clear lemon juice or milk