7 Learning Check Which of the following items contain chemicals? A. Fertilizers B. Vitamins C. Happiness D. Iron nails E. Paints
8 Solution Which of the following items contain chemicals? A. Fertilizers contain chemicals B. Vitamins contain chemicals C. Happiness does not contain chemicals D. Iron nails contain chemicals E. Paints contain chemicals
Substance Substance- chemical that consists of one type of matter and always has the same composition and properties 9
13 Everyday Scientific Thinking Observation:The sound from a CD in a CD player skips. Hypothesis 1:The CD player is faulty. Experiment 1: When I replace the CD with another one, the sound from this second CD is OK. Hypothesis 2:The original CD has a defect. Experiment 2:When I play the CD in another player, the sound still skips. Theory: My experimental results indicate the original CD has a defect.
Scientific method State the problem (like a question) Hypothesis (suggest an answer to a problem) (If _ind var___ then _dep var___) Plan experiment Gather data Interpret data (look for patterns or trends) Conclusion, plan future work Publish results
Experiment Way of testing a hypothesis Has an independent and a dependent variable Independent variable- you define it, causes a change in another Dependent variable- changes in response to the ind. Var. Control group - reference to find out if there were any changes in the experimental groups.It has all the same elements except the Ind. Var
Tránsito de San Pedro wants to establish if the installation of radars will affect the average velocity of cars driving through MoronesPrieto. establish the problem (Will radars affect the velocity of cars?) Present the hypothesis (If there are radars in specific locations then cars will decrease their speed) Design the experiment (install radars in locations and measure speed with and without radars) identify independent (radars in specific locations) dependent variable (speed of cars) state the control group. (locations without radars)
Carol is a soccer player. She told Mark that Adidas training shoes have a greater performance than Nike training shoes, in the soccer field. establish the problem Present the hypothesis Design the experiment identify dependent and independent variable state the control group.
18 Learning Check The step of scientific method indicated in each is 1) observation 2) hypothesis 3) experiment 4) theory A. A blender does not work when plugged in. B. The blender motor is broken. C. The plug has malfunctioned. D. The blender does not work when plugged into a different outlet. E. The blender needs repair.
19 Solution The step of scientific method indicated in each is 1) observation 2) hypothesis 3) experiment 4) theory A. (1) A blender does not work when plugged in. B. (2) The blender motor is broken. C. (2) The plug has malfunctioned. D. (3) The blender does not work when plugged into a different outlet. E. (4) The blender needs repair. Cw-Do from page 9 problems: 1.12-1.14
25 Units in the Metric System In the metric (SI) system, one unit is used for each type of measurement: Measurement Metric SI length meter (m) meter (m) volume liter (L) cubic meter (m3) mass gram (g) kilogram (kg) time second (s) second (s) temperature Celsius (C) Kelvin (K)
30 For each of the following, indicate whether the unit describes 1) length, 2) mass, or 3) volume. ____ A. A bag of onions has a mass of 2.6 kg. ____ B. A person is 2.0 m tall. ____ C. A medication contains 0.50 g aspirin. ____ D. A bottle contains 1.5 L of water. Learning Check
31 For each of the following, indicate whether the unit describes 1) length, 2) mass, or 3) volume. 2 A. A bag of onions has a mass of 2.6 kg. 1 B. A person is 2.0 m tall. 2 C. A medication contains 0.50 g aspirin. 3 D. A bottle contains 1.5 L of water. Solution
32 Learning Check Identify the measurement with an SI unit. A. John’s height is 1) 1.5 yd 2) 6 ft 3) 2.1 m B. The race was won in 1) 19.6 s 2) 14.2 min 3) 3.5 hr C. The mass of a lemon is 1) 12 oz 2) 0.145 kg 3) 0.6 lb D. The temperature is 1) 85C 2) 255 K 3) 45F
33 Solution Identify the measurement with an SI unit. A. John’s height is 3) 2.1 m B. The race was won in 1) 19.6 s C. The mass of a lemon is 2) 0.145 kg D. The temperature is 2) 255 K
34 STEP 1 State the given and needed units. STEP 2 Write a plan to convert the given unit to the needed unit. STEP 3 Write equalities/conversion factors that connect the units. STEP 4 Set up problem with factors to cancel units and calculate the answer. Unit 1 x Unit 2 = Unit 2 Unit 1 Given Conversion Needed unit factor unit Guide to Problem Solving (GPS)
Often, two or more conversion factors are required to obtain the unit needed for the answer.
Unit 1 Unit 2 Unit 3
Additional conversion factors can be placed in the setup to cancel each preceding unit
Given unit x factor 1 x factor 2 = needed unit Unit 1 x Unit 2 x Unit 3 = Unit 3 Unit 1 Unit 2 Using Two or More Factors
39 How many minutes are in 1.4 days? Given unit: 1.4 days Needed unit: min Plan: days hr min Equalties: 1 day = 24 hr 1 hr = 60 min Set up problem: 1.4 days x 24 hr x 60 min = 2.0 x 103 min 1 day 1 hr Example: Problem Solving
Be sure to check your unit cancellation in the setup.
The units in the conversion factors must cancel to give the correct unit for the answer.
What is wrong with the following setup?1.4 day x 1 day x 1 hr 24 hr 60 min Units = day2/min is Not the needed unit Units don’t cancel properly. Check the Unit Cancellation
More units Area m2 = m x m Volume m3 = m x m x m Density mass/volume g/mL or Kg/L 41
K = oC + 273 Ex 23 oC = _______ K 135 K = ________ oC 1L = 1 dm3 1 m3 =1000L Ex 27 m3 = ________ L 42
43 Osmium is a very dense metal. What is its density in g/cm3 if 50.0 g of osmium has a volume of 2.22 cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3 Learning Check
44 Given: mass = 50.0 g volume = 2.22 cm3 Plan: Write the density expression. D = mass volume Express mass in grams and volume in cm3mass = 50.0 g volume = 2.22 cm3 Set up problem using mass and volume. D = 50.0 g = 22.522522 g/cm3 2.22 cm3 = 22.5 g/cm3 Solution
54 Comparing Numbers in Standard and Scientific Notation Number in Standard Format Scientific Notation Diameter of the Earth 12 800 000 m 1.28 x 107 m Mass of a human 68 kg 6.8 x 101 kg Mass of a hummingbird 0.002 kg 2 x 10-3 kg Length of a pox virus 0.000 000 3 cm 3 x 10-7 cm
55 Learning Check Select the correct scientific notation for each. A. 0.000 008 1) 8 x 106 2) 8 x 10-6 3) 0.8 x 10-5 B. 72 000 1) 7.2 x 104 2) 72 x 103 3) 7.2 x 10-4
56 Solution Select the correct scientific notation for each. A. 0.000 008 2) 8 x 10-6 B. 72 000 1) 7.2 x 104
57 Learning Check Write each as a standard number. A. 2.0 x 10-2 1) 200 2) 0.00203) 0.020 B. 1.8 x 105 1) 180 000 2) 0.000 0183) 18 000
58 Solution Write each as a standard number. A. 2.0 x 10-2 3) 0.020 B. 1.8 x 105 1) 180 000