Chemical and Physical properties and changes

Chemical changes

1. a chemical change can't be reversed 2. In a chemical change where there is a chemical reaction, a new substance is formed and energy is either given off or absorbed. e.g. If the piece of paper is burned, it is broken up into different substances that are not paper. 3. If one made a recipe for a cake with flour, water, sugar and other ingredients and baked them together, it would take extraordinary means to separate the various ingredients out to their original form.

Physical changes

1. a physical change can be reversed e.g. water>ice>water 2. A physical change in a substance doesn't change what the substance is. e.g. if a piece of paper is cut up into small pieces it still is paper. This would be a physical change in the shape and size of the paper. 3. If one decided to mix sugar into water to make sugar water, this would be a physical change as the water could be left out to evaporate and the sugar crystals would remain.

Identify the observable indicators that can be evidence a chemical change might have occurred

1. change in temperature 2. change in color 3. noticable odor (after reaction has begun) 4. formation of bubbles 5. Formation of a precipitate. (formation of a solid)

chemical change

A change that occurs when one or more substances change into entirely new substances with different properties. (related word: chemical reaction)

Chemical properties

Chemical properties 1. Acidity 2. Reactivity with water 3. Heat of combustion (usually can't be reversed, molecular make up changes) Chemical properties are very different from physical properties. To determine chemical properties of a substance, the substance must be altered in some way. Chemical properties include reactivity, toxicity, flammability, stability, and many others. The way atoms bond, and the types of bonds atoms form, help determine chemical properties. Many chemical properties can also be observed during chemical reactions.

phase of matter

Phases of ordinary matter are determined by pressure and temperature. e.g. ice (solid) melts into water (liquid) due to the addition of heat. At high temperatures, or due to application of a magnetic field, matter becomes plasma. The 4 phases of matter are: 1. solid 2. liquid 3. gas 4. plasma

Physical properties

Physical properties 1. Color 2. Density 3. Boiling point (molecular make up of molecules doesn't change) Physical properties are any properties of matter that can be measured or observed without changing or altering the chemical identity of matter. Physical properties are used to describe matter. Color, texture, density, boiling point, melting point, freezing point, odor, appearance, solubility, and polarity, are just some of the common physical properties of matter. These properties can be determined without changing the composition of the matter being tested.

physical change

a change in only the appearance of matter, usually from one phase of matter to another, that does not affect the chemical composition of the substance. Matter can change from liquid to solid (freezing or solidification); from liquid to gas (evaporation)

chemical property

a characteristic of a substance that is measurable or observable during a chemical reaction; includes pH, heat of combustion, reactivity, etc.

physical property

a characteristic that can be observed (intensive), such as texture, color, odor, melting point, boiling point, density, or measured (extensive) such as mass, length, volume, that is used to describe matter and can be observed or measured without changing its composition

extensive properties

a property that depends on the size of an object or system e.g. The mass of an iron rod is an extensive property because it depends on the size of the rod. The volume of the rod is another extensive property.

precipitate

a solid that forms and settles out of a liquid mixture (solid particles that have been separated from a solution)

intensive property

features of substances that do not vary with quantity - Intensive properties include hardness, density, boiling point, melting point, freezing point, and solubility. e.g. if you have a cup of sugar, intensive properties are that it is white, sweet, solid (because if you take away half a cup, it will still be the same)