Which Event Always Involves A Chemical Change? Boiling Melting Conducting Burning

Chapter 1. Essential Ideas

1.3 Concrete and Chemical Properties

Learning Objectives

By the end of this section, you will be able to:

Identify properties of and changes in matter every bit physical or chemical
Identify properties of thing every bit extensive or intensive

The characteristics that enable us to distinguish one substance from some other are called backdrop. A physical property is a feature of thing that is not associated with a change in its chemical limerick. Familiar examples of physical properties include density, color, hardness, melting and boiling points, and electric conductivity. Nosotros tin can observe some concrete properties, such as density and color, without irresolute the physical state of the matter observed. Other physical backdrop, such every bit the melting temperature of atomic number 26 or the freezing temperature of water, can but exist observed as matter undergoes a physical change. A physical change is a change in the state or backdrop of matter without any accompanying change in its chemical composition (the identities of the substances contained in the matter). We detect a concrete change when wax melts, when sugar dissolves in coffee, and when steam condenses into liquid h2o (Figure i). Other examples of concrete changes include magnetizing and demagnetizing metals (as is done with common antitheft security tags) and grinding solids into powders (which tin can sometimes yield noticeable changes in color). In each of these examples, at that place is a alter in the physical state, class, or properties of the substance, but no change in its chemical composition.

Figure A is a photograph of 5 brightly burning candles. The wax of the candles has melted. Figure B is a photograph of something being heated on a stove in a pot. Water droplets are forming on the underside of a glass cover that has been placed over the pot.

The change of i blazon of matter into another blazon (or the disability to change) is a chemical holding. Examples of chemical backdrop include flammability, toxicity, acidity, reactivity (many types), and heat of combustion. Iron, for instance, combines with oxygen in the presence of water to form rust; chromium does not oxidize (Figure 2). Nitroglycerin is very dangerous because it explodes hands; neon poses almost no hazard considering it is very unreactive.

Figure A is a photo of metal machinery that is now mostly covered with reddish orange rust. Figure B shows the silver colored chrome parts of a motorcycle. One of the parts is so shiny that you can see a reflection of the surrounding street and buildings.

To identify a chemical holding, we look for a chemical modify. A chemic change always produces one or more types of affair that differ from the thing sspresent before the modify. The formation of rust is a chemical change because rust is a different kind of matter than the iron, oxygen, and h2o present before the rust formed. The explosion of nitroglycerin is a chemical change because the gases produced are very different kinds of matter from the original substance. Other examples of chemical changes include reactions that are performed in a lab (such equally copper reacting with nitric acid), all forms of combustion (burning), and nutrient existence cooked, digested, or rotting (Figure 3).

Figure A is a photo of the flask containing a blue liquid. Several strands of brownish copper are immersed into the blue liquid. There is a brownish gas rising from the liquid and filling the upper part of the flask. Figure B shows a burning match. Figure C shows red meat being cooked in a pan. Figure D shows a small bunch of yellow bananas that have many black spots.

Properties of thing fall into one of ii categories. If the holding depends on the amount of matter present, it is an extensive property. The mass and volume of a substance are examples of extensive properties; for instance, a gallon of milk has a larger mass and volume than a cup of milk. The value of an all-encompassing property is directly proportional to the amount of matter in question. If the property of a sample of matter does not depend on the amount of matter present, it is an intensive belongings. Temperature is an example of an intensive holding. If the gallon and cup of milk are each at 20 °C (room temperature), when they are combined, the temperature remains at 20 °C. As another case, consider the distinct but related properties of heat and temperature. A driblet of hot cooking oil spattered on your arm causes cursory, minor discomfort, whereas a pot of hot oil yields astringent burns. Both the driblet and the pot of oil are at the same temperature (an intensive property), but the pot clearly contains much more than oestrus (extensive belongings).

Hazard Diamond

You may have seen the symbol shown in Figure iv on containers of chemicals in a laboratory or workplace. Sometimes called a "fire diamond" or "hazard diamond," this chemical take a chance diamond provides valuable information that briefly summarizes the various dangers of which to be aware when working with a detail substance.

The diamond is subdivided into four smaller diamonds. The upper diamond is colored red and is associated with fire hazards. The numbers in the fire hazard diamond range from 0 to 4. As the numbers increase, the chemical's flash point decreases. 0 indicates a substance that will not burn, 1 indicates a substance with a flashpoint above 200 degrees Fahrenheit, 2 indicates a substance with a flashpoint above 100 degrees Fahrenheit and not exceeding 200 degrees Fahrenheit, 3 indicates a substance with a flashpoint below 100 degrees Fahrenheit, and 4 indicates a substance with a flashpoint below 73 degrees Fahrenheit. The right-hand diamond is yellow and is associated with reactivity. The reactivity numbers range from 0 to 4. 0 indicates a stable chemical, 1 indicates a chemical that is unstable if heated, 2 indicates the possibility of a violent chemical change, 3 indicates that shock and heat may detonate the chemical and 4 indicates that the chemical may detonate. The lower diamond is white and is associated with specific hazards. These contain abbreviations that describe specific hazardous characteristic of the chemical. O X indicates an oxidizer, A C I D indicates an acid, A L K indicates an alkali, C O R indicates corrosive, a W with a line through it indicates use no water, and a symbol of a dot surrounded by three triangles indicates radioactive. The leftmost diamond is blue and is associated with health hazards. The numbers in the health hazard diamond range from 0 to 4. 0 indicates a normal material, 1 indicates slightly hazardous, 2 indicates hazardous, 3 indicates extreme danger, and 4 indicates deadly.

