Chemical and Physical Properties
Observe the solubility in hot water. c. Tear off approximately 1/2-cm pieces of both red and blue litmus paper. d. Allow the solution to cool, and using the glass stirring rod, transfer a drop of the solution onto a piece of litmus paper. Record the results. Clean the stirring rod. 5. Third test tube: a. Add a few pipet drops of HCl (hydrochloric acid) to the sample and stir. NOTE: Use the test tube holderclamp as some reactions are exothermic, i. e. the test tube may get very hot. Record any apparent reaction or solubility. Clean the stirring rod. 6.
Fourth test tube: Add a few pipet drops of NaOH (sodium hydroxide) to the sample. Stir. Record any apparent reaction or solubility. Clean the stirring rod. 7. Thoroughly clean and dry all 4 test tubes. Repeat Steps 2 though 6 with the next substance. Experimental Results Substance: Zn Color: Grey Odor: None Effect of Heat: decreases content curled in with lighter color Solub. Or Reaction w/cold H20: No reaction observed / not soluble Solub. Or Reaction w/ hot H20: Prolonged boiling from retained heat/ non soluble Litmus test: None observed
Dilute HCI: positive reaction resulting in the formation of gas, carbonation, and darkened Dilute NaOH: creates foggy substance and blackens solid Substance: Cu Color: Copper Odor: None noted Effect of Heat: Turned black Solub. Or Reaction w/cold H20: not soluble Solub. Or Reaction w/ hot H20: not soluble Litmus test: None observed Dilute HCI: tarnished not observed Dilute NaOH: none observed Substance: Mg Color: Silver Odor: None observed Effect of Heat: increases in dullness Solub. Or Reaction w/cold H20: no reaction observed/ non soluble Solub.
Or Reaction w/ hot H20: increased heat / non soluble Litmus test: no change Dilute HCI: rapid boiling and heat Dilute NaOH: liquid is cloudy Substance: MgO Color: White Odor: None observed Effect of Heat: none observed Solub. Or Reaction w/cold H20: Soluble Solub. Or Reaction w/ hot H20: Soluble Litmus test: Red paper turned blue / blue no reaction Dilute HCI: Carbonated Soluble Dilute NaOH: Dense Soluble Substance: CuC03 Color: Green Odor: pungent Effect of Heat: turned black Solub. Or Reaction w/cold H20: slightly murky, but does not appear soluble
Solub. Or Reaction w/ hot H20: slightly murky, but none soluble Litmus test: changes blue to red showing slight acidity Dilute HCI: carbonation and soluble Dilute NaOH: turns blue w/ slight soluble Substance: Cu(NO3)2 Color: Blue crystals Odor: slight odor Effect of Heat: melted and turned green Solub. Or Reaction w/cold H20: turned water blue and is soluble Solub. Or Reaction w/ hot H20: no change observed from the cool water and is soluble Litmus test: blue litmus turned to red for acid Dilute HCI: turned green Dilute NaOH: soluble formed Substance: NaCl
Color: white crystals Odor: none observed Effect of Heat: none noted Solub. Or Reaction w/cold H20: becomes slightly soluble Solub. Or Reaction w/ hot H20: fully soluble Litmus test: red turns to blue indicating that it’s basic Dilute HCI: none observed Dilute NaOH: none observed QUESTIONS: A – Did you observe any chemical changes in this experiment? Chemical changes are observed during the experiment B – What evidence did you use to decide that something was a chemical change? Indications of chemical changes were preceded by the burning, rusting, ermenting, and decomposing of the substances. As a result, a new substance will have its own unique physical properties C – Give at least two examples of chemical changes you observed. Adding colorless sodium hydroxide to blue copper(II) nitrate produces a light blue precipitate Zinc diluted with Hydrogen Chloride is positive for a chemical reaction resulting in the formation of gas, carbonation, and darkened D – Classify the following properties of sodium metal as physical or chemical: Silver metallic color – physical Turns gray in air – chemical Melts at 98oC – physical
Reacts explosively with chlorine – chemical E – Classify the following changes as physical or chemical: Water freezes at OoC – physcical change Baking soda when combined with vinegar produces bubbles:- chemical change Mothballs gradually disappear at room temperature – physical change Ice cubes in a freezer get smaller with time – physical change Baking soda loses mass as it is heated – physical chemical Tarnishing of silver – chemical change F – How would you show that dissolving table salt is a physical change? A physical change will not change the composition of a substance.
When adding water to a salt, the ions of table salt are hydrated with water molecules which reduced the strong electrostatic forces of the ions. To return salt to the original state, simply remove the hydrated water molecules by boiling the table salt. Conclusions: In a chemical change one or more new substances are formed. The new substance has its own unique identity which is different from the original. It has properties that are different than those of the starting material; in addition, the original materials is not able to be reproduced by physical means.