Gold has a density of 19.3 g/cm'. Find the volume, in cubic centimeters, of a sample of gold that weighs 0.715 kg.

37.05 cm³

Explanation:

0.715 kg = (0.715 × 1000) g = 715g

volume = mass/density = 715/19.3 = 37.05 cm³

Atoms present per cm³ of Ag =

Unit cells which are present per cubic centimeter of W =

Volume =

Edge length =

Explanation:

Given that:-

The density of the solid W = 19.3 g/cm³

Molar mass of W = 183.84 g/mol

So, Moles present per cm³ of Ag = =0.105 mol/cm³

Also, 1 mole = atoms.

So,  

Atoms present per cm³ of Ag =

Thus, answer =

In BCC, the number of atoms  in the unit cell = 2

So,

Unit cells which are present per cubic centimeter of W =

Unit cells which are present per cubic centimeter of W =

The reciprocal of the unit cell/cm³ is the volume of the unit cell.

So,

Volume =

Also, Volume =

Thus, edge length = =

Edge length =

Atoms present per cm³ of Ag =

Unit cells which are present per cubic centimeter of W =

Volume =

Edge length =

Explanation:

Given that:-

The density of the solid W = 19.3 g/cm³

Molar mass of W = 183.84 g/mol

So, Moles present per cm³ of Ag = =0.105 mol/cm³

Also, 1 mole = atoms.

So,  

Atoms present per cm³ of Ag =

Thus, answer =

In BCC, the number of atoms  in the unit cell = 2

So,

Unit cells which are present per cubic centimeter of W =

Unit cells which are present per cubic centimeter of W =

The reciprocal of the unit cell/cm³ is the volume of the unit cell.

So,

Volume =

Also, Volume =

Thus, edge length = =

Edge length =

1. A. Group 1

2. B. A chemical change occurred which is evidenced by the change in color of the solution.

3. D. Physical change because the chemical properties of the salt and water remained the same.

4. D. Sphere B will float because it is less dense than water.

5. C. Shredding them into smaller pieces.

6. A. Her model uses eleven white pom-poms.

   B. Her model uses twelve black pom-poms.

   E. Her model uses eleven yellow pom-poms.

7.  B. The liquids have different densities.

8.  D. Physical Properties: color, texture Chemical Properties: ability to rust

9.  A. Container A will have 1 liter of helium, and container B will have 1 liter of water.

Explanation:

1.

In the periodic table, rows represent the period that they are in, while columns represent the groups that elements are in. Elements in the same group (column) share similar properties. Since Sodium (Na) is found in group 1, elements that are similar in properties would be found in the same group.

2.  

A chemical change is marked with a change in color, production of gas, heat, and sometimes smell and light. A chemical change results in new products formed, in which the properties and identities of the reactants change as well because their atoms were rearranged. In this case, the change in color of solution shows that a chemical change had occurred.

3.

Earlier we said that chemical change results in new products, for physical change it does not. The substance will keep its identity. Like in the scenario, the salt and water did mix together, but when they were separated through evaporation, the salt retained its identity and so did the water. The substances involved merely changed phases. So this was a physical change.

4.

If the density of the object is more than the density of the liquid, the object will sink. On the other hand, if the density of the object is less than the density of the liquid, it will float.

If water has a density of 1g/cm³, the object that has the lesser density will float. First you solve for the densities of each object and it can be computed using the formula:

D = m/v

where D = density; m = mass; and v = volume

Sphere A:

Sphere B:

So as you can see, only Sphere B has a density less or is less dense than water, so only Sphere B will float.  

5.

The groundskeeper shredding leaves is an application of physical change. As you can see, the identity of the leaves would be the same if you just shred them. Even if they change in shape and size, the leaves are still leaves, only smaller.

6.

A stable atom has the same number of electrons and protons. The number of protons is represented by the atomic number of an element.

Sodium has an atomic number of 11. This means that there are 11 protons (yellow pom poms) in a sodium atom. Since it is stable, you can also say that there are 11 electrons (White pom poms) as well.  

The number of neutrons can be determined by taking a look at the mass number of an atom. The mass number of sodium is 23. The mass number is the number of protons and neutrons combined.

