Deep Freeze

What your child will figure out

• Locate and read negative integers below zero on a vertical number line.
• Compare signed temperatures or depths by using their relative height rather than digit size.
• Model addition of positive and negative integers as upward and downward moves.
• Model subtraction, including subtracting a negative, as movement opposite to the subtracted direction.

The levels

1. Read the cold

   Predict and dock at −4 below the zero ice shelf, then explain what the negative sign means.

2. Cross zero

   Move seven steps up from −5 to 2 and use height to compare the two positions.

3. Add a cold current

   Model −3 + (−4) as four downward moves and explain why adding a negative decreases the value.

4. Warm-water lift

   Add a positive integer while staying below zero and compare two negative endpoints by height.

5. Surface crossing

   Add upward across zero and continue counting into positive coordinates.

6. Balance the currents

   Recognize additive opposites by returning from 5 to exactly zero.

7. Drop the ballast

   Subtract a positive integer far enough to cross from positive to negative.

8. Deeper trench

   Subtract a positive integer from a negative start and explain why the result is lower.

9. Reverse the dive

   Subtract a negative from a positive start as an upward reversal.

10. Escape the ice lock

    Subtract a negative from below zero and cross into positive coordinates.

11. Recover lost depth

    Subtract a negative while remaining below zero, separating direction from sign of the result.

12. Master the storm

    Transfer the movement model across a longer subtract-negative crossing from −7 to 3.