Chemical Building Blocks Chapter 1 1 Describing Matter

Chemical Building Blocks Chapter 1. 1 – Describing Matter

Key Terms l l l l Matter Chemistry Substance Physical Property Chemical Property Element Atom Chemical Bond l l l l Molecule Compound Chemical Formula Mixture Heterogeneous Mixture Homogeneous Mixture Solution

Matter l l Matter is anything that takes up space and has mass Most things we think of as “stuff” is matter l l l l Air Plastic Metal Wood Glass Paper Cloth People

Not matter? l With all of those things as matter, what isn’t matter? l l l Light Sound Emotions Electricity Force For now, we’re not going to focus on notmatter.

Properties of Matter l Matter can have many different properties. l l l Plastic has different properties than paper, or air. Can be hard, soft, rough, smooth, hot or cold, liquid, solid or gas. Some catch fire easily, while others won’t burn. Chemistry is the study of the properties of matter and how matter changes.

Substances l l l The properties of matter depends on its makeup. Some types of matter are called substances, while others are not. A substance will always have a particular makeup (called composition), and will always have a particular set of properties.

l l l Salt always has the same properties and composition, no matter where we find it. From seawater or a salt mine, all the same. On the other hand, think about a blueberry muffin. Some muffins are sweeter than others, some are more salty, or drier. Blueberry muffins are NOT a substance, because not always made up of the same composition. What goes into it can change amounts.

Every form of matter has two kind of properties, physical properties and chemical properties. l Physical Properties l l l l Something that can be observed without changing a substance into another substance. Freezing point Melting point Color Density Dissolves in water Used to identify substance l Metals l Chemical Properties l l Describes how the substance can change into another substance To be observed, must attempt to change it into another substance l l l Methane burns Iron rusts when exposed to oxygen Bread dough to produce gas from yeast

Elements l l Elements are the basic building block of matter An element is a pure substance that cannot be broken down into any other substance by chemical or physical means. Elements are the simplest substances Each element can be identified by its specific physical and chemical properties

l Familiar elements l l l Aluminum foil Inside of pennies is zinc Outside of pennies is copper Oxygen, and nitrogen gas in the air we breath Elements are often represented by a one- or two-letter symbol l Such as C for carbon, O for oxygen, N for nitrogen

l l l Since the most simple substances, what is the most basic form of an element? The atom is the basic particle from which all elements are made. Different elements have different properties, because their atoms are different. Atom comes from the Greek term meaning indivisible. We’ll learn more about atoms later.

When Atoms Attack! l l Well, not really. But they combine. When atoms combine, they form a chemical bond, which is a force of attraction between two atoms. In many cases, atoms combine to form larger particles called molecules, which are groups of two or more atoms held together by chemical bonds. Can be same elements or different elements

Compounds l l l All matter is made of elements, but most elements found in nature are combined with other elements. A compound is a substance made of two or more different elements chemically combined in a set ratio. This combination in a set ratio can be described by a chemical formula, which shows which elements are in the compound, and their ratio.

l Example: The gas we exhale is carbon dioxide. l l Represented by formula of CO 2 Shows one molecule of the compound of carbon dioxide contains 1 carbon for every 2 oxygen. Small number to right of symbol indicates number of atoms of the element. If ratio is different, you have a different compound. l H 2 O vs. H 2 O 2

l When elements combine to form a compound, the compound will have properties different from the elements it is made from. l l Sodium, chlorine and salt Carbon, hydrogen and oxygen to make sugar

Mixtures l l If not a substance, but still matter, is a mixture. A mixture is made of two or more substances (elements, compounds or both) that are together in the same place but NOT chemically combined. Each substance in a mixture keeps individual properties Parts of mixture not combined in a set ratio

l Two types of mixtures l Heterogeneous mixture l l l Can see different parts to it Soil, salad Homogeneous mixture l l l Parts evenly mixed so you can’t see different parts Salt water, kool-aid, air (clean) Solution is formed when substances are dissolved § § Sugar water Brass (copper and zinc)

Separating Mixtures l One of the other differences between mixtures and compound is you cannot PHYSICALLY separate a compound, but you can PHYSICALLY separate a mixture.

Chemical Building Blocks Chapter 1. 2 – Measuring Matter

Measuring Matter l l We use LOTS of different methods to measure the matter around us We commonly use l l l Weight and mass Volume Density

Vocabulary l l l Weight Mass International System of Units Volume Density

Weight and Mass l Weight l l How would you find your weight? Would it read the same if you were underwater? If you were on the moon? Weight is the measure of the force of gravity on you. l l Which is why it would be different on the moon, different force of gravity. On moon, 1/6 force of gravity, so only 1/6 your weight!

Chemical Building Blocks Chapter 1. 2 – Measuring Matter

Measuring Matter l l We use LOTS of different methods to measure the matter around us We commonly use l l l Weight and mass Volume Density

Vocabulary l l l Weight Mass International System of Units Volume Density

Weight and Mass l Weight l l How would you find your weight? Would it read the same if you were underwater? If you were on the moon? Weight is the measure of the force of gravity on you. l l Which is why it would be different on the moon, different force of gravity. On moon, 1/6 force of gravity, so only 1/6 your weight!

l Mass l l l Different from weight, but related. The force of gravity on you (weight) is based partially on your mass. Mass is the measurement of the amount of matter in the object. If you travel to the moon, does the amount of matter in you change? Would your mass change? Unlike weight, mass DOES NOT change with location, even when the force of gravity changes. The mass of an object is a physical property.

