CHEMISTRY

EASY

1. Which of the following is an extensive property?a. Massb. Boiling pointc. Textured. Density

Answer: a

Extensive property is a property that depends on the amount of matter.

2. Who proposed the plum-pudding model which describes atom as having embedded electrons in a uniform, positively charged proton?a. Ernest Rutherfordb. Jhoseph John Thomsonc. Neil Bohrd. James Chadwick

Answer: b

Plum pudding model or the raisin bread model of atom was proposed by JJ Thomson after his experiment using cathode ray tube a forerunner of a television.

3. What is the SI unit for volume? a. Massb. Gramc. Literd. Cubic meter

Answer: c

Mass is not a unit but a base quantity,

4. Different substances have different density. Density is the mass of a substance divided by its volume. Which of the following substances is the densest?a. Alcoholb. Waterc. Mercuryd. Table salt

Answer: c

Mercury has a density of13.6 g/cm3, table salt has 2.2 g/cm3, water has 1.1 g/cm3. And the Alcohol has 0.79 g/cm 3 .

5. Periodic table is the tabular arrangement of the elements. How many period a periodic table has?

a. 7b. 10c. 13d. 18

Answer: 7

Period is the horizontal rows while group or family is the vertical column of periodic table. There are 7 periods and 18 groups.

AVERAGE

1. Through experiment scientists provide evidences to support their hypothesis. Which of the following evidences provides qualitative data?a. The presence of bubbles was observed after the reaction.b. The volume of the substance increases.c. The change in temperature indicates chemical changed. There are more number of germinated seed in the setup that is

exposed to sunlight

Answer: a

2. Chlorine was used as a weapon during the First World War. It has atomic number of 17. What is the maximum number in the third energy level?a. 8b. 10c. 18d. 20

Answer: c

To get the number of maximum number of electron in an energy level the formula to be used is 2n2 where n is the number of energy level. 2(32) is 18.

3. A bus travels with a constant speed of 30m/s in a straight road. What is the acceleration of the bus?

Answer: 0m/s2

Acceleration is the change in speed over change in time. The speed and the direction of the bus did not change therefore zero acceleration.

4. How do you compare the density of the Earth’s crust, mantle, and core?

a. The mantle is less dense than the core but denser than the crust.b. The mantle is less dense than both the core and the crust.c. The mantle is denser than the core but less dense than the crust.d. The mantle is denser than both the core and the crust

answer: A

DIFFICULT

1. Aaron with 45 kg mass was inside the elevator. The elevator accelerates with 2 m/s2 upward. What will be Aaron’s weight reading in the ______________ as the elevator accelerates upward?Answer: 531 NThe weight of Aaron before the acceleration is 441 N.Weight = mass X acceleration

= 45 kg X 9.8 m/s2

= 441 N downward

o The normal force exerted is 441 N upwardo When the elevator accelerates his weight is 90 N.

Weight = mass X acceleration = 45 kg X 2 m/s2

= 90 N upward

READING IN __________________:

Normal force before the acceleration + the weight during the acceleration

441 N + 90 N = 531 N

Your apparent weight is greater when the elevator moves upward.

2. There are 120 waves that travel in 30 seconds. The distance of the all the waves is 5 m and the distance between crest and trough is 1m. What is the frequency in Hertz of the wave?

Answer: = 4 H or 4 hertz

Frequency is the number of wave or cycle in 1 second.o f =number waves/time

= 120 / 30 s= 4/s= 4 H or 4 hertz

3. Potassium nitrate (KNO3) is an ionic compound. The atomic number of each element is K-19, N-7 and O- 8. How many total numbers of valence electrons are there in the substance?

Answer: 24

K has 1 VE, N has 5 and one O has 6 VE and there are 3 O, so 6 times 3.

Total no. of Valence electron = 1+ 5 + (8X3)

= 24 VE

4. Bodies of water are polluted with toxic wastes, untreated sewage, and fertilizer run-offs from farm lands. One class of dangerous chemicals present in water is PCB (polychlorinated biphenyl). The concentration of PBC in an organism’s tissue increases at higher trophic level. What do you call this process of building up of pollutants in organisms at higher trophic levels in a food chain?

Answer: Biological magnification