Understanding Matter and Energy Pure Substances and Mixtures Big Ideas 1. Matter can be classified according to its physical characteristics 2. The particle theory of matter helps to explain the physical characteristics of matter 3. Pure substances and mixtures have an impact on society and the environment 4. Understanding the characteristics of matter allows us to make informed choices about how we use it Science- Overall Expectations- Pure Substances and Mixtures 1. Evaluate the social and environmental impacts of the use and disposal of pure substances and mixtures 2. Investigate the properties and applications of pure substances and mixtures 3. Demonstrate an understanding of the properties of pure substances and mixtures, and describe these characteristics using the particle theory 1. Classifying Matter Matter: Anything that has mass and takes up space Matter can be classified by a) its physical state 1) Solids- definite shape and volume 2) Liquids- no definite shape but definite volume 3) Gases- no definite shape or volume Classifying Matter by Composition Matter can also be classified by what they are made of (composition) All matter is either A) A pure substance- made of only one type of matter B) A mixture- made up of two or more different substances Pure Substances and Mixtures Pure Substances Every part of the substances has the same composition Every part of the substance looks the same Uniform, or homogeneous Mixtures Mixtures can look the same throughout (pop) or can have visibly different parts (a pizza) Either way, each substance in the mixture keeps its properties Classifying Mixtures Mixtures can be grouped into two categories: Mechanical mixtures- they do not have the same appearance throughout (also called heterogeneous mixtures) Trail mix Solutions- have the same appearance throughout (one substance dissolves in another) homogeneous mixtures Sugar dissolving in tea Mechanical Mixture Solution 2. The Particle Theory of Matter Everything (whether we can see it or not) is made up of particles Particles are very small portions of matter The Particle Theory The particle theory of matter describes and explains the behaviour of solids, liquids, and gases There are 6 parts/steps to the particle theory The Particle Theory of Matter 1. All matter is made up of particles 2. All particles of one substance are identical 3. The particles of matter are in constant motion 4. Temperature affects the speed at which particles move 5. Particles have forces of attraction between them 6. There are spaces between particles Matter and Particles All particles of one substance are identical Particles of pure substances are identical, while the particles that make up mixtures are different Different substances are made up of different particles Particles in Motion All particles are always moving They vibrate constantly because they have kinetic energy- the energy of movement In solids, particles vibrate in one place In liquids, particles slide around and over each other In gases, the particles move around as far as the space they are in allows, completely filling the container Temperature, Heat, and Motion Temperature- the measure of the average kinetic energy of the particles in a substance (how hot a substance is) Heat- the energy that transfers from a substance at a higher temperature to one at a lower temperature When heat transfers from a hotter substance to a cooler one, the particles in the cooler substance start moving faster Space and Attraction between Particles There are spaces between particles There are forces of attraction between particles Solid particles are much closer together and have a greater attraction compared to liquid and gas particles Temperature and Changes of State Changes in temperature often lead to changes of state (a change from one physical state to another) All matter exists in solid, liquid, and gas forms Different substances maintain different states at different temperatures (e.g., at room temperature, water is a liquid, wax is a solid, and oxygen is a gas) Temperature and Changes of State 3. Solutions- Which cookie recipe do you think will taste better? 2 cups flour 1 tsb baking soda 1 tsb salt 1 cup butter 1.5 cups sugar 2 eggs 2 cups chocolate chips 2 cups flour 1 tsb baking soda 1 cup salt 1 cup butter 2 tbsp sugar 2 eggs 2 cups chocolate chips Solutions Even though the ingredients are exactly the same, the two recipes will taste VERY different. Why? Because the concentration of the recipes are different From last time. We learned that a solution is a homogeneous mixture (looks the same throughout) 3. Concentration and Solubility Solutions can appear as solids, liquids, or gases A solid solution is called an alloy Liquid and gas solutions are called solutions Solutes and Solvents Solutions have two main parts: A) A solute- the substance that dissolves B) A solvent- the substance that does the dissolving (or the substance in which the solute dissolves) Solvents Usually, you will have more of the solvent than the solute in the solution E.g., Salt water (the Ocean), Air (nitrogen is the solvent, oxygen, co2, etc. are solutes) The Universal Solvent Water is known as the universal solvent because there are so many different liquids, solids, and gases that dissolve in it to make solutions However, not everything will dissolve in water. Can you think of any substances that do not? What is this? Solubility Solubility is the ability of a solute to form a solution with a solvent The maximum amount of solute you can dissolve in a certain amount of solvent at a certain temperature When a substance does not dissolve in a solvent, that substance is insoluable Concentration Concentration is the amount of solute dissolved in a specific amount of solvent Can be expressed in qualitative terms Concentrated solution- solution that contains a large amount of dissolved solute and very little solvent Dilute solution- very little solute dissolved in the solvent Which one is concentrated? Which one is diluted? Concentration Concentration can also be explained in quantitative ways (using numbers) Example: if 5 g of salt are dissolved in 500 mL of water, the concentration of the solution is 5g/500 mL How can we simplify this? Saturation In any solution, there is a maximum amount of solute that a solvent can dissolve (at a specific temperature) When a solution reaches that maximum, it has reached its saturation point If the saturation point has not been reached, it is an unsaturated solution Supersaturated solution What do you think the term supersaturated means? Any idea how we could create a supersaturated solution??? 4. Factors Affecting Solubility Which one do you think will dissolve more quickly in water? The table salt will dissolve at a faster rate than rock salt Why? Solubility is affected by the properties of solute particles and how they interact with the properties of solvent particles Cleaning Oil and Water based paints Which one will dissolve fastest? Solubility and the Particle Theory We have learned that all matter is made up of particles All particles are in constant motion (rotating, vibrating, moving from place to place) With motion, solute particles free themselves from clumps of particles and individual particles are carried away by bumping into solvent particles. Other solvent particles then bump into and carry off other solute particles until all particles are evenly distributed throughout the solvent Rate of Dissolving How fast a solute dissolves in a solvent is variable The rate of dissolving is affected by three factors 1) Stirring 2) Temperature 3) Particle size Stirring Stirring a solution increases the rate at which a solute dissolves in a solvent When solutions are stirred more water (solvent) particles are free to bump into solute particles and surround them Temperature Particles move more rapidly at higher temperatures (think of the metal spoon), as heat is transferred by the movement of the particles When particles move faster, more solvent and solute particles bump into each other Particle Size Larger particles take longer to dissolve than smaller particles Particles of a solvent will contact solute particles at the surface of a clump or crystal of solute particles Large pieces of solute must be broken apart to come in contact with solvent particles