Science 24 Tutorial #1 – Sept. 9th
Welcome to our first tutorial.
Attendance at tutorials is mandatory and will be included in your mark. Please keep in
mind that signing in for the tutorial is not enough in itself. You are expected to be an
active participant.
How many of you have already attended at least one vClass tutorial?
Discuss general features – raise hand, check mark/x, private messages (I can see them).
Every Thursday at 10am, I will hold a help session. You do not have to attend the help
sessions, but are encouraged to do so if you have any questions or if you are having
difficulty with any of the content that we are covering.
We will be covering four units this semester. There will be a test at the end of each unit.
Although there is not a final exam in this course, you will be expected to attend a lab
session in December.
Our first unit is called Applications of Matter and Chemical Change. In this unit, you
will learn about how everyday life depends upon technological products and processes
that produce useful materials and energy and analyze their potential effects on the
environment. We will also look at chemical reactions.
We’ll begin today by looking at how technology has changed the products available to
us. 100 years ago, products that you would have seen include unprocessed cheese, beef
jerky, eggs, or materials like tent canvas, raw cotton or sheep skin, and leather shoes or
boots. What are some items that have just been developed in recent history?
Ans. Processed cheese slices, any food containing additives or preservatives to keep it
fresh, a nylon tent, clothing made from synthetic fabrics such as polar fleece (made from
recycled plastic), or shoes made from plastic or another synthetic material.
What are some of the similarities and what are some of the differences? Chart.
Please turn to page 4 in your text, and let’s look at some of the getting ready questions
together. (Go through these and discuss them).
Did you know that the creation of ice cream was somewhat of a scientific discovery in
the 1600s? (Read section from manual). Does anyone know what the secret is to
icecream freezing? What is added? Ans. Salt. Salt lowers the temperature below the
freezing point of the ice-cream mixture. Lowering the temperature slows the particles of
the ice-cream mixture to the point where they will change state. In other words, the
mixture will change from a liquid state to a solid state.
Chemistry surrounds our daily lives. Like all scientists, chemists try to describe and
explain the world. Chemists start by asking questions such as:
How can I protect my crops from insect pests?
How can I get stains out of clothing?
How can I waterproof a jacket or a pair of boots?
To answer these questions, chemists develop models, conduct investigations, and seek
patterns. They observe various types of chemical reactions, and they perform
calculations based on known data. They build continuously on the work and discoveries
of other scientists.
What knowledge of chemistry helps farmers?
Ans. Pesticides – used instead of pulling weeds and killing insects.
What are the two types of pesticides called?
Ans. Herbicides to kill unwanted plants, and insecticides to kill unwanted insects.
Read the “Did you Know” box on page 6.
There are some potential hazardous aspects of modern-day chemistry. Reports on many
agricultural and other chemicals have shown that the effects on the human brain and
central nervous system can include headaches, blurred vision, muscle weakness, and
memory problems. Also, the effects may be more hazardous to children, since they
appear more vulnerable to such chemicals.
How has the art of making soap changed?
Ans. Manufacturers have replaced some or all of the animal fat with plant oils.
Read:
The soap molecule consists of a long strand with a water-loving, grease-repelling group
on one end. It has a grease-loving, water-repelling group on the other end of the
molecule. If you add a drop of soap into clean water, all of its molecules gather on the
surface with their water-loving ends stuck in the water and their fat-loving ends waving
in the air.
Slide a greasy dish into the water and the fat-loving end of each molecule sticks to
the grease. As the dish sinks, it takes the soap molecules with it because the grease-loving
head ends are attached to the grease. Their water-loving tails are still waving in the water
like microscopic tadpoles. The end result is a small blob of grease completely surrounded
by a layer of soap molecules — all with their grease-loving heads pointing into the grease
and their water-loving tails pointing outwards into the water. These small blobs can be
rinsed away leaving the dish shiny and clean.
The fact that soap has grease-loving (hydrophobic) and water-loving (hydrophilic)
ends is true of all types of soap.
What is a synthetic product?
Ans. Man-made. Natural fibres come from plants and animals. Synthetic fibres are the
products of complex chemical reactions.
What are some examples of synthetic materials?
Ans. Nylon, polyester etc. (Look at fig. 1.2 on page 8…what would some of the
benefits be to using the synthetic materials vs. the natural ones)
What is a polymer?
Ans. The word “polymer” comes from the Greek words poly (many) and meros (parts).
A polymer is a giant molecule made up of many small and identical sub-molecules.
Polymers can be natural or synthetic. Examples of natural polymers include cellulose (if
you have ever had a piece of celery stuck between your teeth, you are familiar with this
plant polymer). Or silk produced by silk worms.
Polymers can be made synthetically by scientists with physical characteristics designed to
meet a particular need. (Refer to table1.1 on page 9 to see some examples).
What is an alloy?
Ans.
Metals and Alloys — Pure metals are elements that can be identified on the periodic
table. These elements are on the left side (left of the staircase) of the periodic table.
Examples of pure metals include copper (Cu(s)), used in electrical wires, and aluminum
(Al(s)), used in cooking foil and soft-drink cans.
(Turn to the back of the text and look at the periodic table) In your assignment you
needed to identify the chemical symbol for some elements. (Do a couple of examples
with the class)
Metal alloys contain more than one metallic element. Metal alloys have properties
that are different from the properties of the individual metal elements that make them up.
