Physical & Chemical Changes Changing Matter Physical & Chemical Changes

What different ways can we differentiate between people? Properties How we identify something. All substances have properties that we can use to identify them. For example we can identify a person by their face, their voice, height, finger prints, DNA etc.. The more of these properties that we can identify, the better we know the person. In a similar way matter has properties - and there are many of them. There are two basic types of properties that we can associate with matter.

Matter has properties Two basic types of properties that we can associate with matter. Physical properties Chemical properties

Physical Properties Anything that can be observed without changing the identity of the substance. (Tends to be measurable.) melting point density boiling point thermal conductivity electrical conductivity ductility color malleability

Malleability The ability of an object to be molded into different shapes. Example – metals. Opposite – Brittle, not flexible.

Ductility The ability of an object to be drawn into thin wires without losing strength. Metals are ductile.

Combustion - the process of burning something Chemical Properties The way a substance may change or react to form other substances combustion Reactivity to other chemicals reactivity with water PH Oxidation Flammability Chemical properties of matter describes its "potential" to undergo some chemical change or reaction by virtue of its composition. What elements, electrons, and bonding are present to give the potential for chemical change. It is quite difficult to define a chemical property without using the word "change". Eventually you should be able to look at the formula of a compound and state some chemical property. At this time this is very difficult to do and you are not expected to be able to do it. For example hydrogen has the potential to ignite and explode given the right conditions. This is a chemical property. Metals in general have they chemical property of reacting with an acid. Zinc reacts with hydrochloric acid to produce hydrogen gas. This is a chemical property. Combustion - the process of burning something

Matter can be changed two ways Physically Physical reaction Physical change Chemically Chemical reaction Chemical change

Physical Changes Do NOT CHANGE THE TYPE OF MATTER Nothing new or different is formed Could be a change in: Mass Volume Density Change in state Color Shape Size

Physical Changes Substance may seem different, but the way the atoms link up is the same. It changes phase (freezes, boils, evaporates, condenses, sublimates)

Examples of Physical Changes Boiling Freezing Dissolving Breaking Making a mixture 2 or more types of matter (substances) mixed together Not in specific amounts Can be separated physically

Chemical Changes Chemical changes, or chemical reactions, are changes that result in the production of another substance.  Changes the way the molecules link up (chemical composition) Makes new substances (new compounds, or compounds are broken down into the elements that make them up) The substances present at the beginning of the change are not present at the end; new substances are formed. The change cannot be “undone.”

Chemical Changes Evidence of a chemical reaction Formation of gas Formation of precipitate Change in color Change in energy (temperature) Endothermic Absorbs heat energy (gets cold) Exothermic Releases heat energy (gets hot) Alka-Seltzer: (Baking soda or sodium bicarbonate) NaHCO3 + Citric acid ---> CO2 + H2O + Sodium Citrate

Chemical Changes Atoms are re-arranged, NOT created or destroyed

It’s a chemical change if…. It burns Temperature changes without heating/cooling

It’s a chemical change if…. It bubbles (makes a gas)

It’s a chemical change if... It changes color It forms a precipitate – (solid that forms from two liquids).

Again signs that a Chemical Change has occurred Creation of a gas (bubbles) Creation or loss of heat Fire Rotting Breaking down (decomposition) Precipitation (Sour milk clumps) Cooking Rusting (oxidation)

Chemical Change The only TRUE sign that a chemical change has taken place is the formation of a new substance. A new substance that was not there before. A new substance with a new chemical composition (Atoms are arranged differently).

Basically What You’re Telling Me Is… If you end up with a chemical or chemicals that you did not start with, It is a chemical change!!!!!!!

Another Example Is… Eating… Now eating can change food both physically and chemically. Chewing is Physical but… Once the food touches the chemicals in the saliva begin to change the food chemically.

Law of Conservation of Matter Matter is conserved  type of atoms does not change Nothing is created or destroyed

Law of Conservation of Mass Mass is conserved  amount of atoms cannot change Nothing is created or destroyed

What kind of change is it if someone... Tears up paper? Physical change Mixes salt and water?

What kind of change is it if someone... Burns paper? Chemical change Evaporates salt water? Physical change

What kind of change is it if someone... Mixes vinegar and baking soda? Chemical change

Physical and Chemical Changes Quiz ……….True or False??   1. With a physical change, no new substance is formed.   2. With a chemical change, a chemical reaction occurs. 3. With a physical change, energy is either given off or absorbed. 4. A chemical change can be easily reversed. 5. Eating food can be considered both physical and chemical changes.

Physical and Chemical Changes Quiz……….Answers! 1. With a physical change, no new substance is formed.  TRUE 2. With a chemical change, a chemical reaction occurs. TRUE 3. With a physical change, energy is either given off or absorbed. FALSE 4. A chemical change can be easily reversed. FALSE 5. Eating food can be considered both physical and chemical changes. TRUE

ONLINE QUIZ http://www.fordhamprep.org/gcurran/sho/sho/review/rev15b.htm

Physical or Chemical Change? Painting Wood PHYSICAL

Physical or Chemical Change? A ring tarnishing CHEMICAL

Physical or Chemical Change? Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, magnesium and other similar metals as their outermost layer undergoes a chemical reaction. It causes to lose luster.

Physical or Chemical Change? Burning Paper CHEMICAL

Physical or Chemical Change? Digestion of food CHEMICAL

Sugar dissolving in water PHYSICAL Physical or Chemical Change? Sugar dissolving in water PHYSICAL

Iron turning red when heated PHYSICAL Physical or Chemical Change? Iron turning red when heated PHYSICAL

Physical or Chemical Change? Evaporation PHYSICAL

A pond freezing in winter PHYSICAL Physical or Chemical Change? A pond freezing in winter PHYSICAL

Physical or Chemical Change? Melting ice PHYSICAL

Physical or Chemical Change? Cutting wire PHYSICAL

Physical or Chemical Change? Painting fingernails PHYSICAL

Physical or Chemical Change? Cutting fabric PHYSICAL

Physical or Chemical Change? Baking muffins CHEMICAL

Physical or Chemical Change? Shattering glass PHYSICAL

Decomposition of old leaves CHEMICAL Physical or Chemical Change? Decomposition of old leaves CHEMICAL

Physical or Chemical Change? Wrinkling a shirt PHYSICAL

Physical or Chemical Change? An old nail rusting CHEMICAL