January – March 2009

- What is chemistry? - Who studies chemistry? - What is a mixture? - What is a solution? - What do you hope to learn in this unit?

Task : Find the differences between these pairs:  Glass & Steel  Water & Milk  Gasoline & Oil

 Resemblances : › Solid › Construction materials › Can be melted › Cannot bend in original state (without being melted)  Differences : › Color (glass is transparent, steel is grey) › Weight (steel is heavier, if the size is the same) › Steel (metal) can conduct electricity › Glass is fragile, steel is not easily broken

:  Resemblances : › Liquid  They can freeze and evaporate › We can drink them › Good for our health › Nonflammable (cannot catch fire)  Differences : › Color (water is clear, milk has color) › Water is transparent, milk is not › Water is more widespread on earth (2/3) › Water is naturally on Earth, milk comes from cows › Milk is thicker than water

 Resemblances : › Liquid › Transparent › Combustible (can catch on fire) › Mixture (not pure substances)  Differences : › Color (oil has color, gasoline is clear) › Smell › Oil is thicker than gasoline › Gasoline is what we put in our cars › Cooking oil can be used in a kitchen

Module 2 : Pure Substances and Mixtures

4.1 - Matter in Your World  Matter: any material that occupies space and has a mass (includes all solids, liquids, and gases).  Properties: the characteristics that are used to describe matter. Examples: size, shape, form, state, smell, color, taste,.  *Every material has its own set of properties.

Example  Water at the beach (photo on page 98) has the following properties: Clear, liquid colorless odorless Freezes at 0º C * (under normal conditions) Boils at 100º C

 Some materials cannot be described by a single set of properties.  Mixture: a material that has more than one set of properties. It contains more than one kind of matter combined in such a way that it keeps its own set of properties.  Two or more substances combined together is a mixture.

 Heterogeneous: means made up of parts, or mixed. A heterogeneous mixture is made up of parts that can be seen and observed.

 Homogeneous mixture : means every part of the material is the same. There is only one set of properties.  Examples: water, air

Heterogeneous or Homogeneous? What do you think? 1. Water with salt in it 2. Apple juice 3. Peanut butter 4. Salt and pepper mixed together 5. Smoothie 6. Orange juice with pulp 7. Pure water

A Classified Photograph- Activity (p. 101) Study the photograph on p Make a table (like the one on p. 101) 2. Find 10 substances in the image. 3. Classify whether each material is heterogeneous or homogeneous. Record your decision in the second column of your table. 4. In the third column, identify what made you decide (observations).

Quiz 4.1  The quiz on section 4.1 : 5 definitions (matter, properties, homogeneous, heterogeneous, mixture) Examples

Study time!!  Study your 5 definitions (matter, properties, mixture, homogeneous, heterogeneous) Write them down! Study with a partner (no laptops)  Make a list of as many properties as you can think of.

4.2 – What is a mixture?  Anything with at least two distinct sets of properties (characteristics) is a mixture of at least 2 materials.  Examples: sand, pop, sandwich (All are heterogeneous.)  When a mixture’s different parts can be identified this easily, the mixture is usually called a mechanical mixture.

 Even so-called “homogenized” milk turned out to be a heterogeneous mixture.  It looks homogeneous. With your eyes only, you cannot detect bubbles or bits with a different set of properties.  With a microscope, the milk contains many tiny elements of a second liquid – fat. No matter how smooth milk appears, it is actually a heterogeneous mixture.

By now you may be wondering …  Is anything homogeneous?  Is everything heterogeneous?  Isn’t anything pure?  Is everything on Earth really a mixture?  Can a mixture be homogeneous?

Homogeneous Mixtures  A homogeneous mixture is called a solution.  Solutions are everywhere. 2/3 of Earth is covered with a liquid solution - the water of the oceans.  Earth is surrounded by a gas solution that we call air – a homogeneous mixture of oxygen, nitrogen, and other gases.

Homogeneous Mixtures  There are even solid solutions, such as a sterling silver. (Sterling silver is a solution of silver and copper.)

What to do now… 1. Sciencepower p Do the activity in the yellow square “Homogeneous Mixtures”. 2. Answer questions 1 of “What to do”. When you are done, complete # 2, 3, In Sciencepower p. 111 complete # 1 and # 2 a). We will correct in a few minutes.

Answers #1. How may sets of properties do you need to observe in order to classify a material as a heterogeneous mixture? -Anything with two or more distinct sets of properties. 2. a) What is a solution? -A homogeneous mixture is a solution.

4.3 – Mixtures and Pure Substances  We have seen that heterogeneous mixtures have two sets of properties.  There are also homogeneous mixtures, which have properties that are a blend.  The blend of properties depends on how much of one material and how much of the other material are in the mixture.

 Are there any pure substances – materials whose properties are not a blend and are always the same? √ Yes there are pure substances. Examples: gold, oxygen, copper, aluminum, silver, sugar, salt, etc.

How can you find a pure substance? 1. First you look to see if the material is homogeneous. A pure substance must be homogeneous. 2. Investigate (observe) the properties of the material to find out if they are always the same.

3. If they re all exactly the same in all parts of the material, no matter what part of the world the material comes from, then you may conclude that you have a pure substance. 4. A thorough investigation is necessary before anything can be classified as a pure substance.

What we have seen so far about matter All materials Heterogeneous materials Homogeneous materials Homogeneous mixtures Pure substances

A Theory  How can pure substances always be the same?  How can solutions have blended properties but still be homogeneous?  To answer these questions, scientists need a theory (explanation).

 The theory that scientists use to explain the properties of various mixtures and substances is called the particle theory of matter. 1. All matter is made up of extremely tiny particles. 2. Each pure substance has its own kind of particle, different from the particles of other pure substance.

 Based on the particle theory, a pure substance is a material made up of only one kind of extremely small particle.  According to the particle theory, all water particles are exactly the same.  Pure water, no matter how or where it is obtained, always contains identical particles.

 Similarly, all particles of table sugar are exactly the same.  They are different from water particles, different from the particles of any other substance.  But all the particles of table sugar are the same.

Lets see how well you understood… 1. Turn to p. 115 in Sciencepower. 2. Answer to questions #1. a, b, c and #2. a, b, c, d. 3. In Sciencepower p. 118 # 6 4. We will correct the exercise together in minutes.

Answers « Pouring? Shaping? Filling? (p. 115) 1. Name the state(s) in which a material: a) has a fixed shape? A - solid b) takes the shape of its container B - liquid c) always fills watever container it is in C - gas

2. Name the state(s) in which the particles are: a) far apart from each other C – gas b) relatively close together B - liquid c) free to move around C - gas & B - liquid d) held in fixed positions A- solid

Date 1. Introduction – Chapter 5 2. Section 5.1 definition - dissolution 3. Comic strip