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Brawley Middle Sixth Grade Science Matter: properties and change Christophe Fatton

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Objectives 1 Recognize that all matter is made up of atoms. Recognize that atoms of the same element are similar, but different from atoms of other elements

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Definition of Matter anything that has mass and takes up space Water in a bucket

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Key concepts Key Concepts Chemistry is the study of matter. Matter is made up of extremely tiny particles called atoms and molecules. Atoms and molecules make up the three common states of matter on Earthsolids, liquids, and gases. The particles of a liquid are attracted to one another, are in motion, and are able to move past one another. Being a solid, liquid, or gas is a property of a substance.

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Atoms and molecules Atoms are the tiny particles that are considered to be the basic building blocks of all matter. The nucleus is made of protons and neutrons. The shell has the electrons. The protons and electrons are positively or negatively charged. Molecules are made of two or more atoms that are connected or bonded together.

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MatterSolid, Liquid, Gas On Earth, matter is either found as a solid, liquid, or gas.

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MatterSolid, Liquid, Gas particles (atoms or molecules) that make up the solid, liquid, and gas are moving Matter (solid, liquid, and gas) is made up of tiny particles called atoms and molecules. The atoms or molecules that make up matter are always in motion. These first two ideas make up a very important theory called the Kinetic-molecular theory of matter. Basically the state of a sample of matter depends on TEMPERATURE!

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MatterSolid, Liquid, Gas Atoms or molecules that make up solid, liquid or gas are attracted to one another

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Properties of Matter Matter has both physical and chemical properties. It can also be classified according to these physical and chemical properties.

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Matters Physical Properties Physical properties: can be observed without changing the make-up, or identity, of matter.

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Examples of Physical Properties

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Physical properties cont..

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Matters Chemical Properties Chemical Property: ability to change new matter with different properties. Chemical Property: new substance has chemical and physical properties different from the original substance. Chemical reaction: When one or more substances change to form one or more new substances.

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Chemical Property

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Example of Chemical Properties Chemical Property What It MeansWhat Students Should Understand Reactivity with oxygen Ability of a substance to react with oxygen A reaction with oxygen results in processes such as rusting and tarnishing of some metals. Non-reactivity with oxygen Ability of a substance to resist reacting with oxygen Not all substances react with oxygen. This knowledge is used in the real world to prevent rusting and tarnishing. For example, a metal that is reactive with oxygen can be coated or galvanized with a non-reactive substance to prevent rusting or tarnishing. Flammability Ability of a substance to burn Everything will burn, given a high enough temperature. When a substance burns, ash and smoke may not be given off. Fumes, which may be toxic, can be a product of the reaction. Non-flammability Ability of a substance to resist burning This property is useful in the real world when selecting certain substances that must withstand extreme heat.

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Physical and Chemical Changes Physical change: only the physical properties of matter, but not the chemical properties. Burning paper into ash Chemical change: demonstrate that new substances can be made when two or more substances are chemically combined and compare the properties of the new substances to the original substances You can tell a chemical change has occurred if the density, melting point or freezing point of the original substance changes. Many common signs of a chemical change can be seen (bubbles forming, mass changed, etc).

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Characteristics of Physical Changes Melting point Boiling point Vapor pressure Color State of matter Density Electrical conductivity Solubility Adsorption to a surface Hardness

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Definitions Melting point: the temperature at which a given solid will melt.

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Definitions Boiling point: The temperature at which a liquid boils and turns to vapor.

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Definition Volume: The quantity of three-dimensional space enclosed by some closed boundary, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains. Volume is often quantified numerically using the SI derived unit, the cubic meter. LXWXH=V

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Fahrenheit vs Celsius

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Definitions Density: the degree of compactness of a substance. D= m divided by volume degree of consistency measured by the quantity of mass per unit volume.

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Mass Definition: A measure of how much matter is in an object. Mass is commonly measured by how much something weighs. But weight can change depending on where you are (such as on the moon) while the mass stays the same. Mass is measured in grams, kilograms and, tonnes (Metric) or ounces and pounds (US units)

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Weight Definition the force of gravity on the object and may be defined as the mass times the acceleration of gravity, w = mg Gravity= 98.1 m/s2 (meter per second squared)

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Characteristic of Chemical Changes Reaction with Acids Reaction with bases (alkalis) Reaction with oxygen (combustion) Ability to act an oxidizing agent Ability to act as reducing Agent Reaction with other elements Decomposition into simpler Substances Corrosion(corrodes)

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Observations of chemical change Formation of gas (bubbles) Color change Exchange of heat energy (endothermic exothermic reactions) Production of light Precipitate forms

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Examples of Chemical change Burning a log of wood Frying or boiling an egg Photosynthesis - a process in which carbon dioxide and water are changed into sugars by plants Rotting of fruits Roasting a marshmallow Digestion of food Moldy cheese Souring of milk Cracking heavy hydrocarbons to create lighter hydrocarbons Burning of paper Polymerization of gels Different metabolic reactions in the cells Decomposition of waste in a compost pit

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Comparing Physical and Chemical Changes DescriptionIs it Physical?Is it Chemical? Burning coal X Mixing salt & pepperX Dissolving sugar in teaX Melting an iron rodX A can rusting X Cooking scrambled eggs X Water freezing into ice cubesX Fireworks exploding X Sawing wood to make a cabinetX Bread baking X

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Law of conservation of mass Definition: mass is neither created nor destroyed during a chemical reaction it is conserved. Although chemical changes occurred, the total mass involved in the reaction remain constant. Example: If you light a match, it converts the sulfur into gas, and leaves the carbon behind that was there originally, the whole time having the same original mass in the system.

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Composition of Matter Pure substance: usually referred to a substance Definition: matter that has distinct properties and a composition that doesnt vary from sample to sample. Example of pure substance: it can be an element, compound or a mixture.

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Substances Substances are either elements or compounds. Elements: it cannot be decomposed into simpler substances. On the molecular level, each element is compose of only one kind of atoms.

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Elements

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Structure of an atom Protons: positively charged subatomic particle located in the nucleus of an atom. It is counted to identify the atomic number Neutrons : has the same amount of electrons as protons; they are equal. Electrons: negatively charged subatomic particle located in the electron cloud.

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The parts of an atom http://www.iknowthat.com/ScienceIllustratio ns/atoms/science_desk.swf http://www.iknowthat.com/ScienceIllustratio ns/atoms/science_desk.swf

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Compound and Mixtures Compound: substances composed of two or more elements, so they contain two or more kinds of atoms. Mixtures: combinations of two or more substances in which each substance retains its own chemical identity.

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Compound and mixture