Subscribe

8th grade · Science · Unit 9 of 13

Water, Acids & Bases

Cohesion, adhesion and surface tension, and the pH scale.

What your child practices

Practices the properties of water (cohesion, adhesion and surface tension) and the everyday things they explain, and comparing acids and bases, including their pH relative to pure water.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: 8.6(C); 8.6(D) · cohesion, adhesion and surface tension in water, and the properties and pH of acids and bases

How we explain it

Children can open this short lesson before they practice.

  1. Water molecules stick to each other (cohesion) and to other things (adhesion), which makes surface tension.
  2. pH below 7 is acidic, 7 is neutral (pure water), above 7 is basic. Lower pH is more acidic.
  3. Bases turn red litmus blue; acids turn blue litmus red.

Example: Which is more acidic: pH 3 or pH 6? Lower pH means more acidic. 3 is lower than 6. Answer: pH 3

Water, Acids & Bases in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 9 of 13 in 8th grade Science, after Natural Selection and before Stars, Galaxies & the Universe.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Texas Education Agency (TEA)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Water molecules sticking to each other is called…

    • evaporation
    • density
    • cohesion
    • adhesion

  2. Question 2

    A paper towel soaks up a spill because of…

    • acidity
    • adhesion and cohesion
    • density only
    • magnetism

  3. Question 3

    A substance with a pH below 7 is…

    • salty only
    • basic
    • acidic
    • neutral

  4. Question 4

    Red litmus paper turns blue in…

    • an acid
    • pure water
    • a base
    • vinegar

  5. Question 5

    A water strider can walk on a pond because of…

    • acidity
    • surface tension
    • adhesion to its legs
    • buoyancy only

  6. Question 6

    Each step down the pH scale is ten times more acidic. pH 4 is how many times more acidic than pH 5?

    • 1
    • 2
    • 100
    • 10

More 8th grade