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1314.2 Physical and Chemical Properties

The Chemistry of a CampfireA fire can be fascinating to watch (Figure 4.16). Although all the flames may look similar, each particular spark or flicker isunique—never repeating in exactly the same way.

From an Elder’s point of view, the gathering of wood is animportant first step in building a campfire. Historically, wood wasnot readily available on the Saskatchewan plains. First Nationspeople burned buffalo dung to make fire. To start a fire, a bowdrill was used. It is a horizontally positioned bow with itsdrawstring wrapped about a thick stick that rubs against smallerpieces of wood, called kindling. The sawing motion of the bowcreates friction on the kindling, which ignites it.

From a scientist’s point of view, investigations on lighting afire demonstrate some clear patterns. Every fire needs the samethree components to get started: fuel, oxygen gas, and heat.Scientists work toward developing generalized explanations ofphenomena. In a scientific explanation of a campfire, the fuel istypically wood, a complex natural material that is rich in carbon.Carbon reacts with oxygen in the air, but only if the air can reachthe carbon in the wood. The first step in building a campfire isusually to split a log into kindling. By chopping a thick log intosmaller pieces, much more carbon in the wood is exposed to theair. Oxygen gas has easy access to the carbon at the surface of the wood and so can react with it.

Here is a summary of what youwill learn in this section:

• Physical properties describethe characteristics of asubstance that can beobserved or measured.

• Chemical properties describethe chemical reactivity of asubstance and ways in which it forms new substances.

• Physical properties includesmell, colour, melting point,boiling point, density, solubility,conductivity, hardness, lustre,texture, and malleability.

• Chemical properties includecombustibility and reactionwith water or acid.

Physical and Chemical Properties

Figure 4.16 A fire produces many changes in matter.

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More on an Elder’s View of a Fire

First Nations people mightshow respect to Mother Earthby sprinkling some tobacco on the ground where the woodfor a fire is found, in thanks for the gift of fire that the woodwill bring. They understandthat Fire is a Spirit. When oneblows on a fire, one preventsFire Spirit from doing its workand is a sign of disrespect. As a result, Elders, KnowledgeKeepers, and helpers will never blow on a fire. Duringtraditional ceremonies,whenever a fire is lit, or whenmatches are used, they allow a fire to burn out on its own.

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4.2

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The components of a fire must be in just the right balance.When lighting a fire, extra oxygen is sometimes needed. Gentleblowing on the first embers of the fire can help. There is enoughoxygen in the breath to provide an extra boost. It is important not to blow the heat energy of the first sparks away from the fuel,as this will blow out the fire. Since combustion releases heatenergy, there is no need to keep relighting the flame.

132 UNIT B Atoms and Elements©P

B4 Quick Science

Soda pop contains carbon dioxide. In the air, carbondioxide exists as a gas. However, when carbon dioxidedissolves in water, this is not the case. The particles ofwater and carbon dioxide are attracted to each other,so they intermix, forming a solution. Disrupting theseattractions produces a change that you will observe.

When a substance undergoes a physical change,such as melting, its appearance or state may change,but its composition stays the same. For example,melted chocolate ice cream has the same compositionas frozen chocolate ice cream. In contrast, a chemicalchange results in the formation of a new substanceor substances with different properties.

PurposeTo investigate a change in matter

Observing a Physical Change

2. Into one glass, drop a piece of mint candy.Observe what happens in both glasses, and record your observations.

Questions3. Adding candy to the soda pop caused a mainly

physical change that disrupted the attractionbetween particles of liquid. How did yourecognize this physical change?

4. Can you tell whether the composition of thecandy changed after it was added to the sodapop? Why or why not?

5. Consider the change that took place. Suggestone reason that you would describe it as aphysical change. Suggest one reason that youmight also describe it as a chemical change.

6. In the procedure, you were instructed to fill twoglasses with soda pop in step 1 but to add candyto only one glass. What is the reason for this?

7. Suggest ways to modify the procedure toproduce an interesting effect or display involvingthe change in properties. Check with yourteacher before trying it out.

Pose New Questions8. How many changes, both physical and chemical,

are involved in this activity? What are they andwhat vocabulary would you use to describe the changes?

CAUTION: Do not eat or drink anything in the lab,including the soda pop and candy.

• two drinking glasses

• soda pop

• chewy mint candy

Materials & Equipment

Procedure1. Fill each of the two glasses about two-thirds full

with soda pop.

