Highlander Help

CHAPTER 1 REGULAR HOMEWORK

Resources:

Have you found videos, websites, or explanations that helped you understand this chapter? Let us know and we'll add them to "Resources" part of this page for other students to use.


              

 

Question 1

Which of the following processes describes a physical change?

Select one:
 Correct

 

Explanation

 A physical change in the simplest and most basic terms is any change that honest alter the substance after it occurs.

Examples:

  • State Changes (gas to liquid to solid)
    • Aka temperature and pressure changes
  • Density changes, which relate to the above because if you look at ice water, the ice floats on the water because it is less dense
  • Mass changes 



A chemical change is any change that does alter the substance after it occurs.

Examples:

  • Odor change
  • Rusting
  • Formation of a precipitate
  • Basically anytime the chemical state or formation changes
    • If bonds or broken or made
    • If energy is released or absorbed
 

Also no offense to whoever wrote this question, but proofreading is high key vital and the only staunch chemical changes are the meat cooking because the enzymes are denatured and when the food is metabolized because again enzymes are denatured by the gastric acid in the stomach changing the chemical composition making it easier to digest. But for the answer choices b,c, and d its really a guessing game, but cases can be made against b and d, so I guess c is technically the most correct as there truly is no question to a change in the wood's or nail's chemical composition, but regardless not a fan of this question.

 

Question 2

In the following description of Al, some of the properties are physical and some are chemical. Identify which of the properties are chemical?

Select one or more:
Correct
 Correct

 

Explanation

 Physical Properties

  • Colour
  • Density
  • Mass
  • Melting/Boiling point
  • State change
Chemical Properties

  • Basically anything dealing with the molecules chemical composition (I know thats quite vague but truly that the nitty gritty of it)

 

Question 3

A bug is observed to travel 15 cm in 2 seconds. What is the bug's speed in miles per hour?

Correct

 

Explanation

 Our fav is back dimensional analysis (ily af)


15 cm/ 2 sec *   1 in / 2.54 cm * 1 ft/ 12 in  * 1 mi/ 5280 ft * 3600 sec/ 1 hr

= 0.167 mi/hr

 

Question 4

What is 27.32 + 200 + 2? Pay attention to significant figures.

Hint is given in the feedback.

Correct

 

Explanation

In adding or subtracting, your answer is only as accurate as the least accurate place value. In this case, it is the place for the hundreds.



And were back what a throwback to like two days ago...

PEMDAS again kiddos

  • 27.32+ 200 = 227.32 (addition rule we deal with the least accurate number which in this case is 200, which has no decimal places)
  • 227.32 + 2 = 229.32
  • Round to the least accurate number (aka 200) which leaves you back again at 200 don't you love math, what a beautiful circle ya know...kumbaya and all that jazz.

 

Question 5

What is (9510 / 193.316 )/ 0.013? Pay attention to significant figures.

Hint is given in the feedback.

Correct

 

Explanation

In multiplying or dividing, your answer is only as accurate as the least number of significant figures. In this case, it is is the third number which has only two significant figures. 


PEMDAS ( and don't you ever forget ya hear)

(9510/193.316) =49.194

  • 49.194 (3 sig figs because 9510 has the least number of sig figs)
49.194/ 0.013=3784.15
  • 3800 is the final answer because 0.013 has 2 sig figs

 

Question 6

What is 2.30068 x 40.7 x 0.033301? Pay attention to significant figures. 

Hint is given in the feedback.

Correct

 

Explanation

In multiplying or dividing, your answer is only as accurate as the least number of significant figures. In this case, it is is 3 significant figures (the second number).


PEMDAS bb's

2.30068 x 40.7 = 93.6377 ( least sig figs is 40.7 with 3)

93.6377 x 0.033301 = 3.11822825

Final answer with correct sig figs (3) and rounding is 3.12

 

Question 7

What is 3.8841 -2.1? Pay attention to significant figures.

Hint is given in the feedback.

