Answer:
Through chemical reactions.
Explanation:
You tell if an unknown powder is salt, sugar, flour or baking soda by doing tests to see how the powder would react. For an example, baking soda in vinegar would cause it to fizzle, while flour would just make the vinegar murky and cloudy. With salt and sugar, you can test if it dissolves and if it does it is sugar. If not, it is salt.
