Question

marco wants to investigate the chemical properties of sodium bicarbonate, or baking soda. he plans to carry out the tests below.
test 1: mix a teaspoon of sodium bicarbonate into a cup of warm water to see if it dissolves.
test 2: mix a teaspoon of sodium bicarbonate into a cup of vinegar to see if it fizzes.
test 3: heat a teaspoon of sodium bicarbonate in the oven to see if its melting point is less than 400 degrees fahrenheit.
which statement provides the best assessment of his tests?
only test 3 will indicate a chemical property of sodium bicarbonate. tests 1 and 2 will show a physical property of the substance.
only tests 1 and 2 will indicate chemical properties of sodium bicarbonate. test 3 will show a physical property of the substance.
only test 2 will indicate a chemical property of sodium bicarbonate. tests 1 and 3 will show a physical property of the substance.
only tests 1 and 3 will indicate chemical properties of sodium bicarbonate. test 2 will show a physical property of the substance.

Explanation:

• Test 1: Dissolving sodium bicarbonate in water is a physical change. There is no new substance formed. Solubility is a physical property.
• Test 2: When sodium bicarbonate reacts with vinegar (\(CH_3COOH\)), a chemical reaction occurs: \(NaHCO_3+CH_3COOH = CH_3COONa + H_2O+CO_2\uparrow\). The fizzing is due to the production of carbon dioxide gas. This indicates a chemical property (reactivity with acids).
• Test 3: Measuring the melting point is a physical property measurement. Melting point is a characteristic of a substance's physical state change (from solid to liquid) without a change in chemical composition.

Answer:

Only Test 2 will indicate a chemical property of sodium bicarbonate. Tests 1 and 3 will show a physical property of the substance.