Baking soda or sodium bicarbonate is an ionic compound with the chemical formula NaHCO3. In water, it dissociates into two ions, Na+ and HCO3-, or sodium and bicarbonate ions. The bicarbonate ion is the conjugate base formed when a weak acid called carbonic acid gives up a hydrogen ion; as its conjugate base, bicarbonate can accept a hydrogen ion. This reaction decreases the hydrogen ion concentration in the water, making it more alkaline. The bottom line is this: if you want to make an alkaline solution for a simple science experiment, all you need to do is dissolve baking soda in water.
Measure out some baking soda. The more baking soda you add, the more alkaline your solution will be. Sodium bicarbonate is a rather weak base, so you can never make the solution as alkaline as you would with a stronger base such as sodium hydroxide.
Pour some water in the glass and add the baking soda. Stir until it dissolves.
Dip the pH paper into the solution to measure its pH. The pH paper kits generally come with a scale showing which colour matches which pH range; this way, you can get a rough estimate of how alkaline your solution is.
Dissolved baking soda acts as a weak antacid by neutralising a little HCl in your stomach if you drink it, although since it also contains sodium it increases your sodium intake.