04_sk_sci9_se_ch04:Layout 1 3/26/11 2:49 PM Page 132

Physical Properties of WaterAll life on Earth depends on water. As depicted by the Nakawe–

story of creation, water was one of the four elements that arosefrom the Woman’s Spirit heart. Among all First Nations andMétis peoples, water is sacred and is treated with great respect.

Our bodies are about 70 percent water. Some plants are 95 percentwater. A characteristic of water is that it sticks to itself, a propertyscientists call cohesion. Due to cohesion, water forms beads onnon-absorbent surfaces, such as glass. Water also sticks to othersubstances, a property scientists call adhesion (Figure 4.17). A towel is able to mop up water by using this property of water.

A physical property describes a characteristic of a substancethat can be observed or measured without changing its composition.Water has many interesting physical properties that make it very useful to organisms. One example is being a liquid at roomtemperature. Also, the properties of adhesion and cohesion helpmove water up through the stems of plants, including tall trees.

Most materials shrink when they freeze. Water does not.Because of the special arrangement of water particles duringfreezing, water actually expands. This makes ice less dense thanliquid water. As a result, ice floats on water. Why is this important?In winter, the ice on a body of water shelters the fish below.Floating ice can also make a useful temporary roadway or platformfor ice fishing (Figure 4.18). However, the same properties thatmake water useful can also cause problems. As ice forms, itwidens cracks in roads. In addition, snow and ice on the roofs of houses can cause damage due to melting and refreezing. Notonly is the ice heavy, it can block gutters and downspouts that are meant to keep water flowing off the roof and away from thesides of a building.

Observing Physical PropertiesFigure 4.19 shows a dull, red, clouded piece of beach glass. Threephysical properties of the glass include its lustre (shiny or dull),its colour, and its transparency (how much light it allows through).Other physical properties can be observed using appropriate toolsor measuring devices. For example, in grade 8, you measured themass and the volume of objects and fluids to determine theirdensities. Table 4.1 on the next page lists a number of otherphysical properties.

1334.2 Physical and Chemical Properties©P

Figure 4.17 Water sticks to itself,forming droplets (cohesion), and to the spider web (adhesion).

Figure 4.18 In winter, fish areprotected from freezing temperaturesby the ice at the surface of the water.People can use this same ice as aplatform when fishing.

Figure 4.19 The pieces of beach glassshow a variety of physical properties.



Property Description Examples What It Looks Like

Colour and lustre Colour is the firstappearance of a substance.Lustre (shine) is the way the surface of a substancelooks in the light.

The names for some substances, such as gold,are also the names ofcolours. Gold has lustre;concrete is dull.

Gold andsilver coins are very lustrous.

Melting point Melting point is thetemperature at which a solid changes into a liquid. It is the same temperatureas the freezing point of the same substance from a liquid to a solid. Melting point is affected by atmospheric pressure.

The melting point of ice at average sea-levelatmospheric pressure is 0°C.Water freezes at 0°C.

Solid watermelts at 0°C.

Boiling point Boiling point is thetemperature at which aliquid changes into a gas. It is the same temperatureas the condensation point ofthe same substance from agas to a liquid. Boiling point,like melting point, is affectedby atmospheric pressure.

The boiling point of water at average sea-levelatmospheric pressure is 100°C.

Water boilsat 100°C.

Density Density is the amount ofmass in a given volume of a substance. Density isaffected by temperature.

At 25°C, the density of purewater is 1 g/mL. The densityof gold is 19 g/mL. Water isdenser than oil, but gold isdenser than water.

Fluids andsolids withdifferentdensities

Solubility Solubility is the maximumamount of substance thatcan dissolve in water. Thesolubility of a substance is affected by thetemperature of water.

The solubility of pure salt (sodium chloride) is 35 g/100 mL of water at 0°C.

Chocolatepowderdissolves fastin hot water.

Ductility Any solid that can bestretched into a long wire is said to be ductile.

Copper is a commonexample of a ductilematerial.

The ductility of copper allows it to become thin wire.

Table 4.1 Physical Properties of Matter



Property Description Examples What It Looks Like

Crystal shape When particles in asubstance line up in aregular pattern, smoothsurfaces and sharp edgesare created to give thecrystal shape of thesubstance.

