Pure Substances and Mixtures webquest

Background Information

Physical Properties of Matter or Physical Changes

These are properties that do not involve the formation of a new substance; i.e., colour, odour, lustre, texture, boiling point, melting point, hardness, shape.

Chemical Properties of Matter or Chemical Changes

Involve the formation of a new substance with new characteristics. It describes how a substance reacts with other substances.

• e.g., sodium - a silver metal, highly reactive in water reacts with chlorine - a poisonous green gas to form sodium chloride (table salt) an edible compound that is necessary for our life processes.

A qualitative observation is vague and non-scientific. It cannot be precisely reproduced. Colour is a common qualitative indicator but, is red always red? Red can, in fact, describe a variety of shades. Look around the room at all the red items. Are they all exactly the same colour? You might describe some as being paler while others are darker.

Other words that convey a similar meaning are: weak vs. strong or diluted vs concentrated.

A quantitative observation involves numbers. It can be exactly reproduced. Examples of quantitative descriptions of solutions are:

- number of grams solute per 100 mL solvent (1 gram sugar per 100 mL water)

- number of mL solute per 100 mL solvent (2 mL milk per 100 mL coffee)

States of Matter

Comparing Solid, Liquid and Gaseous States

Changes of State

The Particle Theory of Matter

1. All matter is made up of small particles or atoms.

2. All particles of the same substance are identical; e.g., a particle of ice, a particle of liquid water and a particle of water vapour are all the same. They are just in different states.

3. The particles in matter attract one another. These “attractive forces” get stronger as particles get closer together. They are strongest in solid matter as these particles are closest together and weakest in gases where the particles are farthest apart. As temperature increases, the attractive forces become weaker and as temperature decreases, the attractive forces increase.

4. The spaces between the particles are large compared to the size of the particles themselves. The space is smallest in solids and largest in a gas. As temperature increases, the space between the particles increases.

5. The particles of matter are always in motion. Solids particles move the slowest and gas particles move the fastest. As temperature increases, the speed of the particles increases. As temperature decreases, the speed of the particles decreases.

Matter is organized according to a classification system. This system does not sort out matter according to its state or appearance. It uses composition instead. The composition of a substance depends upon the kind of particle of which it is made. The chart below, shows the classification of matter.

Elements

They are homogeneous and contain identical atoms. An element is matter that can no longer be divided or broken down into simplersubstances and still remain matter. Elements are the building blocks of matter. Examplesof elements are iron (Fe), sulfur (S), oxygen (O2), helium (He), neon (Ne), carbon (C), calcium (Ca).

Compounds

They are homogeneous and contain identical molecules. They are formed through chemical bonds. They can be broken down into simpler substances – either into new molecules or into elements. Compounds always combine in a fixed ratio by mass. Examples of compounds are carbon dioxide (CO2), ammonia (NH3), sodium chloride (NcCl), ethanol (CH3CH2OH), sugar (C12H22O11) and water (H2O).

Mixtures

Mixtures contain two or more pure substances that are not chemically combined. The pure substances can vary in their amount. When substances form a mixture, they do not chemically react. They maintain their chemical characteristics but their physical properties may change. For instance, when you dissolve drink crystals into water they retain their flavour.

Types of Mixtures

1. Mechanical Mixtures -They are heterogeneous (have two or more visible parts). The two different types of substances are easy to see and can be easily separated.

a) Mechanical mixtures - two solids mixed together; e.g., sand and rocks, wood chips and beads.

b) Suspensions - a solid and a liquid which mix but settle upon standing; e.g., silt and water.

c) Emulsions - two liquids, which mix but separate upon standing; e.g., oil and water. An emulsion can be permanently mixed by adding an emulsifying agent. Mayonnaise added to an oil and vinegar salad dressing will stay mixed.

2. Colloids - are homogeneous mixtures that are made of particles of one substance suspended into another. The suspended particles get stuck in the spaces of the other particles. This allows them to scatter light. Colloids will show the Tyndall Effect.

Examples of colloids are: butter, mayonnaise, steam, clouds, fog, egg white, paint, smoke, whipped cream, shaving cream, gel, hair mousse, homogenized milk.

