Chapter 2: MATTER & CHANGE

Properties of Matter Physical Properties –Characteristics that can be observed or measured without changing the identity of the substance –Boiling point, Melting point, density, hardness, odor, etc.

Physical Change –A change in a substance that does NOT involve a change in its identity –Melting, freezing, evaporation, condensation, etc. Properties of Matter

Chemical Properties/Changes –A substances ability to undergo changes that transforms the original identity to a different substance –Oxidizing (rusting), neutralizing, combustion, etc. Properties of Matter

How Does it Happen? Energy is transferred into or out of the system Endothermic –Heat is absorbed by the system –Feels cold to our hands Exothermic –Heat is released by the system –Feels hot to our hands

Law of Conservation Of Energy

Law of Conservation of Energy Visual Concepts Chapter 2

Temperature & Temperature Scales

THE SCIENTIFIC METHOD

Scientific Method Visual Concepts Chapter 2

The Scientific Method Problem Research Hypothesis Experiment Data Analysis Conclusions

Problem Statement / Purpose Identify a question to be answered Usually based on something commonly observed Example: Why do wheels appear to move backwards when they are on the freeway?

Research Find out what’s already known Use books, magazines, internet, newspapers, people, etc.

Hypothesis Form an educated guess to the answer based on what you found out Example: Wheels appear to spin backwards because of an optical illusion.

Experiment Develop procedures/tests to examine your problem It should have: –Control: the parts of the experiment that will be kept the same each & every time –Variable: the one thing that will change every time –Procedures: Step-by-step instructions anyone can follow to conduct the experiment.

Data Create an organized table of information, numbers, facts collected from your experiment Example: Wheel Speed (mph) Person APerson BPerson CPerson D 20forward 30Forward Cannot tell

Analysis Organize your data into a picture/chart/graph, etc. Example:

Conclusions A statement about your hypothesis followed by evidence from your experiment. Example: After 55 mph, our eyes cannot distinguish movement at that rapid pace. At this speed, an optical illusion is created by our eyes to process the information.

IN SUMMARY…

Section 2-3 MEASUREMENTS & CALCULATIONS

Accuracy and Precision Section 3 Measurements and Calculations in Chemistry Chapter 2

Visual Concepts Accuracy and Precision Chapter 2

Accuracy vs. Precision Accuracy –How close the measurements are to the real answer Precision –How reproducible the measurements are

Accuracy vs. Precision This is accurate!

Accuracy vs. Precision This is precise, but NOT very accurate!

Accuracy vs. Precision This is neither accurate NOR precise!

Accuracy vs. Precision This is Accurate AND Precise! You want to be BOTH!

Which instrument is more accurate?

Significant Figures Measurements written with all the known digits plus one uncertain digit Rules: “If Dot, then Right…If not, then Left”. If there is a decimal point, start at the first nonzero # and count everything to the right. 2. If there is no decimal point, start at the last nonzero# and count everything to the left.

Example 1 If dot, then Right. If not, then Left There is a dot, so start at the first nonzero # you see and count everything to the right. 4 sig. figs.

Example 2 Example 2: 600 There is NO dot, so start at the nonzero # and count everything to the left. 1 sig. fig.

Example There is a decimal point so start at the first nonzero # and count everything to the right. 3 sig. figs.

Scientific Notation Numbers are written in the form of M x 10 n 1 ≤ M ˂ 10 n is a any whole number (-/+) Video

Example 1 Write nm in scientific notation. The decimal has to be moved 4 places & it’s a small # 1.2 x nm

Example 2 Write mL in scientific notation. The decimal has been moved 4 places & it’s a large # 6.5 x 10 4 mL

1.Which of the following determines the temperature of a substance? A.charge on ions B.color C.motion of particles D.total mass of material Standardized Test Preparation Understanding Concepts Chapter 2

1.Which of the following determines the temperature of a substance? A.charge on ions B.color C.motion of particles D.total mass of material Standardized Test Preparation Understanding Concepts Chapter 2

2.Which of these processes is an endothermic physical change? F.an explosion G.melting of butter H.condensation of a gas I.formation of a solid when two liquids are mixed Standardized Test Preparation Understanding Concepts Chapter 2

2.Which of these processes is an endothermic physical change? F.an explosion G.melting of butter H.condensation of a gas I.formation of a solid when two liquids are mixed Standardized Test Preparation Understanding Concepts Chapter 2

3.Which of the following definitely indicates an error in an experiment? A.hypothesis not supported B.results contradict a theory C.unexpected results D.violation of a scientific law Standardized Test Preparation Understanding Concepts Chapter 2

3.Which of the following definitely indicates an error in an experiment? A.hypothesis not supported B.results contradict a theory C.unexpected results D.violation of a scientific law Standardized Test Preparation Understanding Concepts Chapter 2

4.Every chemical change involves F.the formation of a different substance. G.the vaporization of a liquid. H.separation of states of matter. I.the release of energy. Standardized Test Preparation Understanding Concepts Chapter 2

4.Every chemical change involves F.the formation of a different substance. G.the vaporization of a liquid. H.separation of states of matter. I.the release of energy. Standardized Test Preparation Understanding Concepts Chapter 2