The rock mineral quartzforms long, six-sided crystals and halite (rock salt) forms cubes.

A quartz crystal showing smooth surfaces and sharp edges

Conductivity Conductivity is the ability of a substance to conductelectricity or heat energy. A substance that conductselectricity or heat energy is called a conductor. Asubstance with little or noconductivity is an insulator.

Most metals are goodconductors. Copper is a very good conductor ofelectricity and so is used to make electric wires.Styrofoam™ and glass are insulators.

Electric circuitwith copper wires to conduct electricity

Hardness Hardness is a substance’sability to resist beingscratched. Hardness isusually measured on theMohs hardness scale from 1 to 10.

The mineral talc is thesoftest substance on theMohs hardness scale (1).Emerald is quite hard (7.5).Diamond is the hardest (10).

An emerald gemstone is fairly scratch resistant.

Texture Texture is described as the feel of the surface of a substance.

The surface of a rawgemstone usually feelsrough when it is mined. The surface can becomesmooth after having beencut and polished.

Raw diamond has a rough surface until it has been cut and polished.

Malleability A substance that can bepounded or rolled intosheets is said to bemalleable.

Aluminum foil is an example of a malleablesubstance. Metals such as gold and tin are alsomalleable.

Aluminum foil is easily shaped andmoulded since it is highly malleable.


Observing Chemical PropertiesA chemical property is a characteristic of a substance thatdescribes how it reacts when it changes into a new substance orsubstances. The change may occur when the substance interactswith other substances, such as acids, or when the substance isexposed to heat energy or light. A chemical change alwaysresults in the formation of a new substance or substances with different properties. For example, when zinc metal andhydrochloric acid are mixed, they undergo a chemical change that produces two new substances: hydrogen gas and a compoundcalled zinc chloride. A chemical reaction is a process in which achemical change occurs.

Chemical properties can be observed only when a chemicalchange occurs. If you mix baking soda and vinegar, as in InquiryActivity B2 on page 128 and Quick Science B3 on page 130, youwill produce a chemical change that involves the formation of gas bubbles. In general, evidence of chemical change can includecolour change, odour, temperature change, the production of light,the formation of a new solid inside a liquid, or the production of anew gas (Figures 4.20 and 4.21). However, observing any or all ofthese properties does not guarantee that a chemical reaction hasoccurred. Table 4.2 lists various chemical properties.


Figure 4.20 Chemical changes madethis banana ripe—and then rotten.

Suggested Activities •B6 Inquiry Activity on page 142B7 Inquire on Your Own on page 144

Figure 4.21 Fireflies contain a chemical called luciferin. When luciferin reacts with oxygen,light is emitted.

Chemical Properties

Absorbs heat during reaction

Combustible

Forms gas when heated

Reacts with acid

Reacts with water

Emits heat energy duringreaction

Emits light during reaction

Forms a precipitate (solid) in a solution

Table 4.2 Examples ofChemical Properties


Learning Checkpoint

1. Describe the first step in building a campfire from an Elder’s point of viewand from a scientist’s point of view.

2. What is a physical property? List three physical properties of water.

3. What is a chemical property? List three examples of chemical properties.

4. How does a physical change differ from a chemical change?

5. What kind of ideas do scientists usually develop? Give an example.

Heat and Chemical ChangeHeating a substance can result in chemical changes. For example,when baking soda is heated, it undergoes a chemical change thatresults in the production of carbon dioxide gas. This is very usefulin cooking. It is this chemical reaction of baking soda in somebaked foods that produces the gas needed to lift the cake andmake it light and fluffy (Figure 4.22). If you forget to add bakingsoda to a cake batter, the cake will be flat and dense.

Heating causes many different kinds of substances to react.Burning is an example of this kind of chemical change. Paper iscombustible. When a flame or spark is applied, the heat energystarts the reaction of paper with oxygen to produce heat energy,light, carbon dioxide, and water. Once the reaction has started, it gives off enough heat energy to keep the paper burning.Combustibility is the ability of a substance to react quickly with oxygen to produce heat energy and light.

When some substances are mixed,their reaction absorbs heat energyfrom the surroundings. A chemicalcold pack, for example, depends on a reaction that absorbs heat energy(Figure 4.23). Typically, a chemicalcold pack is filled with water but also has an inner bag or tube full ofchemicals. The inner compartmentkeeps its contents separated from thewater until it is time to use the coldpack. When the inner bag is poppedopen, the chemicals within mix with the water in the cold pack. The reaction absorbs heat energy from the surroundings, and so the pack feels cold to the touch.


