1. Ch. 2 section 1-2 answers

2. What are base units?
They are defined units in a system of measurements.
A base unit is independent of other units.

3. Provide the seven base units of SI.
Seconds for time
Meters for length
Kilogram for mass
Kelvin for Temperature
Mole for Amount of substance
Ampere for electric current
Candela for luminous intensity

4. What are derived units? They are measurements that combines base units
Volume - cm3
Speed- m/s
Density- g/cm3

5. Define density
Density is the ratio that compares the mass of an object to its volume. Density- g/cm3

6. Displacement of water from 20 to 40 gives us the volume of 20 mls.
1. A piece of matter with a mass of 147 g is placed in a 50 mL graduated cylinder. The water level rises from 20mL to 40 mL. What is the density of the metal?
Displacement of water from 20 to 40 gives us the volume of 20 mls.
Density = mass/volume
147g / 20ml = 7.35 g/ml

7. So we are missing the volume D=m/x 4g = 20g 1ml Xml
2. What is the volume of a sample that has a mass of 20 g and a density of 4g/mL?
So we are missing the volume D=m/x
4g = 20g
1ml Xml
Cross multiply and divide
4g xml = 20g/ml =
4g g
5 ml

8. Aluminum’s density is 2.7 g/ml 20g = 4 g/cm3 5 cm3
3. A metal cube has a mass of 20 g and a volume of 5cm3. Is the cube made of pure aluminum? Explain you answer. See practice problem help.
Aluminum’s density is 2.7 g/ml
20g = 4 g/cm3
5 cm3
No, this is not pure aluminum

9. What is the Kelvin scale, where does chemistry use this measurement?
It’s the SI base unit of temperature where 273K is the freezing point of water and the boiling point of water is 373K
Kelvin is used in describing the behavior of gases.

10. Convert the following 450 °C to ___________K
Convert the following °C to ___________K 25K___________°C 3°C to _____________K 600K___________°C 0°C to _____________K 0K___________°C -60°C to___________K 375K___________°C *Celsius to Kelvin add 273 *Kelvin to Celsius subtract 273
723
-248
276
327
273
-273
213
102

11. What is scientific notation?
Scientific notation expresses numbers as multiple of two factors:
A number between 1 and 10
And ten raise to a power, exponent
The exponent tells you how many times the first factor must be multiplied by ten.
When numbers larger than 1
Power of 10 is in the positive
When numbers smaller than 1
Power of 10 is in the negative

12. What is scientific notation?
700m
38000m m m
0.0054kg kg
g kg
h kg
7x 102 m
3.8 x 104 m
4.5 x 106 m
6.85 x 1011 m
5.4 x 10-3 kg
6.87 x 10-6 kg
7.6 x 10-8 kg
8 x kg

13. What is the rule when adding or subtracting exponents?
When adding or subtracting numbers written in scientific notation, you must be sure that the exponents are the same before doing the arithmetic.

14. 14. Read instructions and solve. a
14. Read instructions and solve. a. 5 X 10-5m + 2 X 10-5m = _____________________ b 7 X108m – 4X108m = _______________________ e X 104 kg X103kg __________________ g X 105kg – 2.8 X 104kg ___________________
7 x 10-5 m
3 x 108 m
15.1 x 103 kg
Change exponents to be the same
1.51 x 104 kg
12.6 x 103 kg
4.11 x 105 kg
Change exponents to be the same
0.28 kg x 105 kg

15. What is the rule when multiplying or dividing exponents?
For multiplication, you multiply the first factors. Then, you add the exponents.
For division, you divide the first factors. Then, you subtract the exponent of the divisor from the exponent of the dividend.

16. 15. Read instructions and solve. a. 4 X 102cm x 1 X 108cm = c
15. Read instructions and solve. a. 4 X 102cm x 1 X 108cm = c. 3 X101 cm x 3 X10-2cm = 16b. 8 X 104 g ÷ 4 X101 cm3 = d. 4 X 10-3g ÷ 2 X 10-2 cm3 =
4 x 1010 cm2
9 x 10-1 cm2
2 x 103 g/cm
2 x 10-1 g/cm

17. What is a conversion factor?
A conversion factor is a ratio of equivalent values used to express the same quantity in different units.
A conversion factor is always equal to 1.

