Matter and Energy Chapter 2 Chemistry 1 5.0

Energy and Change Energy is the capacity to do work. All physical and chemical changes require energy. Endothermic - describes a process in which heat is absorbed from the environment. Exothermic – describes a process in which heat is released into the environment.

Law of Conservation of Energy Energy is neither created, nor destroyed. It just changes forms.

Heat Heat is the energy transferred between objects that are at different temperatures. This heat is always transferred from the hotter object to the colder object. Types of Energy Potential energy – stored energy Kinetic energy – energy of motion

Heat Temperature is not the same as heat. Temperature is a measure of the average kinetic energy of the particles in an object. A temperature change is a result of a energy transfer. Temperature vs. Heat Animation

TEMPERATURE SCALES                                                                                     

Celsius and Kelvin Temps. K = °C + 273 °C = K - 273 Zero Point on Kelvin Scale – Absolute Zero 0 K and -273 °C All motion of particles stops! No kinetic energy.

Heat Transfer Transfer of heat may not affect temperature. During a phase change, the temperature will remain constant until all of the substance has changed state. The temperature will increase when a substance is a solid, liquid, or gas.

Phase Change Diagram

Kinetic Theory of Matter Gases posses the greatest amount of kinetic energy. Two factors that determine the state of matter of a substance: speed of particles and distance There are two factors contribute to the attraction between the particles.

Kinetic Theory of Matter Substances change phases when they overcome these attractions. The overall kinetic energy will not change until the entire substance has completely changed. Comparison of the three states of matter

Specific Heat The amount of heat necessary to raise 1g of a substance 1°C. This is the relationship between energy transferred as heat and the substances temperature change.

Common Specific Heats

The scientific method is a systematic approach to gather knowledge. Observation Question Hypothesis Experiment Conclusion All hypotheses must be able to be tested in order to be a true hypothesis.

Experiment Natural Law – Describes how nature behaves Theory – Explains why nature behaves the way it does A theory and a hypothesis are both explanations, but a theory is an explanation formed after much experimentation.

Variables in a Experiment Independent Variable - You control Dependent Variable – Variable factor – what is being tested Experimental Control – Factor that remains constant for comparison

D. Factors in an Experiment Independent: most regular variable – goes on the X-axis Dependent: what you are testing – goes on the Y-axis Experimental Control: part of the experiment that stays the same. Dependent variable “Y” axis Independent variable “X” axis

Uncertainty in Measurement Measurements are uncertain because: 1) Instruments are not free from error. 2) Measuring involves some estimation. Precision –when the instrument gives you about the same results under similar conditions. The smaller the increments of measurement an instrument has, the more precise it can be. Accuracy – when the experimental value is close to the actual value.

What is the goal for a game of darts? Hitting the Bulls Eye!

Label the following data as accurate, precise, neither, or both. 1) 200g, 1g, 40g Neither 2) 78g, 80g, 79g Precise 3) 16g, 14g, 17g Accurate and Precise

Significant Figures and Digits A prescribed decimal that determines the amount of rounding off to be done base on the precision of the experiment. ALWAYS ESTIMATE 1 DIGIT MORE THAN THE INSTRUMENT MEASURES. Significant digits include measured digits and the estimated digit.

VI. Significant Digits A. Significant Digits include measured digits and estimated digits. Use Atlantic-Pacific Rule – imagine a US map decimal point decimal point Pacific Atlantic resent bsent

1100 2 significant digits 4 significant digits 1100. 8 significant digits 11.010000 2 significant digits 0.025 5 significant digits 0.00035000 1,000,100 5 significant digits Decimal Absent Start counting with the 1st nonzero digit and count all the rest. Decimal Present Start counting with the 1st nonzero digit and count all the rest.

How to use a graduated cylinder Read the meniscus

How to use a graduated cylinder 36.4 mL 19.0 mL 6.25 mL

How to read a triple beam balance 28.570 g Ohaus Triple Beam Balance Tutorial Reading A Triple Beam Balance Tutorial

How to read a triple beam balance 109.076 g Ohaus Triple Beam Balance Tutorial Reading A Triple Beam Balance Tutorial

Significant Digits in Addition and Subtraction Add or subtract numbers Answer can only be as exact as the least exact number. (Look at the decimal place) Ex. 4.1 cm + 0.07cm 4.17 cm 4.2 cm

Significant Digits and Multiplication and Division Multiply and Divide the numbers. Round answer to the same number of significant digits as the number with the fewest significant digits. Ex. 7.079 cm / 0.535 cm 13.2317757 13.2

Scientific Notation 1) 2700 2.7 x 103 2) 8,000,000 8 x 106 3) 0.0035 1) 2700 2.7 x 103 2) 8,000,000 8 x 106 3) 0.0035 3.5 x 10-3 4) 0.010 1.0 x 10-2

1st Commandment of Chemistry: KNOW THY CALCULATOR! Find the “EE” key – it may be a 2nd function! If you have a graphing calculator look for the following keys: Find the (-) key.

Look at the calculator that is similar to yours… Find the “Exp” or “x10x” 1st Law of Chemistry: Know Thy Calculator! Look at the calculator that is similar to yours… Find the “(-)” or the “+/-” key.

Scientific Notation 1) Multiply 3.7 x 102 by 5.1 x 103 Answer: 19 x 105 2) Divide 2.3 x 10-3 by 4.6 x 10-6 Answer: 5.0 x 102

Scientific Notation Add 9.67x102 + 8.5x103 Answer: 9.5 x 103