You accidentally left a carton of milk on the counter all night. You notice that the milk tastes sour compared to the way it tastes when it is stored in the refrigerator overnight.

1. Is this observation testable?

2. Determine whether the observation is qualitative or quantitative.

3. Write a hypothesis and null hypothesis.

4. What are the independent and dependent variables?

5. What are the controls (both positive and negative) ?

Yes, this observation is testable because you can do the experiment with your own controlled conditions and see if this with the milk would happen again.

It is qualitative observation because you use your senses such as sight, smell, touch, taste or hear to observe the results (in quantitative observations you use instruments for measurement).

Null hypothesis: The taste of the milk is the same when it is left on the counter (warm) and when it is left in the refrigerator (cold) or simply saying the place where we put milk doesn't affect the milk taste

Hypothesis: The milk left on the counter is sour due to acidification of milk via bacteria that works on warmer place.

Independent variable (changed by a scientist in order to affect the dependent one) is a place where we put milk (temperature).

Dependent variable is milk (milk taste).