Tyndall Effect - Some mixtures that appear to be solutions may prove not to be solutions after all. If the path of a bright light shining through a mixture can easily be seen, then that mixture is not a solution. A non-solution contains particles large enough to scatter or reflect light, showing the path of light as it passes through the mixture. This scattering of light is called the Tyndall Effect. True solutions do not show the Tyndall Effect. 

*** entire webquest was copied from http://mrmcclung.ca/Grade%207%20Portal/index7.htm  and placed into a separate webpage for ease of access for students. Content is not original, nor has it been created by Ms. Carniel.

Task 1

There are many ways of separating the components of mixtures. These techniques include:

1. Evaporation

2. Sifting

3. Filtration

4. Distillation

5. Magnetism

Modern industries use these techniques everyday. Evaporation is used in the production of maple syrup. Different sizes sieves are use to separate wheat grains in the production of white bread. Water purification plants use a variety of filters. Drinking water can be separated from salty sea water by distillation. Recycling plants use magnets to separate metal from glass.

In Task 1, we'll explore the process of filtration and how it works to separate unwanted components of mixtures from those that we can use.

Task 2

Scientists around the world are trying to learn more about the vast amounts of chemicals that are dumped or washed into our rivers, lakes and oceans. There are many questions they must find answers to. For example, many chemicals are dangerous only when they reach a certain concentration. What is the dangerous concentration for each chemical? Where do the chemicals come from? How can we reduce the amounts of the dangerous chemicals that enter our rivers, lakes and oceans?

This research, along with increasing public awareness, is resulting in a reduction in the amount of waste being dumped into some water systems. Many countries are aware of the effect of pollution on our clean drinking water and have regulations in place to ensure the safe use and disposal of toxic pollution.

There are many ways that human activities pollute water. There are also many ways that we can prevent water pollution, not just for ourselves but also for the many other life forms that require clean water to live.

Task 3

You have acquired tons of knowledge over the past weeks... now's the time to show it! Get together with your partners, choose a subject, do the research, build what it takes. But remember... you won't have a lot of time...

Process

Task 1

Filtration

To get ready for our webquest tasks in this unit, we're going to do the following experiment in class....

Problem

To filter a variety of mixtures and observe the results.

Materials

Method

1. Prepare the filters, filter papers and collection beakers.

2. Label the collection beakers A, B, C, D & E.

3. Obtain the four solutions from the instructor.

4. Using safe lab technique filter each solution, collecting the filtrate in the labelled beakers.

5. Use the filtrates collected to complete the Observation chart.

Observations

Record your observations on the chart.

Analysis

1. Which of the mixtures were solutions? Which were mechanical mixtures?

2. What happens if you filter a mechanical mixture?

3. What happens when you filter a solution?

Application

Give two examples of filters that you use at home.

Follow-up

Now that you have learned how to separate components through the process of filtration, put your knowledge to work. Using the materials that have been assembled in the classroom, you and your class have the task of building a hand-held filtration device.

The only difference is: Instead of a desert island, your filter has to produce clean drinking water from water found in ponds. Will you be willing to drink the water that your filter makes?

Task 2

Alberta's Oil Sands

The argument for -

Alberta's Oil Sands Canada’s energy future lies in the oil sands. Our country possesses approximately 175 billion barrels of oil that can be recovered with today’s technology. Of that number, 170 billion are located in the oil sands.

The industry understands that Canadians are concerned about the impacts of our work, and expect that industry will manage the resource responsibly.

The argument against -

• The world's dependency on fossil fuels will never be solved unless dangerous and potentially devastating projects like the Oil Sands are closed

• The project has already ruined the ecology in a area approximately the size of England

• The lives of thousands of native Canadians in the area have been forever disrupted

• Wildlife and diverse plant life will never return to an area so changed through oil development.

You and your partner will have two class periods plus time at home to research both sides of the argument, the issues surrounding the the development of the oil sands and related issues. On the third day, you will be expected to effectively debate the following resolution -Assignment

"The Alberta Oil Sands project is an essential and safe way to ensure Canada's energy future."

