Science exam

Question 1

What is buoyancy?

Answer 1

Buoyant force, or buoyancy, is the upward force of objects submerged in or floating in fluids. Buoyant force is the opposite of gravity force, pushing away from the center of the Earth.

Question 2

Why will an object float in a fluid?

Answer 2

Because its density is less than that of the fluid it is in (e.g. a boat and water)

Question 3

Fill in the blank: The principle of buoyancy was formulated by who?

Answer 3

Archimedes

Question 4

What is the formula to calculate density?

Answer 4

Density = Mass / Volume

Question 5

What is Density?

Answer 5

Density is the amount of matter in a certain unit volume of a substance. In other words, how closely packed together the particles are in a material.

Question 6

What is Archimedes’ Principle?

Answer 6

Archimedes’ Principle is the principle that is essentially “the amount of fluid displaced by an object is equal to the volume of that object”. Adding on, the buoyant force acting on the object equals the weight of the fluid displaced.

Question 7

Difference between weight and mass

Answer 7

Mass is a constant variable. It is the amount of matter in an object. Weight, on the other hand, can change because it is essentially created by the force of gravity acting on an object (e.g. how your weight is acting on a scale). The more weight someone has, the more gravity is acting on that person.

Question 8

What is the main principle behind hydraulics? What is Pascal’s Principle?

Answer 8

Hydraulics operates on Pascal’s principle, which states that pressure applied to a confined fluid is transmitted undiminished in all directions.

Question 9

List the details of one Water Brothers Episode.

Answer 9

I chose to research the “The Forever Chemicals” episode of The Water Brothers. The focus of the video is on Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS), a group of chemicals used to make products grease, water, and stain-resistant. The episode talks about the dangers of these chemicals, referring them as “forever chemicals” because they never degrade. Getting in the environment is dangerous because they don’t degrade. The episode also talks about PFAS in everyday products like food packaging and non-stick cookware, and their potential health and environmental risks. The Water Brothers talk about how PFAS can persist in the environment, contaminate water sources, and the health risks of the chemicals. One health risk that the brothers emphasize on is the increased risk of cancer, talking about how more firefighters die of cancer rather than dying in fires because of the PFAS exposure in the fire extinguishers they use.

Question 10

What is the buoyant force equal to?

Answer 10

Buoyant force is equal to the weight of the fluid displaced by the object.

Question 11

Define force.

Answer 11

The push or pull of an object. Whenever force is exerted on an object by another object, there is force acting on both objects (e.g. water and ice, buoyancy and gravity)

Question 12

What role does pressure play in hydraulics?

Answer 12

Pressure is used to create force and movement in hydraulic systems.

Question 13

Fill in the blank: The term __________ refers to the ratio of the mass of an object to its volume.

Answer 13

density

Question 14

Multiple choice: Which of the following is a common application of pneumatics? A) Hydraulic press B) Air brakes C) Water pumps

Answer 14

B) Air brakes

Question 15

What is the relationship between temperature and density for most substances?

Answer 15

As temperature increases, density generally decreases because the volume increases (if the substance isn’t in an enclosed space). When volume increases but mass doesn’t, the density decreases because D = M/V.

Question 16

True or False: Hydraulics can transmit more power than pneumatics.

Answer 16

True

Question 17

What is the standard unit of density in the SI system?

Answer 17

kilograms per cubic meter (kg/m³)

Question 18

Fill in the blank: The buoyant force is always directed __________.

Answer 18

upward

Question 19

Multiple choice: The density of water is approximately: A) 1000 kg/m³ B) 500 kg/m³ C) 1500 kg/m³

Answer 19

A) 1000 kg/m³

Question 20

What is the effect of increasing the size of an object on its buoyancy, assuming the density remains constant?

Answer 20

The buoyancy increases as size increases, provided the fluid density remains unchanged.

Question 21

What is a common use for hydraulic systems?

Answer 21

Heavy machinery operation, such as excavators and forklifts.

Question 22

Fill in the blank: The principle of buoyancy explains why ships can __________.

Answer 22

float

Question 23

Multiple choice: Which of the following factors does NOT affect buoyancy? A) Volume of the object B) Density of the fluid C) Temperature of the fluid

Answer 23

C) Temperature of the fluid

Question 24

First step of water treatment?

Answer 24

Step 1: Coagulation/flocculation. Increases the size of organic matter particles so that they can be removed more easily in the next step. Sulphuric acid is added to reduce the pH of the water (increase acidity). A coagulant, ferric sulphate is added so that particles in the water (e.g. natural organic matter) will be attracted to one another.

Question 25

Second step of water treatment?

Answer 25

Step 2: Dissolved air flotation: Removes the clumps of organic matter from the water and an air saturator takes water and supersaturates it with compressed air. The air bubbles float the clumps of organic matter to the top of the tank (much like how the raisins in the “dancing raisins” demo was, but the clumps don’t go back down because skimmers remove the clumps from the surface of the water.

Question 26

Third step of water treatment?

Answer 26

Step 3: Ozonation helps disinfect the water by using liquid oxygen to make ozone which improves the filter performance in the next treatment stage and destroys most harmful bacteria as well as improving the taste and odor of the water. Sodium bisulphite is added to the water to remove any leftover ozone.

Question 27

Fourth step of water treatment?

Answer 27

Step 4: Filtration, much like the name, filtrates remaining particles in the water, including parasites.

Question 28

Fifth step of water treatment?

Answer 28

Step 5: Chlorine disinfection kills bacteria and viruses, chlorine being one of the most efficient disinfectants of water known to science. In this stage, sodium hydroxide is added to raise the pH back to the original level so that the water becomes drinkable again.

Question 29

Sixth Step of water treatment?

Answer 29

Step 6: Ultraviolet light disinfection is used for a few seconds to penetrate any remaining waterborne microorganisms so that they can no longer cause infection and illness.

Question 30

heat capacity of water?

Answer 30

The heat capacity of something means the amount of heat it takes for something to change temperature. Water has an extremely high heat capacity, meaning that it takes a while for the temperature to change its state. It is also essentially why even a slight change in the temperature of the oceans is a huge amount of energy used and why climate change is dangerous. The reason water needs so much energy to change temperature is because some of the heat must be used to break the hydrogen bonds between the molecules. For reference, the amount of energy it takes to change the temperature of the oceans by one degree celsius is 5.5 trillion trillion Joules.

Question 31

Effect of salinity on density and heat capacity

Answer 31

Adding salt to water can change the heat capacity and density of the water. When the salt particles are added to the water, the substance becomes more packed together, increasing the density (how compact an object is). For example, dropping an egg in pure water makes the egg sink because its density is higher than that of water. Adding salt to the mixture, however, increases the density of the water to the point where the egg begins to float. Heat capacity is lowered and freezing point is lowered as well.