18. 19. How many seconds are there in 24 hours?
Place the units you want to get rid of across from each other
Place starting amount here
24 hours
60 minutes
60 seconds
= 86,400 sec
8.64 x 104 sec
1 hour
1 minutes
Place
conversion factor
here
Place
conversion factor
here

19. Place starting amount here
20. A car is traveling 90.0 kilometers per hour. What is its speed in miles per minute? One kilometer = 0.62 miles.
Place the units you want to get rid of across from each other
Place starting amount here
90 km
0.62 miles
1 hour
= 0.93 miles/min
9.3 x 10-1 miles/min
1 hour
1 km
60 minutes
Place
conversion factor
here
Place
conversion factor
here

20. The Metric System
Base Units
Length
meter
Mass
gram
Time
seconds

21. kilo 1000 hecta 100 deca 10 Base 1 deci 0.1 centi 0.01 milli 0.001
Prefix
kilo
1000
hecta
100
deca 10
Base 1
deci
0.1
centi
0.01
milli
0.001

22. Put in the prefix Prefix + base = measurement kilo- meter 1000 meters
centi-
liter
0.01 liters
deca-
gram
10 grams

23. 0.03 hm 3 Conversions kilo hecta deca Base deci centi milli
300. centimeters = hm
Move the decimal point toward the prefix you want.
0.03 hm
The decimal moved to the left 4 times 3

24. 25 kilograms to _______________ decigrams
Practice
kilo
hecta
deca
Base
deci
centi
milli
250000
25 kilograms to _______________ decigrams
Where do we start?
Kilo
Where do we end?
deci
How many spots and which direction?
4 to the right

25. 0.0043 grams to _______________ hectagrams 0.000043
Practice
kilo
hecta
deca
Base
deci
centi
milli
grams to _______________ hectagrams
38.508
38508 meters to _______________ kilometers
1.34 milliliters to _______________ liters
0.9756
975.6 liters to _______________ kiloliters

26. Scientific Notation Used to express really big or small numbers
Really big- power of 10 is in the positive
Really small- power of 10 is in the negative
You move the decimal point behind the first NON ZERO number.

27. Practice 1392000 km Is this a big number or small?
Is my power of 10 in the positive or negative?
Where does the decimal go?
1.392 x 106 km

28. Practice Scientific Notation
grams
3.457 x 10-6 grams
48000 meters
4.8 x 104 meters
meters
2.563 x 10-4 meters
meters
9.67 x 10-9 meters
8,900,000,000,000 kilometers
8.9 x 1012 km

29. Adding & Subtracting Scientific Notation
Make sure that the exponents are the same!
1.3 x 10-2 kg x 10-2 kg =
3.487 x 104 kg x 105 kg =
Change them to match (doesn’t matter which)
x105kg x 105 kg =
3.8 x 10-2 kg
x 105kg (is this correct??)
4.134 x 105kg (is this correct??)

30. Practice
7 x 10-5 m
5 x 10-5 m + 2 x 10-5 m =
1.26 x 104 kg x 103 kg =
1.5 x 104 kg
9 x 102 m -- 7 x 102 m =
2 x 102 m
5.36 x 10-1 km – 7.40 x 10-2 km =
4.62 x 10-1 km

31. Multiplying Scientific Notation
Multiply the factors first!!
Then add the exponents
Take care in assigning the sign to the exponent
Adding +3 to +4 = 7 but +3 to -4 = -1
Subtracting -6 from -4 = 2 but -4 from -6 = -2
(2 x 103 kg) X (3 x 102 kg) =
Rule 1 = 6 Rule 2 =105
6 x 105 kg2

32. Practice Multiplying Scientific Notation
(4 x 102 cm) (1 x 108 cm) =
4 x 1010 cm2
(3 x 101 cm) (3 x 10-2 cm) =
9 x 10-1 cm2
(1 x 103 cm) (5 x 10-1 cm) =
5 x 102 cm2

33. Dividing Scientific Notation
Divide the factors first!!
Then subtract the exponent of the divisor from exponent of the dividend
(9 x 108 kg) ÷ (3 x 10-4 kg) =
Rule 1: 9 ÷ 3 = 3
Rule 2: = 12
3 x 1012 kg

34. Practice Dividing Scientific Notation
(6 x 102 g) ÷ (2 x 101 g) =
3 x 101 g
(9 x 105 cm) (3 x 10-1 cm) =
3 x 106 cm
(4 x 10-3 cm) (2 x 10-2 cm) =
2 x 10-1 cm