The National Burn Protection Agency (NFPA) 704 Adventure Identification System was developed past NFPA to provide safety information well-nigh certain substances. The arrangement details flammability, reactivity, health, and other hazards. Within the overall diamond symbol, the pinnacle (reddish) diamond specifies the level of fire hazard (temperature range for flash bespeak). The blue (left) diamond indicates the level of health hazard. The yellow (right) diamond describes reactivity hazards, such as how readily the substance will undergo detonation or a violent chemical change. The white (bottom) diamond points out special hazards, such every bit if it is an oxidizer (which allows the substance to burn in the absenteeism of air/oxygen), undergoes an unusual or dangerous reaction with water, is corrosive, acidic, alkali metal, a biological chance, radioactive, and then on. Each hazard is rated on a scale from 0 to 4, with 0 beingness no hazard and 4 being extremely hazardous.

While many elements differ dramatically in their chemical and physical backdrop, some elements take similar properties. We can identify sets of elements that exhibit common behaviors. For example, many elements bear rut and electricity well, whereas others are poor conductors. These backdrop tin can be used to sort the elements into three classes: metals (elements that bear well), nonmetals (elements that conduct poorly), and metalloids (elements that have backdrop of both metals and nonmetals).

The periodic table is a tabular array of elements that places elements with like properties close together (Figure 4). You will learn more about the periodic table as you go along your study of chemistry.

On this depiction of the periodic table, the metals are indicated with a yellow color and dominate the left two thirds of the periodic table. The nonmetals are colored peach and are largely confined to the upper right area of the table, with the exception of hydrogen, H, which is located in the extreme upper left of the table. The metalloids are colored purple and form a diagonal border between the metal and nonmetal areas of the table. Group 13 contains both metals and metalloids. Group 17 contains both nonmetals and metalloids. Groups 14 through 16 contain at least one representative of a metal, a metalloid, and a nonmetal. A key shows that, at room temperature, metals are solids, metalloids are liquids, and nonmetals are gases.

Key Concepts and Summary

All substances have distinct concrete and chemical backdrop, and may undergo physical or chemical changes. Physical properties, such as hardness and boiling bespeak, and physical changes, such every bit melting or freezing, exercise not involve a alter in the composition of matter. Chemical backdrop, such flammability and acidity, and chemic changes, such as rusting, involve production of matter that differs from that present beforehand.

Measurable backdrop fall into i of 2 categories. All-encompassing backdrop depend on the amount of affair nowadays, for example, the mass of gold. Intensive properties do not depend on the amount of matter present, for example, the density of gold. Heat is an example of an extensive property, and temperature is an instance of an intensive holding.

Chemistry Cease of Chapter Exercises

Allocate the six underlined properties in the following paragraph equally chemic or physical:
Fluorine is a pale yellow gas that reacts with about substances. The gratuitous element melts at −220 °C and boils at −188 °C. Finely divided metals burn down in fluorine with a bright flame. Nineteen grams of fluorine will react with 1.0 gram of hydrogen.
Classify each of the post-obit changes as physical or chemical:
(a) condensation of steam

(b) burning of gasoline

(c) souring of milk

(d) dissolving of sugar in h2o

(e) melting of gold
Classify each of the following changes as physical or chemical:
(a) coal burning

(b) ice melting

(c) mixing chocolate syrup with milk

(d) explosion of a firecracker

(e) magnetizing of a screwdriver
The volume of a sample of oxygen gas changed from x mL to 11 mL every bit the temperature changed. Is this a chemical or concrete modify?
A 2.0-liter volume of hydrogen gas combined with one.0 liter of oxygen gas to produce two.0 liters of water vapor. Does oxygen undergo a chemic or concrete modify?
Explain the difference betwixt extensive properties and intensive properties.
Identify the post-obit backdrop as either extensive or intensive.
(a) volume

(b) temperature

(c) humidity

(d) heat

(e) boiling point
The density (d) of a substance is an intensive property that is defined as the ratio of its mass (m) to its volume (5).
[latex]\text{density}= \frac{\text{mass}}{\text{volume}}[/latex] [latex]\text{d} = \frac{\text{thousand}}{\text{V}}[/latex]

Considering that mass and volume are both extensive properties, explain why their ratio, density, is intensive.

Glossary

chemical change: modify producing a different kind of affair from the original kind of matter

chemical property: behavior that is related to the modify of one kind of thing into another kind of thing

all-encompassing property: property of a substance that depends on the corporeality of the substance

intensive property: property of a substance that is independent of the corporeality of the substance

physical change: change in the land or properties of matter that does not involve a change in its chemic composition

physical property: characteristic of affair that is not associated with any change in its chemical limerick

Solutions

Answers for Chemical science End of Chapter Exercises

2. (a) concrete; (b) chemical; (c) chemical; (d) physical; (e) physical

iv. concrete

6. The value of an all-encompassing property depends upon the amount of matter beingness considered, whereas the value of an intensive belongings is the same regardless of the corporeality of affair beingness considered.

eight. Being extensive properties, both mass and book are directly proportional to the corporeality of substance under study. Dividing one extensive belongings by another will in effect "cancel" this dependence on corporeality, yielding a ratio that is independent of amount (an intensive property).