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Chapter 2

Chapter 2. Classifying Matter. Matter & Chemistry. Matte r - is all the material you can hold or touch Everything around us Chemistry – is the study of change in matter Elements, Compounds, Mixtures. Atoms & Elements. Atoms – the smallest units of an element “building blocks”

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Chapter 2

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  1. Chapter 2 Classifying Matter

  2. Matter & Chemistry • Matter - is all the material you can hold or touch • Everything around us • Chemistry – is the study of change in matter • Elements, Compounds, Mixtures

  3. Atoms & Elements • Atoms – the smallest units of an element • “building blocks” • Gold (Au) is made up of gold atoms Elements – are the simplest form of a chemical substance Ex: Silver (Ag)

  4. Matter continued… All matter is either an element, compound or a mixture Compounds are combinations of elements Mixtures are combinations of compounds Examples:

  5. Naming/Labeling Elements You must use one or two letters of the alphabet 1st letter must be capitol, 2nd must be lowercase www.ptable.com Examples:

  6. Molecules/Compounds • Molecules are the smallest unit of a substance that acts like the substance • Ex: O2 (2 oxygen atoms) • Compounds are substances made up of atoms from different elements • Two or more elements chemically combined • C6H12N14 (chemical formula) • How many atoms/elements?

  7. Pure Substances and Mixtures • Mixtures – Matter of variable composition • Heterogeneous mixtures • Having visibly distinguishable parts • Homogeneous mixtures (solutions) • Having indistinguishable parts • Components of mixtures can be separated by physical means • Distillation • Filtration

  8. Pure Substances • Elements • Cannot be decomposed into simpler substances by physical or chemical means • Compounds • Constant composition • Can be broken into simple substances by chemical means, not by physical means

  9. Mass Volume and Density

  10. What is matter? • Matter is what the universe is made of. • Matter is anything that has mass and volume. • Examples include just about everything (any solid, liquid or gas). • Example of things that are not matter include electricity, sound and light.

  11. What is the difference between mass and volume? • Mass- how much matter is present • Measured in Kg, g and mg • Volume- how much space something takes up • Measured in mL, L and cm3 Which weighs more a ton of bricks or a ton of feathers? Neither, they both have the same mass. However, the feathers will have a much higher volume.

  12. Weight is the force of gravity pulling down on the mass of an object. Weight = mass x gravity and 99.99999% of the time gravity is a constant (9.8 m/s2) A normal scale will divide for you and give you your mass However there are differences The difference between mass and weight.

  13. Weight is a force, it pulls in a definite direction. Weight is measured in Newtons (N) Weight changes with altitude. On the moon you would weigh 1/6 of what you do on Earth. Mass is inertia (resistance to change in motion) it has no direction. Mass is measured in kilograms (Kg). Mass never changes, unless you remove or add matter to the object.

  14. How to measure volume. If it is a cubic solid, measure length. width and height and multiply them. l x w x h = v If it is a liquid, pour it in a graduated cylinder and read from the meniscus (the low point of the curve). ALWAYS PUT YOUR HEAD AT THE SAME LEVEL AS THE MENISCUS air meniscus water

  15. Measuring an irregular solid • first pour water into a graduated cylinder large enough to hold the solid, and read its volume. • then place the solid into the water being careful not to spill any water. • read the new volume. • subtract the new volume from the old for the volume of the solid.

  16. How to measure mass • If it is a “nonmessy” solid, weigh it on a scale. • If it is a liquid or messy (a powder, greasy etc.) get a weighing tray or beaker. • weigh the empty weighing tray or beaker and record its mass. • add the object to the weighing tray or beaker and weigh it and subtract the mass of the empty beaker.

  17. Scale Rules • Gently place objects on scale. • Make sure the scale is clean. (wipe off excess powder) • Make absolutely certain before you use it it reads 0.00 g • If it doesn’t press ON/ZERO

  18. Density • Density is a ratio of mass to volume of an object. • D= m / v (density = mass / volume) • Density is measured in g/mL (grams per milliliter). • Density of a pure compound or element is a constant • Gold is always 19.3 g/mL, pure water is always 1.0 g/mL

  19. Quick density test • less dense objects float in more dense objects. least dense most dense cork oil plastic water penny

  20. Interesting point… • Density of water is 1 g/mL • The density of steel is 7.9 g/mL • What is the density of an aircraft carrier loaded with jets, crew, and guns? • If it hasn’t been sunk it is less than 1 g/mL • Boats have a hollow hull (big space for air to collect) to decrease their density. • Air has a density of .0013 g/mL

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