CHAPTER 1 REGULAR HOMEWORK
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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
- Formation of a precipitate
- Basically anytime the chemical state or formation changes
- If bonds or broken or made
- If energy is released or absorbed
- Melting/Boiling point
- State change
- Basically anything dealing with the molecules chemical composition (I know thats quite vague but truly that the nitty gritty of it)
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.
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)
- 3800 is the final answer because 0.013 has 2 sig figs
In adding or subtracting, your answer is only as accurate as the least accurate place value. In this case, it is the tenths place.
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!
- (50.1 + 171.137) = 221.237 -24.0 = 197.237
- (13.49 -13.41) =0 .08
- 197.237 x 25.807 = 5090.09
- 5090.09 /0 .08 = 63,626
- Round off with 1 sig fig because of 0.08 making your final answer 60,000
Density is defined as the mass of an object over its volume (g/cm3).
- 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
- 47.9 mL of liquid = 47.9 cm3 of liquid (use the hint given)
- Use the density formula.
- 45.7 g / 47.9 cm3 = 0.95 g/cm3
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
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