Figure 4.22 When baking soda in acake batter is heated, it produces a new substance: a gas.

Understanding Vocabulary

Authors often provideadditional information—called an “elaboration”—tohelp you understand a newterm or word. As you findnew terms or expressions,look not just for a definitionbut also for added informationthat clarifies the term.

During Reading

water

chemicals that willreact with water

Figure 4.23 A chemical cold pack has an inner compartment containingreactive chemicals and an outercompartment containing water.


Ask an Elder

Julie Pitzel: Birch Syrup, a Traditional Use of the Land

Elder Julie Pitzel is a Métis Elder of Dené, Cree,Scottish, and French descent. She is a retiredprincipal who lives and works as a counsellor for a healing lodge. She teaches life skills from a traditional perspective at the Métis AddictionsCouncil of Saskatchewan in the city of PrinceAlbert. Growing up in the community of BuffaloNarrows in northern Saskatchewan, Elder Julielearned the traditional ways of her family on thetraplines where they caught muskrat, beaver, wolf, otter, weasel, and fish.

Elder Julie came to know many importantteachings and skills on the traplines. By hergrandmother’s and grandfather’s side, she learnedto make lye soap, to smoke fish, to tan hides, andto produce birch syrup. All are gifts from the land.

When we think of syrup, often maple trees cometo mind. However, in Elder Julie’s community,where birch trees are abundant, syrup was madefrom their sap. To make birch syrup requires a lotof patience, she explains. After a grove of suitabletrees is found, the trunks are tapped using a sharpnail, knife, or stick, and the sap is allowed to flowfreely (Figure 4.24). A pail hanging by a branchcatches the sap. In earlier times, Elder Julieexplains, her people used a birch bark basketinstead of a pail. This sap must be made intosyrup. A shallow hole with a small circumferenceis dug into the earth and fire is made inside it.Sticks of 20 cm in length are placed above thefire, far enough so that they do not burn tooquickly. An iron pot filled with sap is placed on thesticks over the fire and boiled until thick rich syrupis made. To decide on the quality of the syrup’sconsistency, a soup ladle of syrup is slowly pouredback into the pot to see what the syrup looks like.

Figure 4.24 A deep cut is made in this birch trunk and a V-shaped tab of bark is pulled out to collect the sap.


Before iron pots were available, Elder Julie’speople heated stones over the fire and these wereplaced into the syrup in the birch bark baskets.The gooey solution took a long time to makebecause as these heated stones cooled, theyneeded to be replaced with hot ones.

Not all Indigenous communities make birchsyrup the same way. Elder Julie describes a method that works well with birch trees in theBuffalo Narrows area, but environmentalconditions could be quite different in othercommunities. The method she describes workswell in one place, but not necessarily in all places.This type of understanding is called “place-basedknowledge.” We learn place-based knowledge from Elders. From generations of experience, place-based knowledge is perfected. Scientists,however, try to produce ideas that work in allplaces. For example, they use the idea that matteris made of particles to explain the physical andchemical properties of matter. Scientists worktoward developing “generalizable knowledge.” To do this, scientists must sometimes ignore unique features of one particular place.

Traditional life required much understanding,patience, and hard work. Knowledge about theland and its gifts allowed First Nations and Métispeoples to survive the harsh Saskatchewan climate.


Controlling Changes to MatterIn our daily lives, there are many examples of howunderstanding and controlling changes in matterhelp us meet our basic needs. Being able to changematerials from one form to another allows us tomake products that are not only useful but that alsosupport a sustainable environment. For example,chemicals made from corn can be used to makejuice bottles, remove paint or nail polish, and fuelsome cars. Corn is put through a chemical changecalled fermentation. Once this chemical process is complete, thenew substances are recovered, purified, and made into solvents(Figure 4.25), biodegradable plastics, and automobile fuel.

An advantage of corn-based biodegradable plastics is that they can be broken down by bacteria. However, making and using corn-based products also has its drawbacks. Peoplesometimes cut down rainforests to make way for cornfields. Corn that would otherwise be used for food is sometimes diverted to make disposable products.