Correct

 

Explanation

In adding or subtracting, your answer is only as accurate as the least accurate place value. In this case, it is the tenths place. 


3.8841-2.1= 1.7841 ( least accuarate is 2.1 with a decimal place in the tenths so the answer is rounded to the correct tenths place)
Making the correct answer:  1.8

 

Question 8

What is (50.1 + 171.137 -24.0) x 25.807/(13.49 - 13.41)? Pay attention to significant figures. 

Hint is given in the feedback.
Correct

 

Explanation

 Do additions and subtractions first.


Please tell me you know what our first step...hint it starts with the same letter that  this sentence starts with.. wow I'm such a proud internet parent it is indeed PEMDAS.. you've really grown up and flourished kiddo I'm so proud of you!


  1. (50.1 + 171.137) = 221.237 -24.0 = 197.237
  2. (13.49 -13.41) =0 .08
  3. 197.237 x 25.807 = 5090.09
  4. 5090.09 /0 .08  = 63,626 
  5. Round off with 1 sig fig because of 0.08 making your final answer 60,000



 

Question 9

A 50.0 mL graduated cylinder has a mass of 50.9 g. When it is filled with an unknown liquid to the 47.9 mL mark, the cylinder and liquid combined have a mass of 96.6 g. Calculate the density of the liquid in g/cm3. (1 mL = 1 cm3.) 

Correct

 

Explanation

 Density is defined as the mass of an object over its volume (g/cm3).


  1. Isolate the mass of the liquid by subtracting the mass of the cylinder from total mass of the cylinder and liquid 
    • 96.6 g - 50.9 g = 45.7 g of liquid
  2. 47.9 mL of liquid = 47.9 cm3 of liquid (use the hint given)
  3. Use the density formula.
    • 45.7 g /  47.9 cm= 0.95 g/cm
 Fun Fact (of sorts): one easy way to memorize the density formula is to think of it is a broken heart... here look ( I know it's kinda cheesy but what can I say).
 

Question 10

Paper thickness varies. Typically, 100 sheets are about a cm thick. Atoms typically vary from 1 to 3 angstroms in radius. (An angstrom is 10-10 m.) Suppose a piece of paper is 0.0081 cm thick. How many atoms span the thickness if the radius of the atom is 1.94 angstroms? 

Correct


 

Explanation

Answer has 2 significant figures but remember to use 3 (because it is not requested).

FRIGGIN YEAH BOI @ DIMENSIONAL ANALYSIS

(ps I'm not about to write out angstroms every time so I am abbreviating that ish to angst just because it amuses me)


.0081 cm * 1 m / 100 cm * 1 angst / 10-10 m *  1 atomic radius/ 1.94 angstroms * 1 atom / 2 atomic radii = 208762.89 atoms



 

Question 11

The distance between the centers of two atoms in a diatomic molecule is 1.28 angstroms. (An angstrom is 10-10 m.) Calculate the distance in feet. 

Correct

 

Explanation

1.28 angst * 10-10 m/ 1 angst * 100 cm/1 m * 1 in /2.54  cm * 1 ft/12 in = 4.2 * 10-10 ft


Its dimensional analysis..once again..what a shock..oh my heart...et brutus.

 

Question 12

What is the area in square meters of 497 g Al foil that has a thickness of 18252 nm? The density of Al is 2.70 g/cm3.

Correct

 

Explanation

 Work backwards my children.


Start with the density to extrapolate the volume

  • 497 g/ 2.70 g/cm3  =  184.07 cm3 
Using the volume now divide using similar units by the thickness to attain the area as volume is composed of area multiplied by a third dimension in this case the thickness.
  • 18252 nm * cm / 1e7 nm = .0018252 cm
  • 184.07 cm3  / .0018252 cm =  100849.22 cm^2 (remember we need it in square meters)
  • 100849.22 cm^2  *  1 m^2/ (100 cm)^2 = 10.08 m^2
 

Question 13

Gold has a density of 19.3 g/cm3. Do you think you could carry 2.00 cubic ft (rhetorical--don't answer)? How many pounds does 2.00 cubic feet of gold weigh? [453.6 g = 1 lb, 2.54 cm = 1 in, and 1 ft = 12 in.] 

