The researcher may first weight the beaker with water and then start to heat the water to a constant temperature, for example 30 °C and then start adding salt and stirring. He should add salt slowly until solid salt starts to become visible and the solution starts becoming cloudy. When this happens, he should quickly weigh the beaker. The increase in mass is the mass of salt dissolved at that temperature.
The procedure is then repeated but at an increased temperature until 5-6 temperatures have been tested.
The given question is incomplete. The complete question is :
In each row check off the boxes that apply to the underlined reactant. The underlined reactant acts as a... (check all that apply)
1. 
here underlined is 
A. Brønsted-Lowry acid
B. Brønsted-Lowry base
C. Lewis acid
D. Lewis base
2. 
Here underlined is 
A. Brønsted-Lowry acid
B. Brønsted-Lowry base
C. Lewis acid
D. Lewis base
3. 
Here underlined is 
A. Brønsted-Lowry acid
B. Brønsted-Lowry base
C. Lewis acid
D. Lewis base
Answer: 1. Brønsted-Lowry acid
2. Lewis base
3. Brønsted-Lowry base
Explanation:
According to the Bronsted Lowry conjugate acid-base theory, an acid is defined as a substance which donates protons and a base is defined as a substance which accepts protons.
According to the Lewis concept, an acid is defined as a substance that accepts electron pairs and base is defined as a substance which donates electron pairs.
1. 
As
is donating a proton , it acts as a bronsted acid.
2. 
As
contains a lone pair of electron on nitrogen , it can easily donate electrons to
and act as lewi base.
3. 
As
is accepting a proton , it acts as a bronsted base.
Answer: a single compound
Explanation: I know it