Traditional Uses of SubstancesFirst Nations people understood details about properties of matterwithout knowing the scientific ideas of physical and chemicalchanges. Their ideas about the physical world served them very well. Their way of knowing and the scientific way do notcontradict each other. Both add to humanity’s understanding.

Preservation of FishUnderstanding matter and its manytransformations allowed First Nationspeople to prevent spoilage and allowedthem to store meat which wouldotherwise quickly rot in the heat ofsummer. Dehydrating meats was a meansto slow down bacterial decomposition.An example of this important process isthe preservation of fish (Figure 4.26).According to the Elders, whitefish,jackfish, and occasional red sucker fishmade up a large part of their diet. Topreserve these fish, they are smoked.


Figure 4.25 The inks used herecontain solvents made from corn.

Suggested Activity •B5 Science, Technology, Society, and the Environment on page 141

Many of the items you used today are made frompolyethylene. Research to findout what these polyethyleneplastics are. Adding cornstarchto plastic is one way to makethe plastic biodegradable. Find out about other “green”products by doing researchusing the Internet.

reSearch

Figure 4.26 The skills of preserving fish allowed First Nations people to store their catch in the summer for eating in the winter.


An Ancient Skill

Rock paintings created by First Nations people along the Churchill River in northernSaskatchewan are believed to be hundreds of years old.They used ochre, a reddish-brown mineral, to give colourto their paint. Ingeniously,these people also knew how to stop their paintings fromfading over time due toexposure from water and theSun. They made a gelatin-likesubstance, called “isinglass,”from dried swim bladders offreshwater fish and mixed itwith ochre to add to the paint.

infoBIT First, the scales are removed and the fish prepared. With a sharpknife, a cut is made from the head, along the length of the backtoward the tail. The tail is kept intact. After the fish is split open (still in one large filet), the organs and bones are removed.Lengthwise and widthwise cuts are made into the flesh to form small squares.

A lean-to, shaped like a tripod, is fashioned out of wood andlashed together. A shelf of sticks is built near the top where thepoles of the lean-to meet. A fire is lit under the lean-to beneaththe shelf. Old dried poplar wood produces the best smoke. Often it takes two days for the fish to be completely smoked and readyto eat. Smoking fish ensured that the First Nations people couldpreserve their catch for a few days in the summer or for eatingduring the winter.

MedicineThe healing tradition of the First Nations and Métis peoples is a holistic process that includes physical, mental, emotional, andspiritual healing. Herbal medicines in combination with prayerand ceremony have been used by First Nations and Métis peoplesof Saskatchewan for many generations. The herbs used could be aplant or part of a plant or a substance extracted from a plant suchas a sap or an oil (Figure 4.27). A herbal medicine may containmore than one type of herb. These herbs, which contain a mixtureof naturally occurring substances, contrast with modernpharmaceutical drugs containing pure compounds.

In the past, it was not uncommon for healers to be womensince knowledge about plants and herbs were women’s teachings.These medicine women possessed knowledge about plants, herbs,and roots used in remedies such as teas. It is well documented thata substance in willow bark, originally employed by First Nationshealers, is now known by its chemical name, acetylsalicylic acid, a chemical compound commonly known as Aspirin®.

According to many Elders, the derivation of traditionalmedicines did not occur by accident or through trial and error.Some medicine women would go on a fast for several days duringwhich time they would meditate on the medicines and plants they would mix to create the desired effects. Certain families have spiritual understanding to mix medicines for heart disease,diabetes, hepatitis, and other illnesses. Today Elders areconcerned about the way traditional medicines might be exploited by some pharmaceutical companies.


Figure 4.27 The roots of bunchberrieshave been used by some First Nationspeoples as a cold remedy and thebark has been used as a laxative.



1. For each of the following substances, list four physical properties.

(a) water

(b) iron metal

(c) baking soda (sodium hydrogen carbonate)

2. What does a chemical property describeabout a substance?

3. Identify each of the following observationsas evidence of either a physical change or a chemical change.

(a) A piece of copper is heated until it melts.

(b) A silver spoon darkens when left in the air.

(c) Paper burns in a candle flame.

(d) A piece of plastic is stretched until it breaks.

(e) Table salt melts at 801°C.

CHECK and REFLECT4.2

4. From the following list, indicate whichitems would make good conductors.

(a) copper (b) Styrofoam™

(c) iron (d) woollen mitten

5. Identify each of the following as a statementthat describes either a physical property or a physical change.

(a) Ice melts.

