PhySci Summative Test 2

Question 1

▪︎Crushing a can
▪︎Mixing sand with water
▪︎Dissolving sugar in water

Answer 1

Physical Change

Question 2

▪︎Baking a cake
▪︎Iron Rusting
▪︎Rotting Banana

Answer 2

Chemical Change

Question 3

▪︎no change in the fixed composition
▪︎only rearrangement of the molecules

Answer 3

Physical Change

Question 4

▪︎composition of a substance is changed into another substance.
▪︎involves change in color, odor, taste and release of gases.

Answer 4

Chemical Change

Question 5

Proper orientation / alignment of the reactant particles creates _____?

Answer 5

Effective bond formation

Question 6

Minimum amount of energy that the reactant particles must possess to initiate the reaction.

Answer 6

Activation Energy

Question 7

Reactions proceed at different rates. Some are slow, while others are fast. When a reaction occurs slowly, it is described to have a low rate of reaction. If a reaction occurs fast, it has a high rate of reaction.

Answer 7

True

Question 8

It states that, “For a chemical reaction to proceed, there should be an effective collision between the reactant particles.”

Answer 8

Collision Theory

Question 9

Two characteristics of collision to have chemical reaction:

Answer 9

1. Proper Orientation or alignment of reactants.
2. Enough energy to initiate a reaction.

Question 10

No proper orientation means…

Answer 10

no product formed.

Question 11

Lesser activation energy means…

Answer 11

faster rate of reaction.

Question 12

Temperature

Answer 12

▪︎Increase in temperature, increases the average speed of the particles.
▪︎At higher temperatures, more collisions can happen sufficient enough to surpass the activation energy of the reaction.
▪︎More collisions mean a higher possibility for successful reactions, resulting in a faster reaction.

Question 13

Relationship between Temperature and Rate of Reaction:

Answer 13

Direct Relationship

Question 14

Concentration

Answer 14

▪︎Increasing the concentration means increasing the amount of reacting species per unit volume. ▪︎This increases the probability of collision between the reactant particles because they are closer together.

Question 15

Relationship between Concentration and Rate of Chemical Reaction

Answer 15

Direct Relationship

Question 16

Surface Area

Answer 16

The greater the surface area, the greater frequency of collisions between reacting particles; hence, the faster the reaction.

Question 17

Relationship between Surface Area and Rate of Chemical Reaction:

Answer 17

Direct Relationship

Question 18

Substance that increases the rate of reaction by providing an alternative pathway for the reaction to occur- by lowering activation energy.

Answer 18

Catalyst

Question 19

A catalyst remains chemically unchanged at the end of the reaction.

Answer 19

True

Question 20

Which of the following statements is TRUE?

A. All reactions happen at the same rate.
B. Solid reactants can cause a faster reaction than the liquid ones.
C. Reaction proceed at different rates.
D. Catalysts are always needed for a reaction to proceed.

Answer 20

C. Reaction proceed at different rates.

Question 21

Which of the following statements is TRUE?

A. All reactions happen at the same rate.
B. Solid reactants can cause a faster reaction than the liquid ones.
C. Reaction proceed at different rates.
D. Catalysts are always needed for a reaction to proceed.

Question 22

Why do bakers prefer to use powdered sugar than blocked sugar?

A. it is more economic friendly
B. it is more convenient to use for it melts easily
C. it is sweeter than the other one
D. it is just the same

Answer 22

B. It is more convenient to use for it melts easily.

Question 23

A chemical reaction with a small activation energy will most likely

A. proceed at a fast rate
B. proceed at a slow rate
C. react at high temperature
D. react at a low pressure

Answer 23

A. Proceed at a fast rate.

Question 24

What happens to the particles if they are not properly oriented during the collision?

A. it will proceed anyway
B. The reaction will be delayed.
C. The reaction will need a catalyst.
D. no products are formed

Answer 24

D. No products are formed.

Question 24

The following are the ways we increase probability of collision for the reaction to proceed faster, EXCEPT:

A. lowering the volume of the reaction vessel
B. store the reaction in a fridge
C. use a stirring rod and mix the reaction
D. use smaller particles of the reactants

Answer 24

B. Store the reaction in a fridge

Question 25

Coal dusts burn faster than a single lump of coal.

Answer 25

Because coal dusts have more exposed surface area while combusting, so it burns faster than a lump of coal.

Question 26

Hydrogen and Oxygen react smoothly at room temperature in the presence of finely divided platinum.

Answer 26

The platinum serves as the catalyst in the reaction that’s why it proceeds smoothly.

Question 27

The rates of chemical reactions approximately double for each 10◦C rise in temperature.

Answer 27

For every 10◦C rise in temperature, makes the particles move faster hence, producing more collisions and faster rate of reactions.

Question 28

Milk sours if left out for a day or two but will last two weeks in the refrigerator.

Answer 28

Putting the milk in the refrigerator lowers the temperature of the decomposition
reaction.

Question 29

Wood burns explosively in pure O2, but slowly in air which is about 20% O2.

Answer 29

Since oxygen is requirement for a combustion reaction to occur, increasing its concentration yields to an explosive burn of wood.