Properties and Structure of Matter Assessment

1. An atom of gold has an atomic number of 79 and a mass number of 197. How many neutrons does a gold atom contain?

79

197

118

276

To find the number of neutrons in an atom, subtract the atomic number from the mass number. The atomic number of gold is 79, which indicates the number of protons, and the mass number is 197, which is the total of protons and neutrons. Therefore, the number of neutrons can be calculated as follows: 197 (mass number) - 79 (atomic number) = 118 neutrons. This calculation reveals that a gold atom contains 118 neutrons.

Explanation

To find the number of neutrons in an atom, subtract the atomic number from the mass number. The atomic number of gold is 79, which indicates the number of protons, and the mass number is 197, which is the total of protons and neutrons. Therefore, the number of neutrons can be calculated as follows: 197 (mass number) - 79 (atomic number) = 118 neutrons. This calculation reveals that a gold atom contains 118 neutrons.

2. Which of the following best distinguishes a compound from a mixture?

A compound can be separated by physical means, while a mixture cannot

A compound is chemically combined and cannot be easily separated, while a mixture retains individual properties and can be separated

A mixture is made of one type of atom, while a compound contains multiple atom types

A compound is always homogeneous, while a mixture is always heterogeneous

A compound consists of two or more elements that are chemically bonded together, resulting in a substance with unique properties that cannot be separated by physical means. In contrast, a mixture contains two or more substances that are physically combined, allowing each component to retain its individual properties and be separated through physical methods, such as filtration or distillation. This distinction highlights the fundamental differences in the composition and separation methods of compounds and mixtures.

Explanation

A compound consists of two or more elements that are chemically bonded together, resulting in a substance with unique properties that cannot be separated by physical means. In contrast, a mixture contains two or more substances that are physically combined, allowing each component to retain its individual properties and be separated through physical methods, such as filtration or distillation. This distinction highlights the fundamental differences in the composition and separation methods of compounds and mixtures.

3. A student hammers a metal sheet into a thin foil without it breaking. Which property of matter is being demonstrated?

Conductivity

Solubility

Malleability

Density

Malleability is the property of a material that allows it to be deformed under compressive stress, enabling it to be hammered or rolled into thin sheets without breaking. In this scenario, the student successfully transforms a metal sheet into a thin foil, demonstrating that the metal is malleable. This characteristic is particularly prominent in metals, which can be shaped into various forms while maintaining their integrity, making malleability a key property in metalworking and manufacturing processes.

Explanation

Malleability is the property of a material that allows it to be deformed under compressive stress, enabling it to be hammered or rolled into thin sheets without breaking. In this scenario, the student successfully transforms a metal sheet into a thin foil, demonstrating that the metal is malleable. This characteristic is particularly prominent in metals, which can be shaped into various forms while maintaining their integrity, making malleability a key property in metalworking and manufacturing processes.

4. Match each scientist with their contribution to atomic theory.

J.J. Thomson

Ernest Rutherford

Niels Bohr

James Chadwick

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5. A substance has a mass of 45 g and occupies a volume of 15 cm³. What is its density?

3 g/cm³

675 g/cm³

0.33 g/cm³

60 g/cm³

Density is calculated using the formula: density = mass/volume. In this case, the mass of the substance is 45 g, and the volume is 15 cm³. By substituting these values into the formula, we get density = 45 g / 15 cm³, which simplifies to 3 g/cm³. This indicates that for every cubic centimeter of the substance, it has a mass of 3 grams.

Explanation

Density is calculated using the formula: density = mass/volume. In this case, the mass of the substance is 45 g, and the volume is 15 cm³. By substituting these values into the formula, we get density = 45 g / 15 cm³, which simplifies to 3 g/cm³. This indicates that for every cubic centimeter of the substance, it has a mass of 3 grams.

6. Which of the following are characteristics of a chemical change? (Select all that apply)

Formation of a precipitate

Change in shape or size

Emission of light or sound

Change in state

Production of gas

Color change indicating new substance formation

Chemical changes involve the transformation of substances into new ones, which is indicated by several characteristics. The formation of a precipitate signifies a new solid material emerging from a liquid solution. Emission of light or sound often accompanies reactions, indicating energy changes. Production of gas is a clear sign of a chemical reaction, as new gaseous products are formed. A color change typically indicates the formation of a new substance, highlighting the alteration of chemical properties. In contrast, changes in shape or size are physical changes, not chemical.

Explanation

Chemical changes involve the transformation of substances into new ones, which is indicated by several characteristics. The formation of a precipitate signifies a new solid material emerging from a liquid solution. Emission of light or sound often accompanies reactions, indicating energy changes. Production of gas is a clear sign of a chemical reaction, as new gaseous products are formed. A color change typically indicates the formation of a new substance, highlighting the alteration of chemical properties. In contrast, changes in shape or size are physical changes, not chemical.

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7. In the Bohr model, the electrons in the outermost energy level determine an atom's behavior during chemical reactions.

True

False

In the Bohr model, electrons occupy specific energy levels around the nucleus, with the outermost level, or valence shell, containing the electrons that are involved in chemical bonding. These valence electrons dictate how an atom interacts with others, influencing its reactivity and the types of bonds it can form. Therefore, the behavior of an atom during chemical reactions is primarily determined by the configuration and number of electrons in its outermost energy level.

Explanation

In the Bohr model, electrons occupy specific energy levels around the nucleus, with the outermost level, or valence shell, containing the electrons that are involved in chemical bonding. These valence electrons dictate how an atom interacts with others, influencing its reactivity and the types of bonds it can form. Therefore, the behavior of an atom during chemical reactions is primarily determined by the configuration and number of electrons in its outermost energy level.

8. The electrostatic force that maintains the structure of an atom works because ______ attracts electrons toward the nucleus, while electron-electron repulsion pushes electron pairs as far apart as possible.

Electrostatic attraction occurs due to the positive charge of protons in the nucleus, which pulls negatively charged electrons toward it. This force is essential for maintaining the structure of an atom, as it keeps electrons in orbit around the nucleus. Simultaneously, electron-electron repulsion arises from the like charges of electrons, causing them to repel each other and spread apart. This balance between attraction and repulsion is crucial for the stability and arrangement of electrons in an atom, ensuring that they occupy distinct energy levels without collapsing into the nucleus.

Explanation

Electrostatic attraction occurs due to the positive charge of protons in the nucleus, which pulls negatively charged electrons toward it. This force is essential for maintaining the structure of an atom, as it keeps electrons in orbit around the nucleus. Simultaneously, electron-electron repulsion arises from the like charges of electrons, causing them to repel each other and spread apart. This balance between attraction and repulsion is crucial for the stability and arrangement of electrons in an atom, ensuring that they occupy distinct energy levels without collapsing into the nucleus.

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Properties and Structure of Matter

1. An atom of gold has an atomic number of 79 and a mass number of 197. How many neutrons does a gold atom contain?

2.

What first name or nickname would you like us to use?

2. Which of the following best distinguishes a compound from a mixture?

3. A student hammers a metal sheet into a thin foil without it breaking. Which property of matter is being demonstrated?

4. Match each scientist with their contribution to atomic theory.

5. A substance has a mass of 45 g and occupies a volume of 15 cm³. What is its density?

6. Which of the following are characteristics of a chemical change? (Select all that apply)

7. In the Bohr model, the electrons in the outermost energy level determine an atom's behavior during chemical reactions.

8. The electrostatic force that maintains the structure of an atom works because ______ attracts electrons toward the nucleus, while electron-electron repulsion pushes electron pairs as far apart as possible.