(b) Hydrogen is a colourless gas.

(c) You chop a carrot.

(d) Copper wires bend easily.

(e) The ruby slippers are red.

6. What is an advantage and a disadvantageto the environment of making corn-basedproducts?

7. Compare traditional medicine used by First Nations and Métis peoples andmodern pharmaceutical drugs.

B5

Polyethylene Plastic

Polyethylene plastic is flexible, heat resistant, and strong. Children play with polyethylene toys,athletes drink from polyethylene bottles, and policeofficers wear polyethylene vests. Unlike some othertypes of plastic, polyethylene is considered safe to use in food containers.

What happens to polyethylene products whenwe no longer need them? If they cannot be re-used,another option is to recycle them. Some types ofpolyethylene plastics break down more easily when exposed to sunlight. These types of plasticsare considered photodegradable. However, theprocess takes a long time and releases tiny pieces of polyethylene as solid waste.

Science, Technology, Society, and the Environment

1. Make a list of items you used today that aremade from polyethylene. Identify which itemsyou could live without and which are necessities.

2. Describe two ways you could help decrease theamount of polyethylene that goes into landfills.

3. Is the process of photodegradable plastic decay a physical or chemical change? Support your response.

4. What are some possible benefits of using photo -degradable polyethylene to make disposablefood containers or shopping bags? What aresome possible problems with this type of plastic?



B6 Inquiry Activity

You can use a chemical reaction to change onesubstance into another substance that has differentphysical and chemical properties. You can also useheat energy to change the properties of substances.

Initiating and PlanningWhat are some characteristics of physical changesand chemical changes?

Investigating Physical and Chemical Changes

SKILLS YOU WILL USE■ Observing and measuring■ Drawing conclusions

CAUTION: Copper(II) sulphate is poisonous and canstain your clothes and skin. Keep your hair tied backwhen working near open flames.

• three scoopulas

• sodium carbonatepowder

• 250-mL beaker

• medicine dropper

• 0.5 M hydrochloricacid

• individual aluminummuffin tin

• white table sugar

• candle

• candle holder

• matches

• tongs or woodenclothespin

• three test tubes

• 0.5 M solution ofcopper(II) sulphate

• 0.5 M solution ofsodium carbonate

• two 5-mL measuringspoons

• test-tube rack

• copper(II) sulphate(solid)

• water

• stirring rod

Materials & Equipment

Toolkits 1, 2

Performing and Recording1. Copy Table 4.3 into your notebook. Be sure to

leave a row for each test.

Test 1 — Sodium carbonate andhydrochloric acid2. Using a scoopula, add a small amount (the

size of a pea) of sodium carbonate powder to abeaker. In your observation table, describe theappearance of the sodium carbonate powder.

3. Observe the hydrochloric acid, and record whatyou see in your observation table.

4. Write a statement about the kinds of evidence for physical or chemical change that you will look for when you add the hydrochloric acid to the sodium carbonate powder.

5. Using a clean medicine dropper, add five to eight drops of hydrochloric acid to the sodiumcarbonate powder. Record your observations.

Test 2 — Sugar and heat6. Obtain an aluminum muffin tin. Use a clean

scoopula to put a small amount of sugar (the sizeof a pea) in the centre of the aluminum muffintin. Record your observations of the sugar.

7. Suggest possible ways that the sugar mightchange with heating.

8. Place the candle securely in a candle holder, and then light the candle.

9. Using tongs or a wooden clothespin, hold thealuminum muffin tin over the candle’s flame.Slowly move the muffin tin back and forth over theflame to heat the sugar. Record your observations.

10. Place the aluminum muffin tin in a safe place to cool.

Observations

Test Before Change During Change After Change

Sodium carbonate and hydrochloric acid

Table 4.3 Observations of Physical and Chemical Changes


143Chapter 4 People of all cultures investigate matter according to various properties.©P

B6 Inquiry Activity (continued)

Test 3 — Copper(II) sulphate and sodium carbonate11. Using a measuring spoon, add 5 mL of

copper(II) sulphate solution to a clean test tube.Using a different measuring spoon, add 5 mL ofsodium carbonate solution to another test tube.In your observation table, describe theappearance of each solution.