All research will be submitted on the day of the debate, fully cited using the MLA citation system. See the "evaluation" section of this site to learn more.

Task 3

Problem (Final Project)

Select ONE of the following topics to complete as a group project. You will be allowed access to the school library and computer facilities to do your research. You are also expected to work on this project during your homework time. Although this is a group project, each student will be graded separately, based on their contributions to their group.

The Project is to be presented as one of the following:

- a poster                            - a research report                                - a video

  - a scale or full-size model       - a BitStrip.. or anything else you can think of!

Each project must contain the following -

• all research notes collected by the group

• a full written component discussing your problem and solution. The length of the report will depend on the subject chosen and research completed

• a detailed description of what task was done by which members

• some type of visual presentation - something that can be put on the class website

Suggested Topics

These are just a few ideas.... have another one? Let's talk about it! If there is a subject or problem that is relevant to what we have been learning about and you'd like to research a solution, I want to hear about it!

Evaluation

Assessment Rubric - Filtration System

Observation Sheet - Town Hall Meeting, Great Lakes Pollution

Assessment Rubric - Final Project

Glossary

atom - particles which cannot be broken down during normal physical or chemical changes. Also called an element.

boiling - the change of state when a liquid turns into a vapour.

colloid - particles of one substance that are suspended in another molecule.

compound - a substance that can be broken down into two or more simpler substances by means of a chemical change. It is made up of identical molecules.

concentrated - a solution that contains a large amount of solute in a solvent. A strong solution.

condensation - the change of state from the vapour phase to the liquid state.

density - mass per unit volume.

dilute - a weak solution.

dissolve - to go into solution.

distillation - process of evaporating a liquid to a gas and then condensing it back into a liquid to purify a substance or to separate two substances.

element - see atom.

emulsion - a mixture of two liquids that do not remain mixed. e.g., oil and water.

filter - paper or other substance that is used to separate the particles in a mixture.

filtrate - the liquid once it has passed through the filter during filtration.

heterogeneous - more than one substance is visible in the mixture.

homogenous - only one substance is visible in the mixture.

hypothesis - a tentative explanation put forward to explain certain observations. An educated guess.

insoluble- will not dissolve.ade 7

ion - an atom or molecule that has lost or gained electrons thereby carrying either a positive or negative charge.

mass - the measure of the amount of matter in an object.

mass concentration - the number of grams of solute in a 100 g of solvent.

matter - anything that has mass and takes up space.

mechanical mixture - two or more substances that have been combined and in most cases they can be separated.

melting - the change of state where a solid turns into a liquid.

mixtures - a group of matter that includes solutions, suspensions, colloids, emulsions and mechanical mixtures.

molecule - two or more atoms joined together in a fixed ratio by mass and which have unique physical and chemical properties.

plasma - a phase of matter in which an electrically neutral gas contains positive ions and electrons. The surface of the Sun is believed to be in the plasma state.

potable - drinkable.

pure substance - homogeneous matter with each particle identical.

residue - the particles that are trapped in the filter during filtration.

saturated - to completely dissolve the greatest amount of solute possible in a fixed amount of solvent at a given temperature.

solidification - the change of state where a liquid becomes a solid.

soluble - will dissolve.

solute - a substance that is dissolved in a solvent.

solution - a mixture that is evenly mixed and is made up of a solute (is dissolved) and a solvent (does the dissolving).

solvent - substance that does the dissolving.

states of matter - all matter exists as either a solid, liquid gas or plasma, depending on the temperature.

sublimation - the change of state where a solid passes directly to the gaseous state (or vice-versa).

supersaturated - to add more solute to a solvent than can be dissolved at the given temperature.

suspension - a mixture of a solid and a liquid that can be separated through filtration and settle when mixed.

unsaturated - more solute can still be dissolved in the solvent at the given temperature.

volume - the space that matter occupies.

WHMIS - Workplace Hazardous Materials Information and Safety.

*** entire webquest was copied from http://mrmcclung.ca/Grade%207%20Portal/index7.htm  and placed into a separate webpage for ease of access for students. Content is not original, nor has it been created by Ms. Carniel.