Base — Science definition
A substance that decreases hydrogen-ion activity in water; common dilute basic solutions have pH above 7 near room temperature. Never identify unknown samples by touch or taste.
Where it is taught
- Acids, Bases & pH — Chemistry, Physical Science: Matter, Forces & Energy, Grade 8
In use
Neutralization involves an acid-base reaction, often producing water and dissolved salts in introductory examples.
Acids, Bases & pH
Questions using base
Problem 1
- orange juice (pH ≈ 3.5)
- black coffee (pH ≈ 5)
- drain cleaner (pH ≈ 13)
- milk (pH ≈ 6.5)
Answer and explanation
drain cleaner (pH ≈ 13)
A pH near 13 is far above 7, making drain cleaner a strong base.
Problem 2
Answer and explanation
7
New pH = 4 + 3 = 7, which is neutral.
Problem 3
- gas only
- salt
- new acid
- new base
Answer and explanation
salt
Neutralization reactions between an acid and a base produce water plus a salt.
Problem 4
Answer and explanation
No. Concentrations, reacting amounts, and acid/base chemistry matter. Equal volumes alone cannot establish the final pH or product safety.
No. Concentrations, reacting amounts, and acid/base chemistry matter. Equal volumes alone cannot establish the final pH or product safety.
Response criteria
- Use the supplied conditions and relevant evidence.
- Explain the scientific mechanism or calculation.
- State a meaningful limitation or testable next step.