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UNIT 2 – MATTER AND CHEMICAL CHANGE

UNIT 2 – MATTER AND CHEMICAL CHANGE. TOPIC 1 – EXPLORING MATTER. Learning target: The students will describe and apply different ways of classifying materials based on their composition and their properties (pure substances and mixtures). Chemistry is the:. The study of matter.

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UNIT 2 – MATTER AND CHEMICAL CHANGE

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  1. UNIT 2 – MATTER AND CHEMICAL CHANGE TOPIC 1 – EXPLORING MATTER Learning target: The students will describe and apply different ways of classifying materials based on their composition and their properties (pure substances and mixtures).

  2. Chemistry is the: • The study of matter • Theproperties (differences) between matter • Changesin matter (reactions)

  3. But what is matter? • Matter is anything that: Has mass Takes up space What exists on Earth but is not matter? Energy!!

  4. All chemicals need to be treated with care. • Many chemical are CAUSTIC and will, burn, corrode, or destroy organic tissue. Eg. Acids, strong bases, and other chemicals easily break down skin and muscle and can cause permanent damage.

  5. Classifying Matter Matter is most often described using the Particle Model of Matter • All matter is made up of tiny particles. Eg. In one drop of water there are 1 700 000 000 000 000 000 000 water particles in it! (that’s 17 with 20 zero’s behind it) The number of particles in the human body is approximately equal to the number of peas it would take to cover 250 000 Earths to a dept of 1.5 meters! If every person on the planet counted continuously from birth to death and we added these numbers together, that would be about how many atoms that make up the head of a pin!

  6. 2. Each pure substance has its own kind of particles that are unique. The particles of one type are all identical to each other and are different from other particles of other pure substance. Eg. All salt particles taste salty. All sugar particles taste sweet. All water particles have the same melting (0 0c) and boiling point (100 0c).

  7. 3. Particles attract each other. Objects with stronger attraction between their particles are solids. Objects that have weak attraction between particles are gases. 4. Particles are always moving. Vibrating, rotating , bumping into each other. 5. As the temperature increases, the particles move faster (expand). If the temperature decreases, the particles move slower (contract). Faster moving particles take up more space as they bump into each other causing the object to expand. As the temperature decreases, the particles get tighter together and the object contracts.

  8. The particle model helps to explain the 3 states of matter:

  9. Matter can be further classified according to its composition. Matter Solid, Liquid, or Gas Pure Substances Mixtures • Only one type of particle • Two or more types of particles mixed together • Have set properties (values DO NOT change) • Values of properties change depending on how much of each particles is present in the mixture Eg. Water (H2O) – always boils at 100oc Eg . Salt (NaCl) – always boils at 1465oc Eg. Salt Water – boiling point varies depending on the amount of salt in the solution (the more salt, the higher the boiling point)

  10. Mixtures can further be broken down: • Mixtures HETEROGENEOUS (Mechanical Mixtures) HOMOGENEOUS (Solutions) -particles are evenly mixed so it looks like ONE substance (uniformly mixed) -have varying sizes of particles in the mixture (can be seen) • -can be further classified as: • Ordinary Mech. Mix. • Suspensions • Colloids -clear (can be colored) and will not filter out -light passes through evenly Eg. Sugar water

  11. Heterogeneous Mixtures HETEROGENEOUS (Mechanical Mixtures) Ordinary Mech. Mix. Suspensions Colloids -can see the different parts -looks like one substance but the two parts will separate out over time -small particles of one substance suspended in another -parts stay mixed Eg. cookie dough gravel, cement -CAN be filtered and WILL scatter light -WILL scatter light Eg. Hair Gel, Fog (Water vapour and air) Eg. Dust and water

  12. Colloid -light is scattered by the particles in the liquid Solution -light easily passes though

  13. Colloids Emulsions -a liquid that is mixed in with another liquid Eg. Milk, jelly, and salad dressing PROBLEM: may quickly separate to form layer of the original liquids. That is why we use emulsifying agents.

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