sci 7 q1 7 make accurate measurements using standard units for physical quantities and organize.ppt

accurate measurements grade 7

1. MeasurementMeasurement
Cartoon courtesy of NearingZero.net

2. Learning Competency:
•Make accurate measurements using
standard units for physical quantities and
organize the collected data when carrying
out a scientific investigation

3. Measurement of Length
3

4. Metric Units of Length
Exponential
Unit AbbreviationMetric Equivalent Equivalent
kilometerkm 1,000 m 10
3
m
meter m 1 m 10
0
m
decimeterdm 0.1 m 10
-1
m
centimetercm 0.01 m 10
-2
m
millimetermm 0.001 m 10
-3
m
micrometerm 0.000001 m 10
-6
m
nanometernm 0.000000001 m 10
-9
m
angstrom Å 0.0000000001 m 10
-10
m
3

5. How many millimeters are there in 2.5
meters?
It must cancel
meters.
It must introduce
millimeters
5
unit
1 x conversion factor = unit
2
m x conversion factor = mm
The conversion factor must
accomplish two things:

6. The conversion factor takes a fractional
form.
6
mm
m x = mm
m

7. Convert 2.5 meters to millimeters.
Use the conversion factor with millimeters in
the numerator and meters in the denominator.
7
1000 mm
x
1 m
2.5 m = 2500 mm
3
2.5 x 10 mm

8. 8
Convert 16.0 inches to centimeters.

9. Convert 16.0 inches to
centimeters.
9
16.0 in
2.54 cm
x
1 in
= 40.6 cm
2.54 cm
1 in

10. Convert 3.7 x 10
3
cm to micrometers.
10
3
3.7 x 10 cm
1 m
x
100 cm
6
10 μm
x
1 m
7
= 3.7 x 10 μm
Centimeters can be converted to
micrometers by writing down conversion
factors in succession.
cm  m 
meters

11. Convert 3.7 x 10
3
cm to micrometers.
11
Centimeters can be converted to
micrometers by two stepwise conversions.
cm  m  meters
3
3.7 x 10 cm
1 m
x
100 cm
1
= 3.7 x 10 m
6
10 μm
x
1 m
7
= 3.7 x 10 μm
1
3.7 x 10 m

12. Measurement of Mass
12

13. Metric Units of mass
13
Exponential
Unit AbbreviationGram Equivalent Equivalent
kilogram kg 1,000 g 10
3
g
gram g 1 g 10
0
g
decigram dg 0.1 g 10
-1
g
centigramcg 0.01 g 10
-2
g
milligrammg 0.001 g 10
-3
g
microgramg 0.000001 g 10
-6
g

14. Convert 45 decigrams to grams.
14
45 dg
1 g
x
10 dg
= 4.5 g
1 g = 10 dg

15. Example 2: An atom of hydrogen weighs 1.674 x
10
-24
g. How many ounces does the atom weigh?
1 lb
x
454 g
-24
1.674 x 10 g
-27
3.69 x 10 lb
16 oz
x
1 lb
-26
5.90 x 10 oz
-27
3.69 x 10 lb
1 lb = 454 g
16 oz = 1 lb
Grams can be converted to ounces by a series
of stepwise conversions.
14

16. Example 2: An atom of hydrogen weighs 1.674
x 10
-24
g. How many ounces does the atom
weigh?
16
-24
1.674 x 10 g
1 lb
x
454 g
16 oz
x
1 lb
-26
5.90 x 10 oz
Grams can be converted to ounces using
a linear expression by writing down
conversion factors in succession.

17. Measurement of Volume
17

18. •In the SI system the standard unit of
volume is the cubic meter (m
3
).
•The liter (L) and milliliter (mL) are the
standard units of volume used in most
chemical laboratories.
18
•Volume is the amount of space
occupied by matter.

19. 19

20. Convert 4.61 x 10
2
microliters to milliliters.
20
Microliters can be converted to milliliters by a series
of stepwise conversions.
L  L  mL
6
1 L
x
10 μL
2
4.61x10 μL
-4
4.61x10 L
-1
= 4.61 x 10 mL
-4
4.61x10 L
1000 mL
x
1 L

21. Convert 4.61 x 10
2
microliters to milliliters.
21
Microliters can be converted to milliliters using a
linear expression by writing down conversion
factors in succession.
L  L  mL
2
4.61x10 μL
6
1 L
x
10 μL
1000 mL
x
1 L
-1
= 4.61 x 10 mL

22. Measurement of
Temperature
22

23. Heat
•A form of energy that is associated with the
motion of small particles of matter.
•Heat refers to the quantity of this energy
associated with the system.
•System is the entity that is being heated or
cooled.

24. Temperature
•A measure of the intensity of heat.
•It does not depend on the size of the
system.
•Heat always flows from a region of higher
temperature to a region of colder
temperature.
24

25. Temperature Measurement
•The SI unit of temperature is the Kelvin.
•There are three temperature scales: Kelvin,
Celsius and Fahrenheit.
•In the laboratory temperature is commonly
measured with a thermometer.
25

26. Degree Symbols
26
degrees Celsius =
o
C
Kelvin (absolute) = K
degrees Fahrenheit =
o
F

27. To convert between the scales use the
following relationships.
27
o o o
F - 32 = 1.8 x C
o o o
F = 1.8 x C + 32
o
K = C + 273.15

o
o F - 32
C =
1.8

28. 28

180 Farenheit Degrees
= 100 Celcius degrees
180
=1.8
100

29. It is not uncommon for temperatures in the
Canadian planes to reach –60
o
F and below during
the winter. What is this temperature in
o
C and K?
29

o
o F - 32
C =
1.8
o o60. - 32
C = = -51C
1.8

30. It is not uncommon for temperatures in the
Canadian planes to reach –60
o
F and below
during the winter. What is this temperature in
o
C and K?
30
o
K = C + 273.15
o
K = -51C + 273.15 = 222 K

31. Density
31

32. 32
Density is the ratio of
the mass of a
substance to the
volume occupied by
that substance.
mass
d =
volume

33. 33
The density of
gases is expressed
in grams per liter.
g
d =
L

34. 34
Density varies with temperature
o
2
4C
H O
1.0000 g g
d = = 1.0000
1.0000 mL mL
o
2
80C
H O
1.0000 g g
d = = 0.97182
1.0290 mL mL

35. 35

36. 36

37. Examples
37

38. A 13.5 mL sample of an unknown liquid has a
mass of 12.4 g. What is the density of the liquid?
38
M
D
V
 0.919g/mL
12.4g
13.5mL


39. A graduated cylinder is filled to the 35.0 mL mark with water.
A copper nugget weighing 98.1 grams is immersed into the
cylinder and the water level rises to the 46.0 mL. What is the
volume of the copper nugget? What is the density of
copper?
g/mL8.92
mL11.0
g98.1
V
M
D 
39
46.0 mL
98.1 g
35.0 mL
coppernugget final initial
V =V -V = 46.0mL - 35.0mL = 11.0mL

40. The density of ether is 0.714 g/mL. What is the
mass of 25.0 milliliters of ether?
Method 1
(a) Solve the density equation for mass.
40
mass
d =
volume
(b) Substitute the data and calculate.
mass = density x volume
0.714 g
25.0 mL x = 17.9 g
mL

41. The density of ether is 0.714 g/mL. What is the
mass of 25.0 milliliters of ether?
Method 2 Dimensional Analysis. Use density as a
conversion factor. Convert:
41
0.714 g
25.0 ml x = 17.9 g
mL
mL → g
g
mL x = g
mL
The conversion of units is