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.