Correct

 

Explanation

 BRUH... no matter how jacked or swole you think you are don't attempt this at home.


2 ft^3 * (12 in)^3/ 1 ft^3 * (2.54 cm)^3/ 1 in^3 * 19.3 g/cm^3 * 1 lb/ 453.6 g = 2409.7 [as long as you're answer is within similar sig fig parameters moodle will let you slide]

 

Question 14

A certain liquid boils at 59 oC. What is the temperature in degrees Fahrenheit? 

Correct

 

Explanation

Yes, unfortunately in this beautiful and blessed nation of ours we are still tainted by the customary system, but I'm here to save you the headache and trouble and show you how to convert from this system to our good reliable metric system.


F = 1.8 * C +32

F = 1.8 * (59) + 32

F=138.2

 

Question 15

A certain liquid boils at 53 oC. What is the temperature in Kelvin?
 
Correct

 

Explanation

 Honestly Kelvin is super dope so I'm not going to hate on it even though its the third temperature scale we have to deal with.


K = C + 273.15 (yes this wasn't a mistake this is the initial eqn.)

K= 53 + 273.15 

K = 326.15

 

Question 16

A certain compound freezes at 153 K. What is the temperature in degrees Fahrenheit? 

Correct

 

Explanation

C=K-273.15

C= 153 - 273.15

C= -120.15

F= 1.8 * C +32

F= 1.8 * (-120.15) + 32

F = -184.27

 

Question 17

A scientific oven is programmed to change temperature from 88.3 ºF to 230.6 ºF in 1.50 minute(s). Express the rate of change in degrees Celsius per second. 

Correct

 

Explanation

 Remember these two don't increment in the same fashion so you can't find the rate in Fahrenheit and then convert, so to keep things simple look below.


  • 1.5 min * 60 sec / 1 min = 90 sec

You need to convert from the initial and final temperatures in Fahrenheit to Celsius because their aren't the same number of degrees in between both (take for example 230.6-88.3  =142.3 F degrees while 110.3 -31.28 =79.02 C)

  • 230.6 F = 110.3 C
  • 88.3 F =31.28 C
  • 79.02 C / 90 s = .87 C/ s




 

Question 18

The volume of a liquid is 65.3 ±0.3 cm3. Its mass is 49.5 ±0.5 g. What is the maximum density of the liquid in g/cm3

Correct

 

Explanation

 Maximum density will occur from a high numerator and a low denominator.


So in terms of density a high mass and a low volume, so we will take those respective values and divide them to get the max density.


(49.5+.5)g / (65.3-.3cm3)

50 g / 65 cm3


= .76923 g/cm3

 

Question 19

What is the minimum density of the liquid in g/cm3?

Correct

 

Explanation

 The minimum density will be the exact opposite with the lowest mass in the range and the highest volume in the range.


(49.5-.5)g / (65.3+.3cm3)

49 g / 65.6 cm3

= .7469  g/cm3


 

Question 20

What is the average density of the liquid in g/cm3? Hint, it is the average of the maximum and the minimum possible densities of the liquid. Note, you can get the right answer for this problem with the wrong min. and max. densities because of offsetting errors.

Correct

 

Explanation

 Take the maximum and minimum density and divide it by two.

(0.76923 + 0.7469) / 2 = .758

 

Question 21

What is the range in density of the liquid? The density = average densigy ± range. (Hint, range = the difference of the maximum and the minimum density of the liquid divided by 2.)

Correct

 

Explanation

Answer should be report to 3 decimal places since density is reported to 3 decimal places.


Subtract the minimum from the maximum and divide the answer by 2 in order to get a +/- range. 


0.76923 - 0.7469 = .02233 / 2 = +/-  .011