Adding other metals can affect the density, strength, electrical conductivity, and
environmental degradation of the alloy. For example, adding a small amount of iron to
aluminum will make it stronger.
Two common examples of metal alloys are stainless steel and the gold used to
make jewellery.
• Stainless steel is an alloy of iron, nickel, chromium, and carbon.
• The gold used in jewellery is an alloy of gold and another metal such as silver, copper,
nickel, or zinc.
Adding some chromium metal to steel will slow the rusting process, but will make
the alloy more brittle. Bronze may be a familiar substance to some students. This alloy is
made of tin and copper. Because of its hardness, bronze has been used for thousands of
years in weapons, utensils, and art objects.
Read over some of the answers from U1L1 part c, part 1 on jewellery. (From the web
site that would not work).
In science 14, you learned about hazardous household product symbols and the
workplace hazardous materials information system. Can somebody tell me what these
are?
Ans. HHPS are located on containers to warn you of any dangers in handling products in
your home. Refer to page 12 to see the symbols.
From hair spray to bleach to household cleansers, it is essential to know the dangers
posed by improper use and storage of hazardous products, and to treat them with caution.
Most common household cleaners contain acids or bases. Acidic cleaners, such as toilet
bowl cleaners, often contain hydrochloric acid or sodium bisulfate to remove alkaline
deposits or stains. Basic cleaners, such as drain cleaners, are designed to dissolve grease,
hair, and food. They often contain sodium hydroxide and sodium hypochlorite (bleach)
WHMIS symbols are designed for the workplace. Why are they necessary?
Ans. There are many chemicals in the workplace.
WHMIS has labels and an MSDS with further info about the chemical. (See page 19)
I’d like everyone to choose a workplace now and see if you can identify five hazardous
substances you would find in each one.
Eg. Hair salon, school, factory etc.
Automotice shop – Car batteries use a chemical change. The battery cells are filled with
sulphuric acid. This sulphuric acid reacts with the lead in a car battery to produce
electricity. Although you can recharge or “jump” a lead-acid battery, you need to be
careful when doing so. This chemical reaction produces hydrogen gas, which may
explode if ignited. You are probably familiar with the use of jumper cables to start a car
with a dead battery. The chemical reaction used to charge a battery produces hydrogen
gas that can explode if ignited.
Refer to the chemists recipe for ch. Chip cookies to see how products we use every day
are actually chemicals.
What are some other chemical reactions that you are surrounded by each day?
Ans. Washing dishes and clothing, brushing your teeth.
Often, gases are released as a result of a chemical reaction. There are tests that you can
do in the lab to determine what type of gas is produced. (Refer to the investigation on
pages 26 and 27)
(Give students time to read it)
Question: How can you test for carbon dioxide gas?
Ans. Limewater turns cloudy in the presence of carbon dioxide gas.
How can you test for hydrogen gas? Ans. Insert a burning splint into the test tube and if
the gas suddenly causes a squeal or pop, this indicates the presence of hydrogen gas.
How can you test for oxygen gas? Ans. Insert the glowing wooden splint into the test
tube. If the flame re-ignites, this indicates the presence of oxygen gas.
In a chemical reaction, does anyone know what the substances that you begin with are
called?
Ans. Reactants.
After the chemical reaction what are you left with?
Ans. Products.
Reactant 1 + reactant 2  product 1 + product 2
A reaction that you are familiar with is respiration (ie. reaction that occurs to convert the
food you eat into the energy your body can use). Can you list the reactants and the
products?
Oxygen + food (glucose)  carbon dioxide + water + energy
What are some indicators that a chemical reaction has occurred?
Ans. Gases may be given off
-new solids may be formed
-colour changes may occur
-release or absorption of energy
-odours given off.
Chemical reactions can either be exothermic or endothermic. Does anyone know the
difference?
Ans. exothermic – this means that energy is being released into its surroundings. Eg.
Gas being burned in a car.
Endothermic – Chemical reactions that absorb energy. Eg. Photosynthesis where a plant
absorbs light.
Types of Reactions
Combustion – A reaction when fuel burns in oxygen to produce carbon dioxide and
water vapour.
Fuel + oxygen  carbon dioxide + water vapour + energy
Eg. Barbecues use propane
Propane C3H8(l) + oxygen O2(g)- carbon dioxide (CO2) and water vapour (H2O)
Eg. Vehicles use ethanol
Ethanol C2H5OH (l) + oxygen gas (O2)  carbon dioxide (CO2) and water vapour
(H2O) (g)
Neutralization – an acid is added to a base to produce a salt compound and water.
Acid + base  salt + water
(note – the “salt” is not necessarily NaCL(s) which is table salt.)
Simple Composition Reaction – Two or more elements combine to form a compound.
Whenever you see two elements as reactants, you know that the reaction is a simple
composition reaction. The product is always a compound. (an exothermic reaction)
Eg. Hydrogen gas + oxygen gas  water
Simple decomposition reaction – A reaction that breaks a compound into its component
elements is known as a simple decomposition reaction. Whenever you see a compound
as the only reactant, you know the reaction is a simple decomposition reaction.
(endothermic)
Eg. Hydrogen peroxide liquid (H2O2(l))  H2(g) + O2(g)