Quiz For Grade - 7 On Chemistry- Chapter 5 - Acids, Bases & Salts

Acidic substances taste sour because they release hydrogen ions when dissolved in water. These hydrogen ions stimulate the taste buds on our tongue, which are sensitive to acidic flavors. Sour taste is often associated with fruits like lemons, limes, and oranges, as well as vinegar and certain dairy products like yogurt.

Neutralization is a chemical reaction between an acid and a base, resulting in the formation of a salt and water. During neutralization, heat is also released as an exothermic reaction. Therefore, the correct answer is "All of the above" because neutralization gives out heat, water, and salt.

Basic substances taste bitter because they have a higher pH level. Bitter taste receptors are sensitive to alkaline substances, which are typically found in basic substances. This is in contrast to sour taste, which is associated with acidic substances, and salty and sweet tastes, which are typically associated with neutral substances.

Oranges and lemons are known for their tangy and acidic taste, which is attributed to the presence of citric acid. Citric acid is a natural acid found in citrus fruits and is responsible for their sour flavor. It is commonly used as a flavoring agent in various food and beverage products due to its refreshing and tart taste.

Basic substances, such as soap or water, are often slippery to touch. This is because they reduce the friction between surfaces, making them feel smooth and causing objects to slide easily.

Formic acid is the correct answer because it is the acid that is commonly found in the sting of insects. This acid is responsible for the burning sensation and pain that is felt when stung by certain insects, such as ants and bees. Formic acid is produced by these insects as a defense mechanism, and it acts as a deterrent to potential predators. It is a strong acid with a pungent odor and can cause irritation and discomfort when it comes into contact with the skin.

Distilled water is considered a neutral substance because it has a pH level of 7, which is neither acidic nor basic. Distilled water is pure water that has been boiled and condensed, removing any impurities or minerals that could affect its pH level. As a result, it has a balanced concentration of hydrogen ions (H+) and hydroxide ions (OH-), making it neither acidic nor basic.

Sulphuric acid is known as the king of chemicals because it is one of the most widely used and important industrial chemicals. It has numerous applications in various industries, including manufacturing fertilizers, dyes, detergents, and pharmaceuticals. It is also commonly used in the production of batteries and as a laboratory reagent. Additionally, sulphuric acid is highly corrosive and has a strong acidic nature, making it a powerful and versatile chemical compound.

Sodium bicarbonate (NaHCO3), also known as baking soda, is a basic substance. When dissolved in water, it undergoes hydrolysis, producing hydroxide ions (OH-) which increase the pH of the solution. This basic nature is what gives sodium bicarbonate its ability to neutralize acids, making it useful in various applications like baking, cleaning, and as an antacid.

Turmeric changes color when in contact with a basic substance. This is because turmeric contains a compound called curcumin, which is a pH indicator. When curcumin comes into contact with a basic substance, it undergoes a chemical reaction that causes it to change color. Therefore, turmeric will not change color when in contact with neutral or acidic substances, only with basic substances.