23 = p + n

23 = 11 + n

23 - 11 = n

12 = n

The number of neutrons would be 12 (black pom poms).

7.

When two liquids do not mix, this means they are immiscible. The layers are formed because of the difference in density. Remember earlier about density and an object or substance's ability to float? Well it applies here too. The liquid on top is less dense than the one below it, so it floats up and the denser liquid sinks.

8.

Physical properties are things that you can observe using your senses. Chemical properties are properties that you can only observe when chemical structure is changed.

Seat cover has a smooth texture.  

Physical because it was determined by touch.

The front basket of the bike is purple.

Physical because it was determined by sight.

The bike is rusted.

Chemical because the metal changed its chemical structure as a result of a reaction.

9.

The sealed containers represent a closed system, or a vacuum where nothing goes in or out. In a closed system, just remember that matter is not created, nor destroyed. Simply put, this means that whatever it started with is what will it end up with.

In container A you have 1 L of helium gas, so since the container is sealed, none escaped. This means that you will end up with the same amount of helium gas as you did before. The same goes for the 1L of water in container B.  

1. The correct option is A.

The periodic table of element is divided into two distinct groups, which are group and periods. The group refers to those elements that are found in the same vertical column; they are also called family. The period refers to those elements that are found in the same horizontal rows.

Elements in the same group typically have similar chemical and physical properties. This is due to the fact that they have similar number of electrons in their valence shells.

Since sodium is found in group one of the periodic table, other elements that have properties that are similar to that of sodium will also be found in group 1. These elements include: lithium, potassium, rubidium, caesium and francium.

2. The correct option is B

In chemistry, there are two types of changes, these are physical and chemical change. In physical change the substances involved retained their  identity while in chemical change, the substances involved are changed into another substances.

In this question, we are told that copper sulphate react with iron shavings. During the process, the iron shaving dissolved in copper sulphate (which is colour blue) and the whole solution turn to green. Apart from the change in colour of the solution, a new product, which is iron sulphate is also produced. This changes indicate that, the change involved in the reaction is a CHEMICAL CHANGE.

3. The correct option is D.

Looking at the procedure involved in this question, you will observed that all the changes that took place are physical changes.

Grinding of salt into fine powder, dissolving it in water, increasing is solubility by heating and evaporating the liquid are all physical changes. The change is described as physical because the identity of the salt is retained all through the process.

4. The correct option is D.

The density of a substance refers to the ratio of the mass and the volume of the substance.

Mathematically, density = mass / volume.

We are given two spheres in the question, we have to find their densities in order to determine whether their densities is higher or lower than that of water.

Density of Sphere A = mass / volume = 24 /19.4 = 1.24 g/cm

Density of Sphere B = mass / volume = 13.6 / 17 = 0.80 g/cm

Looking at the densities of the two spheres, we observe that the density of sphere B is less that that of water, which is 1 g /m.  Therefore, sphere B will float in water because its density is less than that of water.

Sphere A will sink in water because it is denser than water.

5. The correct option is C.

Physical change is a type of change in which a substance retains its identity, that is, there is no change in its chemical properties. Looking at the options given in this question, you will observe that shredding of leaves only reduce their sizes, it does not affect their chemical properties at all, thus, shredding is a physical change. The other options given are examples of chemical changes.

6. The correct options are A, B AND E.

The element sodium has atomic number of 11 and atomic mass of 23. This implies that, it has 11 electrons, 11 protons and 12 neutrons (23 - 11).

In the question, we are told that colour white represents electrons, black represent neutrons and yellow represent protons, so we have:

Electrons = White pom poms = 11

Protons = Yellow pom poms = 11

Neutrons = Black pom poms = 12

Thus, her model have 11 white pom poms, 12 black pom poms and 11 yellow pom poms (These correspond to options A, B AND E).

7. The correct option is B.

Two liquids are described as immiscible when the two of them can not mix together. Two different liquids will not be able to mix together if their densities are different, that is one is lighter while the other one is denser. The liquid that is denser will sink and stay at the bottom of the container while the liquid that is lighter will float. Thus, the two liquids form two distinct layers because they have different densities.

