Concept explainers
Classify each of the following as aphysicalorchemicalchange or property.
- Milk curdles if a few drops of lemon juice are added to it.
(a)
Interpretation:
Classify the following statement as a physical or chemical change or property.
- Milk curdles if a few drop of lemon juice are added to it.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Milk curdles if a few drops of lemon juice are added to it: chemical change.
Explanation of Solution
On adding the acid in lemon juice, the pH of milk drops, which causes the protein casein molecules to attract one another and form a clump. This curdling of milk is a chemical change which is accelerated in at warmer temperatures than at cold temperatures.
(b)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Butter turns rancid if it is left exposed at room temperature: chemical change.
Explanation of Solution
Butter has fat in it and when fat undergoes oxidation reaction in air it produces a gas that is unpleasant smelling. This how butter turns rancid if it is left exposed at room temperature, which is a chemical change.
(c)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Salad dressing separates into layers after standing: physical change .
Explanation of Solution
Salad dressing is made up on oil, vinegar, salt, pepper and water. Oil and water are immiscible; hence salad dressing separates into layers after standing. Salad dressing is a mixture and it separating into layers after standing is a physical change. There is no change in the chemical composition of the components of a salad dressing.
(d)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Milk of magnesia neutralizes stomach acid: chemical change.
Explanation of Solution
Milk of magnesia is Mg(OH)2, a base, which reacts with HCl in stomach to form a salt MgCl2 Here there is formation of a new product. Hence, milk of magnesia neutralizing stomach acid is a chemical change.
(e)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
The steel in a car has rust spots: chemical change.
Explanation of Solution
Rusting is a chemical redox reaction. Iron in the presence of oxygen in the air and water or air moisture gets converted to hydrated iron(III) oxides Fe2 O.
(f)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
A person is asphyxiated by breathing carbon monoxide: chemical change.
Explanation of Solution
Carbon monoxide binds strongly and irreversibly to the heme protein in hemoglobin. As a result hemoglobin can no longer carry oxygen in the blood. So in the person of carbon monoxide hemoglobin undergoes a chemical change. Therefore, a person is asphyxiated by breathing carbon monoxide is a chemical change.
(g)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Spilled acid burns a hole in cotton jeans: chemical change.
Explanation of Solution
Acids are corrosive and they can break the carbon carbon covalent bonds in cotton fabrics that jeans are made up of. So acids buring a hole in cotton jeans is a chemical change.
(h)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Sweat cools the body as the sweat evaporates from the skin: physical change.
Explanation of Solution
Sweat is in the liquid state. In order to evaporate or get transformed into vapor phase, sweat absorbs heat from the surrounding area on the skin, thereby cooling the whole body.
The transformation of sweat from liquid to gas phase is a physical change.
(i)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Aspirin reduces fever: chemical change.
Explanation of Solution
Aspirin binds to an enzyme COX and inhibits it. Thus preventing COX from producing a high level of prostaglandin, which is an inflammatory agent. Prostaglandin levels are high during and aspirin works to reduce the level of prostaglandin thus reducing pain and inflammation during fever.
(j)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Oil feels slippery: physical change.
Explanation of Solution
Slipperiness of oil is its physical property. There is no change in the chemical composition of the oil.
(k)
Interpretation:
Classify the following statement as a physical or chemical change or property.
Concept Introduction:
Chemical change occurs in a chemical reaction where there is a change in the chemical composition of the substance. In a physical change, there is no change in the chemical composition of the substance but there is a change in the odor, color, melting point etc. of the substance.
Answer to Problem 49AP
Alcohol burns, forming carbon dioxide and water: chemical change.
Explanation of Solution
Combustion of alcohol is a chemical change because after burning alcohol no longer exists but all of it gets converted to carbon dioxide and water.
C2 H5 OH + 3 O2 = 2 CO2 + 3 H2 O.
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Chapter 3 Solutions
Introductory Chemistry: A Foundation
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- Classify the six underlined properties in the following paragraph as chemical or physical: Fluorine is a pale yellow gas that reacts with most substances. The free element melts at 220 C and boils at 188 C. Finely divided metals burn in fluorine with a bright flame. Nineteen grams of fluorine will react with 1.0 gram of hydrogen.arrow_forwardWhich of the following contains an element, a compound, and a mixture? copper, silicon dioxide(SiO2) , copper(II) sulfate(CuSO4) hydrogen, carbon dioxide(CO2) , water(H2O) chili, pizza, steak sodium, sodium chloride (NaCl). salt water nitrogen, argon, airarrow_forwardCategorize each of the following as an element, a compound, or a mixture. (a) sterling silver (b) carbonated mineral water (c) tungsten (d) aspirinarrow_forward
- The following are properties of substances. Decide whether each is a physical property or a chemical property. a Chlorine gas liquefies at 35C under normal pressure. b Hydrogen burns in chlorine gas. c Bromine melts at 7.2C. d Lithium is a soft, silvery-colored metal. e Iron rusts in an atmosphere of moist air.arrow_forwardWhich of the following represent physical properties or changes, and which represent chemical properties or changes? You curl your hair with a curling iron. You curl your hair by getting a “permanent wave” at the hair salon. Ice on your sidewalk melts when you put salt on it. A glass of water evaporates overnight when it is left on the bedside table. Your steak chars if the skillet is too hot. Alcohol feels cool when it is spilled on the skin. Alcohol ignites when a flame is brought near it. Baking powder causes biscuits to rise.arrow_forwardClassify each of the following as element, compound, or mixture. (a) gold (b) milk (c) sugar (d) vinaigrette dressing with herbsarrow_forward
- Classifying Matter Determine whether each of the following is a pure element, a compound, or a mixture. If it is a mixture, classify it as homogeneous or heterogeneous: a. pure salt b. helium gas c. chicken noodle soup d. coffeearrow_forwardFrom the information given, classify each of the pure substances A through D as elements or compounds, or indicate that no such classification is possible because of insufficient information. a. Substance A cannot be broken down into simpler substances by chemical means. b. Substance B cannot be broken down into simpler substances by physical means. c. Substance C readily dissolves in water. d. Substance D readily reacts with the element chlorine.arrow_forwardWhich of the following are pure substances and which are mixtures? For each, list all of the different phases present. a bromine liquid and its vapor b paint, containing a liquid solution and a dispersed solid pigment c partially molten iron d baking powder containing sodium hydrogen carbonate and potassium hydrogen tartratearrow_forward
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