Properties of Water
What is the force called when water molecules stick to each other?
Cohesion
Is a substance with a pH of 3 an acid or a base?
Acid
Is oxygen (O₂) an element, compound, or mixture?
Element
In a reaction, do atoms get destroyed, created, or rearranged?
Rearranged)
What does the “pH” scale measure?
(Acidity/basicity of a solution)
Why can a paperclip “float” on water until soap is added?
(Surface tension from cohesion is broken
200 pts: What is the pH of pure water?
(7, neutral)
Is salt (NaCl) a compound or a mixture?
(Compound)
If 20 g of reactants are used, how many grams of products should form? (
20 g — law of conservation of mass)
Name one property of acids and one property of bases.
Acids: pH below 7, can be corrosive, turn blue litmus paper red
Bases: pH above 7, bitter taste, turn red litmus paper blue
Give an example of adhesion in everyday life.
Water sticking to glass, spiderweb, leaves)
Bases have a pH (higher/lower) than water.
Higher
300 pts: What’s the difference between homogeneous and heterogeneous mixtures?
Uniform vs Non-Uniform
Balance this: H₂ + O₂ → H₂O (
2H₂ + O₂ → 2H₂O)
Why is water called the “universal solvent”?
This happens because water is a polar molecule — its positive and negative ends can pull apart many other molecules (like salt or sugar).
Compare adhesion and cohesion in one sentence.
“Cohesion is when water molecules stick to each other, and adhesion is when water molecules stick to other surfaces.”
Give an example of a household acid and a household base.
Vinegar is a household acid, and baking soda is a household base.”
Explain why glucose (C₆H₁₂O₆) is a compound, not an element.
Because there is more than one type of atom.
Why is the number of atoms the same before and after a reaction?
(Mass is conserved — atoms rearrange)
Why is the number of atoms the same before and after a reaction?
(Mass is conserved — atoms rearrange)
💡 Question: Why does ice float on liquid water, and how does this property help life on Earth?
✅ Answer: Ice is less dense than liquid water because water expands when it freezes. This allows ice to float, which insulates lakes and ponds in winter, protecting aquatic life.
💡 Question: A solution has a pH of 2. Another solution has a pH of 5. How many times more acidic is the first solution than the second?
✅ Answer: 1,000 times more acidic, because each step on the pH scale is a power of 10.
💡 Question: Explain why salt water is considered a mixture and not a compound.
✅ Answer: In salt water, the salt and water are physically combined but not chemically bonded. The salt can be separated again by evaporation, so it’s a mixture.
💡 Question: A student burns 10 g of magnesium in a closed container with oxygen. The product is 16 g of magnesium oxide. Explain why this supports the law of conservation of mass.
✅ Answer: The mass of the reactants (10 g magnesium + 6 g oxygen) equals the mass of the product (16 g magnesium oxide). No mass is lost; it just rearranged.
💡 Question: Why is photosynthesis considered one of the most important chemical reactions on Earth?
✅ Answer: It uses sunlight to turn carbon dioxide and water into glucose and oxygen, providing food for plants and oxygen for animals — essential for life.