8. The correct option is D.

The smooth texture and the change in colour of the front basket that Gracie observed are examples of physical changes. This is because, these changes does not affect the chemical properties of the substances. The rusting that Gracie observed is an example of chemical change. This is because rusting involves the chemical mixing of iron and air in the presence of water, leading to the formation of a new product called rust (hydrated iron lll oxide).

9. The correct option is A.

A sealed container represent a vacuum, a closed system. A close system refers to an isolated system that is not in contact with other systems. If the balloons burst inside the sealed containers, they will still be containing the original amount of air and liquid that was put inside them. Thus, container A will have one liter of helium and container B will have one liter of liquid water.

1. A. Group 1

2. B. A chemical change occurred which is evidenced by the change in color of the solution.

3. D. Physical change because the chemical properties of the salt and water remained the same.

4. D. Sphere B will float because it is less dense than water.

5. C. Shredding them into smaller pieces.

6. A. Her model uses eleven white pom-poms.

   B. Her model uses twelve black pom-poms.

   E. Her model uses eleven yellow pom-poms.

7.  B. The liquids have different densities.

8.  D. Physical Properties: color, texture Chemical Properties: ability to rust

9.  A. Container A will have 1 liter of helium, and container B will have 1 liter of water.

Explanation:

1.

In the periodic table, rows represent the period that they are in, while columns represent the groups that elements are in. Elements in the same group (column) share similar properties. Since Sodium (Na) is found in group 1, elements that are similar in properties would be found in the same group.

2.  

A chemical change is marked with a change in color, production of gas, heat, and sometimes smell and light. A chemical change results in new products formed, in which the properties and identities of the reactants change as well because their atoms were rearranged. In this case, the change in color of solution shows that a chemical change had occurred.

3.

Earlier we said that chemical change results in new products, for physical change it does not. The substance will keep its identity. Like in the scenario, the salt and water did mix together, but when they were separated through evaporation, the salt retained its identity and so did the water. The substances involved merely changed phases. So this was a physical change.

4.

If the density of the object is more than the density of the liquid, the object will sink. On the other hand, if the density of the object is less than the density of the liquid, it will float.

If water has a density of 1g/cm³, the object that has the lesser density will float. First you solve for the densities of each object and it can be computed using the formula:

D = m/v

where D = density; m = mass; and v = volume

Sphere A:

Sphere B:

So as you can see, only Sphere B has a density less or is less dense than water, so only Sphere B will float.  

5.

The groundskeeper shredding leaves is an application of physical change. As you can see, the identity of the leaves would be the same if you just shred them. Even if they change in shape and size, the leaves are still leaves, only smaller.

6.

A stable atom has the same number of electrons and protons. The number of protons is represented by the atomic number of an element.

Sodium has an atomic number of 11. This means that there are 11 protons (yellow pom poms) in a sodium atom. Since it is stable, you can also say that there are 11 electrons (White pom poms) as well.  

The number of neutrons can be determined by taking a look at the mass number of an atom. The mass number of sodium is 23. The mass number is the number of protons and neutrons combined.

23 = p + n

23 = 11 + n

23 - 11 = n

12 = n

The number of neutrons would be 12 (black pom poms).

7.

When two liquids do not mix, this means they are immiscible. The layers are formed because of the difference in density. Remember earlier about density and an object or substance's ability to float? Well it applies here too. The liquid on top is less dense than the one below it, so it floats up and the denser liquid sinks.

8.

Physical properties are things that you can observe using your senses. Chemical properties are properties that you can only observe when chemical structure is changed.

Seat cover has a smooth texture.  

Physical because it was determined by touch.

The front basket of the bike is purple.

Physical because it was determined by sight.

The bike is rusted.

Chemical because the metal changed its chemical structure as a result of a reaction.

9.

The sealed containers represent a closed system, or a vacuum where nothing goes in or out. In a closed system, just remember that matter is not created, nor destroyed. Simply put, this means that whatever it started with is what will it end up with.

In container A you have 1 L of helium gas, so since the container is sealed, none escaped. This means that you will end up with the same amount of helium gas as you did before. The same goes for the 1L of water in container B.