12. Write a suggestion about what you think willhappen when the solutions are combined.

13. Combine the solutions, and record yourobservations.

14. Dispose of the solutions as directed by your teacher.

Test 4 — Copper(II) sulphate and water15. Using a scoopula, add a small amount (the size

of a pea) of solid copper(II) sulphate to a cleantest tube. In your observation table, describe the appearance of the substance.

16. Write a suggestion about what you think will happen when you add water to the copper(II) sulphate.

17. Fill the test tube two-thirds full of water and recordyour observations (Figure 4.28). Use a stirringrod to mix the water and copper(II) sulphate, and record any additional observations.

18. Clean up your work area. Follow your teacher’sinstructions to safely dispose of all materialsused. Wash your hands thoroughly.

Analyzing and Interpreting19. Which of the changes that you observed

appeared to be

(a) physical?

(b) chemical?

20. What evidence supports each of your answersabove?

21. Identify two physical and two chemical propertiesfor each of the following substances:

(a) sodium carbonate

(b) white table sugar

(c) copper(II) sulphate

Communication and Teamwork22. Create a flow chart that a classmate could follow in

order to identify physical and chemical changes.

Figure 4.28 Adding water to copper(II) sulphate



B7

Elements, compounds, and mixtures are part ofeveryday life. From the kitchen to the chemistry lab, we make use of different substances for theirdifferent properties.

QuestionHow can you use chemical and physical properties todistinguish among common substances (Figure 4.29)?

Properties of Common Substances

SKILLS YOU WILL USE� Carrying out a plan� Recording results

Toolkits 1, 2Inquire on Your Own

Design and Conduct Your Investigation1. Choose at least three substances to investigate.

They may be substances from your chemistry lab or from home.

2. Decide which properties you will investigate.Select some from the list below, or add others.

• colour and lustre

• combustibility

• conductivity

• density

• hardness

• melting point

• solubility

• texture

• reaction with acid

• reaction with water

3. Have your teacher approve your list of testsubstances and the properties you wish to investigate.

4. Think about these questions as you plan your procedure:

(a) How will you observe different properties, and what materials and equipment will you need to make these observations (Figure 4.30)?

(b) How will you record your results?

(c) How will you organize and present your results?

5. Write up your procedure. Show it to your teacherfor approval before carrying it out.

6. Carry out your procedure, and collect yourobservations.

7. Present your results in a poster or in another format suggested by your teacher.

Figure 4.29 Common substances

Figure 4.30 Possible materials and equipment

CAUTION: Keep your hair tied back when working nearopen flames. Take note of safety precautions for thesubstances you will be working with.

04_sk_sci9_se_ch04:Layout 1 3/26/11 2:50 PM 4

Meet Fadiah Parsons, a fine baking designer from Torquay, Saskatchewan.She has been baking specialty cakes, cookies, and desserts for 15 years and has gained wide acclaim for her work. Some of Fadiah’s work has beenfeatured in magazines. Many people have described her baked goods as“edible works of art” because of their striking appearance (Figure 4.31). But there is more to a great cake than simply appearance. Can you imagine constructing a cake standing nearly 1 m tall? And even if you could do that, how long do you think it would stand before falling over? “It is all in the ingredients,” Fadiah says.

Most people are familiar with the common angel food cake and its light,fluffy texture. But one must consider the facts that it is usually only about 10 cm tall and lasts for only a day or two. Most of these cakes use only theegg whites, which is why they are light and fluffy. Angel food cakes, however,could never stand up to 1 m tall because the same properties that makethem light and fluffy also make them unstable in structure. The cakesconstructed by Fadiah use plenty of whole eggs, whole milk, and a lot ofsugar. “Sugar gives body and is also a preservative. Without it, the cakeswould be soggier, denser, and would not last as long,” states Mrs. Parsons.

The cakes themselves are tasty, but it isthe fondant icing that makes them special.The skill is in adding the liquids (glucose,glycerine, gelatin, shortening, and water) to the icing sugar when mixing the fondanticing, and then adding just enough icingsugar to adjust the stiffness without makingit too sticky. Fondant icing is kneaded,unlike a poured icing that is heated into aliquid and then poured. A poured icingwould be fine for small, light cakes and petitfours, but would never work on tall cakessince it would simply flow to the bottom ofthe cake before it hardened. The fondanticing makes the cake firm in structure andalso allows Fadiah to become an artist.

Figure 4.31 Fadiah Parsons’ “edible works of art”

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Fadiah Parsons: Fine Baking Designer

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