Physical & Chemical Properties
Define physical property
A characteristic that can be observed without changing the substance.
What type of elements form ionic bonds?
Metals and nonmetals (between a metal and nonmetal)
Define a chemical reaction
When substances interact to form new substances
What is the law of conservation of mass?
Mass is conserved in a reaction
Name one sign of a chemical change.
Change in color, gas formation, precipitate, temperature change.
Give an example of a chemical property.
Flammability (ability to burn).
Give an example of a covalent compound.
Water (H₂O) or Carbon Dioxide (CO₂).
What is a reactant?
A substance that enters a chemical reaction.
Balance this equation: H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
What is a precipitate?
A solid that forms when two liquids react.
Explain why boiling water is a physical change.
The water changes state but remains H₂O.
Why do ionic compounds have high melting points?
Strong electrostatic forces between ions.
How do catalysts speed up a reaction?
They lower activation energy.
What are the reactants and products in rust formation?
Reactants = iron + oxygen; Product = iron oxide.
How does temperature change indicate a chemical reaction?
Energy is absorbed or released, causing heating or cooling.
Why is rusting considered a chemical change?
Rust forms when iron reacts with oxygen, producing a new substance (iron oxide).
Explain why sugar dissolves in alcohol but not in water.
Sugar is covalent; alcohol has similar polarity, so it dissolves.
What factors affect the reaction rate?
Temperature, concentration, surface area, and catalysts.
How is energy involved in breaking molecular bonds?
Energy is required to break bonds and released when new ones form.
Give an example of a chemical reaction that produces gas bubbles.
Vinegar + baking soda → CO₂ bubbles
Describe a situation where both a physical and chemical change happen.
Cooking—melting butter (physical), breaking down proteins (chemical).
Describe the difference in conductivity between ionic and covalent compounds.
Ionic compounds conduct electricity in water, covalent compounds do not.
Explain why photosynthesis is a chemical reaction.
It transforms CO₂ and water into glucose and oxygen.
What happens to the atoms in a reaction?
They rearrange but are not created or destroyed.
Why is cooking an egg a chemical change?
Proteins break down and new substances form.