Basic Chemistry Exam - Summer School

1. This is the fomula for vinegar.

CH₃CO₂H

What are all of the elements found in the formula for vinegar?

Hydrogen and Oxygen

Carbon, Hydrogen, and Oxygen

Carbon and Oxygen

Chrome, Cobalt, and Hydrogen

The formula for vinegar, CH3CO2H, indicates the presence of carbon, hydrogen, and oxygen. The "C" represents carbon, the "H" represents hydrogen, and the "O" represents oxygen.

Explanation

The formula for vinegar, CH3CO2H, indicates the presence of carbon, hydrogen, and oxygen. The "C" represents carbon, the "H" represents hydrogen, and the "O" represents oxygen.

2. Which of the following is an example of a physical change?

Ice forming after water is placed in a freezer.

A certain liquid is added to a solid, and bubbles of gas form.

Adding baking sode to vinegar.

A bicycle rusting in the rain.

Ice forming after water is placed in a freezer is an example of a physical change because the water molecules rearrange themselves and slow down their movement to form a solid structure. The substance itself remains the same, only changing its state from a liquid to a solid. No new substances are formed, and the chemical composition of water remains unchanged.

Explanation

Ice forming after water is placed in a freezer is an example of a physical change because the water molecules rearrange themselves and slow down their movement to form a solid structure. The substance itself remains the same, only changing its state from a liquid to a solid. No new substances are formed, and the chemical composition of water remains unchanged.

3. What element is represented in the picture?

Carbon

Boron

Oxygen

Helium

The correct answer is Oxygen. Oxygen is represented in the picture.

Explanation

The correct answer is Oxygen. Oxygen is represented in the picture.

4. When the scientist Mendeleev made his arrengement of the periodic table, he found that elements with _______________________ fell into the same group on the table.

The same mass

Similar size

The same color

Similar properties

When Mendeleev arranged the periodic table, he observed that elements with similar properties fell into the same group. This means that they exhibited similar chemical behaviors, reactions, and characteristics. The arrangement of elements based on their similar properties allowed for the identification of trends and patterns in the periodic table, which facilitated the prediction of the properties of undiscovered elements.

Explanation

When Mendeleev arranged the periodic table, he observed that elements with similar properties fell into the same group. This means that they exhibited similar chemical behaviors, reactions, and characteristics. The arrangement of elements based on their similar properties allowed for the identification of trends and patterns in the periodic table, which facilitated the prediction of the properties of undiscovered elements.

5. Which of the following changes is a chemical change?

Water is boiled.

Wood is burned.

Aluminum foil is crumpled.

Glass is shattered.

Wood is burned is the correct answer because burning wood involves a chemical reaction known as combustion. During combustion, the wood undergoes a chemical change, breaking down into different substances such as carbon dioxide, water vapor, and ash. This is different from the other options which involve physical changes, such as boiling water, crumpling aluminum foil, or shattering glass, where the substances involved do not change their chemical composition.

Explanation

Wood is burned is the correct answer because burning wood involves a chemical reaction known as combustion. During combustion, the wood undergoes a chemical change, breaking down into different substances such as carbon dioxide, water vapor, and ash. This is different from the other options which involve physical changes, such as boiling water, crumpling aluminum foil, or shattering glass, where the substances involved do not change their chemical composition.

6. When you mix sodium hydroxide and bromothymol blue, it becomes warm. This is an example of a _________________ reaction.

Exothermic

Inhibitor

Endothermic

Think to yourself - is there any information in the problem that you don't need? Don't let big words confuse you - you may not need them!

Explanation

Think to yourself - is there any information in the problem that you don't need? Don't let big words confuse you - you may not need them!

7. The mass number of an atom is equal to the number of protons and neutrons. According to this definition, which element in the table above has the highest mass number?

Hydrogen

Carbon

Boron

Oxygen

The mass number of an atom is determined by the sum of its protons and neutrons. Oxygen has the highest mass number among the given elements because it has 8 protons and 8 neutrons, resulting in a mass number of 16. Hydrogen has a mass number of 1, carbon has a mass number of 12, and boron has a mass number of 11. Therefore, oxygen has the highest mass number.

Explanation

The mass number of an atom is determined by the sum of its protons and neutrons. Oxygen has the highest mass number among the given elements because it has 8 protons and 8 neutrons, resulting in a mass number of 16. Hydrogen has a mass number of 1, carbon has a mass number of 12, and boron has a mass number of 11. Therefore, oxygen has the highest mass number.