# Chap 1 Section 2- Describing Matter

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Chap 1 Section 2- Describing Matter
Characteristics of matter The SI system – units of measurement Conversion of the units and calculation Identify physical and chemical properties.

Matter Cloud Gravity Apple Student Electron Carbon dioxide Heat Fire
Air Trees Atom Gravity Student Carbon dioxide Fire Molecule Dream Drop of water

Matter All matter have physical properties.
Matter has Volume, Mass and Density. Volume – the space the object occupies. Mass – the quantity of matter. Density – the ratio of mass to volume How to measure and calculate? What is the units of these physical properties

Systems of Units SI System: The international system of units established by the International Committee on Weights and Measures. Such units are based on strict definitions and are the only official units for physical quantities. US Customary Units (USCU): Older units still in common use by the United States, but definitions must be based on SI units.

SI (System International Unit )
Chapter 1 SI (System International Unit )

Seven Fundamental Units

Units for Chemistry Quantity SI unit USCS unit Mass kilogram (kg)
In Chemistry we use only a few fundamental quantities: mass, volume, and mole etc. An additional quantity, density is derived from some of above units. Quantity SI unit USCS unit Mass kilogram (kg) slug (slug) Volume Cubic meter ( ) Cubic foot Temperature Celsius ( ) Fahrenheit (F) Amount of substance Mole

SI system When working with numbers, be careful to distinguish between a quantity and its unit. Quantity describes something that has magnitude, size, or amount. Unit is a quantity adopted as a standard of measurement.

Base units can be too large or too small for some measurements, so the base units may be modified by attaching prefixes.

Procedure for Converting Units
Write down quantity to be converted. Define each unit in terms of desired unit. For each definition, form two conversion factors, one being the reciprocal of the other. Multiply the quantity to be converted by those factors that will cancel all but the desired units.

Example 1: Convert 12 in. to centimeters given that 1 in. = 2.54 cm.
Step 1: Write down quantity to be converted. 12 in. Step 2. Define each unit in terms of desired unit. 1 in. = 2.54 cm Step 3. For each definition, form two conversion factors, one being the reciprocal of the other.

Example 1 (Cont. ): Convert 12 in. to centimeters given that 1 in. = 2
Example 1 (Cont.): Convert 12 in. to centimeters given that 1 in. = 2.54 cm. From Step or Step 4. Multiply by those factors that will cancel all but the desired units. Treat unit symbols algebraically. Wrong Choice! Correct Answer!

Practice problems Let’s do some example problem together
Convert 2.53 mL to Liters Convert 1258 cm to meters Convert 15 g to kilograms Page 14 # 1-3 work with your partner who is sitting next to you.

Properties of Matter Physical Properties
A physical property of a substance is a characteristic that does not involve a chemical change. Physical properties of a substance can be determined without changing the nature of a substance.

Properties of matter Physical properties
Physical properties describe a matter. One of properties is Density.

Concept Map of Density Mass Volume Units for volume of a regular solid
the amount of matter something has Balance or scale Water displacement graduated cylinder Gram ml ml Units for volume of an irregular object the amount of space something takes up Units for volume of a liquid Of an irregular object is measured by L x W x H Units for mass

Properties of Matter, continued
The density of a substance is the same no mater what the size of the sample is.

Example Find the density of sulfuric acid if 15 cm3 has a mass of 27.6 g. Unknown density of sulfuric acid data V = 15 cm3 M = 27.6 g D = M/V 27.6g / 15 cm3 = 1.84 g/cm3

Practice problems Find the density of a block of metal which is 16 mm long, 12 mm wide and 5 cm high. The mass of this block is mg. Find the mass in grams of a bar of silver 6 cm long, 10 cm wide and 4 cm high. Silver has a density of 10.5 g/cm3 Find the volume of a container necessary to hold 200 g of mercury. The density of mercury is g/cm3.

Properties of Matter, continued Chemical Properties
A chemical property a property of matter that describes a substance’s ability to participate in chemical reactions. A chemical property of many substances is that they react with oxygen. example: rusting Some substances break down into new substances when heated.