Units of mass l l l Almost everything in science has units, and we need to remember them. Mars Lander story. To unify units, scientists use a system called the International System of Units. l l Abbreviated SI, after its French name. SI unit of mass is the kilogram (kg) About 1 kg per 2 pounds. Can also use gram (g), which is 1/1000 of a kg.

Volume l l Volume is the amount of space that something takes up. Common units of volume include the liter (L), milliliter (m. L), and cubic centimeter (cm 3). l Interesting note: 1 m. L = 1 cm 3

Calculating Volume l l A bit of math! Oh noes! Finding volume for a rectangular object like a brick is easy. l l Volumerectangle = length x width x height Volume of an irregular object a little harder l Find its volume by process called displacement

Volume Displacement

Density l l Often confused with volume or surface area Similarly, just because two things have the same volume, not the same mass. l l Empty bucket vs. bucket filled with concrete Or, just because two things have the same mass, not the same volume l 1 kg of feathers takes up more space than 1 kg of sand.

l l l Density is an important property of matter (physical property) Density relates the mass of the object in a given volume. Often, expressed as number of grams in a given cubic centimeter. l l Water has density (at room temperature) of one gram per cubic centimeter (1 g/cm 3). This means that if I have one cubic centimeter of water, it would have a mass of 1 gram.

Volume w/ Math! l l Can be expressed mathematically as Example problem: A small block of wood floats on water. It has a mass of 200 g and a volume of 250 cm 3. What is the density of the wood?

Giving us an answer of:

Sink or Float? l l l Why do certain things sink and why do they float? Density! Take water for example: l l l Objects less dense than water will float Objects more dense than water will sink Why do helium balloons float?

Chemical Building Blocks Chapter 1. 3 – Changes in Matter

Section 3 Vocabulary l l l l Physical change Chemical change Law of conservation of mass Energy Temperature Thermal energy Endothermic change Exothermic change

Changes in Matter l l Chemistry is mostly the study of the changes in matter. Different ways matter can change Everything from building a sand-sculpture to receiving a sunburn can be a change in matter. There are different TYPES of changes in matter however.

Physical Changes l l l A physical change is any change that alters the form or appearance of matter but does not make any substance in the matter into a different substance. In other words, a substance that undergoes a physical change is still the same substance after the change. Examples?

Major Physical Changes of State l l l Changing from solid, liquid or gas. Water evaporating Ice melting Dry ice turning into gas Changes in Shape or Form l l Dissolving something Bending, crushing, breaking, chopping, etc.

Chemical Changes l l l A chemical change, or chemical reaction, is a change in matter that produces one or more new substances that weren’t there before. To simplify, creates new substances with different properties from the original substances. Examples?

Major Examples of Chemical Change l l l Combustion (burning) produces heat, light, and new substance Electrolysis breaks compounds into elements or simpler compounds Oxidation is when a substance combines with oxygen slowly (rusting is an example)

Conservation of Mass l l One of the basic laws of chemistry. If you measure carefully, the amount of mass (measure of amount of matter) does not change when a chemical change occurs. Meaning, no mass is gained or lost during a chemical reaction. Always same amount of mass. Mass just changes form.

Matter and Thermal Energy l l l We’ll talk more about this later in the year. Energy is the ability to cause change. Every chemical or physical change requires a change in energy. l l Bending a paper clip requires energy Ice melting absorbs energy from the surrounding matter Ice freezing releases energy into the surrounding matter. Candle wax burning releases energy.

Temperature and Thermal Energy l l Hot and cold are not useful, we use actual temperature. Temperature is the measure of the average energy of particles of matter. l l More energy = higher temperature Thermal Energy is the total energy of all the particles in an object. l Related to temperature, but not the same.

Thermal Energy and Changes in Matter l l l When matter changes, the most common form of energy released or absorbed is thermal energy. If energy is released by the change, is called an exothermic change. If energy is absorbed during the change, is called an endothermic change.

Chemical Building Blocks Chapter 1. 4 – Energy and Matter

Vocabulary l l l Kinetic energy Potential energy Chemical energy Electromagnetic energy Electrical energy

Forms of Energy l l Like matter, energy is never destroyed, it just changes form. When energy is transformed, it just changes from one form of energy into another.

Kinetic & Potential Energy l Kinetic energy is the energy of matter in motion. l l l Anything moving has kinetic energy How can something moving cause change? Potential Energy is the energy of an object due to its position. l l l Stretching a rubber band back increases its potential energy. Rolling a ball to the top of a hill increases its potential energy. How can this cause change?

Chemical Energy l l Chemical energy is a form of potential energy that is stored in the chemical bonds that holds atoms together. When a chemical change occurs, these bonds are broken, and new bonds form. l l l Sometimes this releases energy, sometimes it absorbs energy. This energy form is usually thermal energy. Gummy bear demonstration.

Electromagnetic Energy l l l A form of energy that travels through space as waves. Visible light is an example of this. Radio waves are examples of this.

Electrical Energy l l Electrical energy is the energy of electrically charged particles moving from one place to another. During many chemical changes, electrons move from one place to another.

Transforming Energy l l During a chemical change, chemical energy may be changed to other forms of energy. Other forms of energy may also be changed to chemical energy. Movement example.