1. Objectives 1 and 3 April 2014 7 th Grade Integrated Science

3.  All matter is made up of atoms that are too small to see with the naked eyes.  Video: AtomsRSmall

4.  Atoms are the smallest unit of matter.  Two or more atoms combined form molecules.

5.  Solid: definite shape, definite volume.  Liquid: no definite shape, definite volume.  Gas: no definite shape, no definite volume.  Example: ice is solid, water is liquid, water vapor is gas.

7.  E.g. distance between particles in atoms cannot be represented to scale in models, the motion of electrons cannot be described in most models.  Most of the atom is empty space.  All models of atoms have limitations.

9.  Knowledge and models change as new technology and ideas build upon previous knowledge.  Example: scanning electron microscope.

10.  Democritus thought that matter could be broken into smaller and smaller pieces until it could not be cut any more.  He called these indivisible pieces atomos, which is where the modern word atom comes from.  His ideas were forgotten for over 2000 years  John Dalton revived Democritus’s ideas about the atom around 1800.  Dalton developed a theory of the atom through his research of gases and compounds:  All substances are made of atoms, which are the smallest particles of matter (we now know there are smaller subatomic particles that make up the atom).  All atoms of the same element are alike and have the same mass.  Atoms join together to form compounds.  His model of the atom was a solid ball. Democritus John Dalton

11.  Electrons were discovered in 1897 by Thomson.  These were the first subatomic particles to be identified.  Thomson did experiments using a vacuum tube. The experiments showed an electric current consists of flowing, negatively charged particles and that these particles are all alike and smaller than atoms.  He determined these particles were electrons and that there was also a positive charge in the atom for it to be neutral.  His model of the atom was the plum pudding or cookie dough model.  Discovered the nucleus by doing experiments that involved gold foil.  Rutherford aimed a beam of positive alpha particles at a very thin sheet of gold foil. Most of the alpha particles passed straight through, with a few particles bouncing back, indicating they had struck something.  Concluded a small central area in the atom had a positive charge. Named it the nucleus. Later discovered and named protons.  His model of the atom was the planetary model, with a positively charged nucleus and negatively charged electrons moving around the nucleus randomly. J.J. Thomson Ernest Rutherford

12.  Discovered that there are neutrons in the nucleus in addition to protons.  Created more accurate and useful model of the atom.  Came up with the idea of energy levels, with electrons orbiting the nucleus in the levels. James Chadwick Neils Bohr

13.  Electrons form an electron cloud: an area around an atomic nucleus where an electron is most likely to be located.  Electrons constantly move around the nucleus.  It is impossible to know the speed and location of an electron, scientists can only predict.  Electron cloud is mostly empty space.

14.  Objective 3: Investigate the motion of particles.

15.  Atoms are in perpetual (constant) motion.  Diffusion is evidence that atoms are in constant motion.

16.  Molecular motion: the speeds at which molecules move in solids, liquids or gases.  Heat energy: the measure of the amount of heat present in a substance.

17.  Diffusion: movement of particles from an area of high concentration to an area of low concentration.

18.  Solid: definite shape, definite volume. Least amount of motion.  Liquid: no definite shape, definite volume.  Gas: no definite shape, no definite volume. Greatest amount of motion.

19.  Diffusion is the movement of particles from high concentration to low concentration.  Example: Perfume sprayed into a room.

20.  Temperature increases as the motion of the particles in a substance increase.  Diffusion rates increase as temperature increases, because the motion of the particles increases.

21.  Temperature: amount of heat present in an object.  When particles move more quickly, temperature is higher and an object feels warmer.  When particles move more slowly, temperature is lower and an object feels cooler.  Movement is increased as heat is added.  Movement is decreased as heat is removed.

23.  Expansion: increase in the size of an object due to increased molecular motion from increased heat.  Contraction: the decrease in the size of an object due to decreased molecular motion from loss of heat.

24.  All materials (especially metals) expand and contract as their temperatures change.  Engineers design their products with expansion and contraction in mind. Examples include: Sidewalks have cracks built into them, doors and windows have gaps between their frames so that they don’t get stuck when they get hot, gaps in railroad tracks, gaps in bridges.

25. Objective 2 April 2014 7 th Grade Integrated

28.  Mass: the amount of matter in a substance or object.  Mass versus weight: weight is a measure of the force of gravity pulling on an object.  Volume: the amount of space matter takes up. How you measure it depends on its state.

29.  Equipment to measure mass: digital scale, triple beam balance.  Equipment to measure volume (measure in mL or cm 3 ): For liquids: graduated cylinder (measure from bottom of meniscus)  For solids: Cubes and rectangular prisms LxWxH  For irregularly shaped solids: use water displacement method (ending volume-starting volume=volume of object)

30.  The most dense objects sink to the bottom.  The least dense objects float to the top.  In the picture to the right, the alcohol is the least dense and the corn syrup is the most dense.

31. Sink or Float? SubstanceDensity Water1.0 g/cm3 Lead11.35 g/cm3 Liquid Mercury13.55 g/cm3 Rock3.7 g/cm3 If a substance has a lower density than water it will float. If it has a higher density, it will sink.

32.  Density = Mass/Volume  We ‘love’ density!

33.  More mass in the same volume = more dense.  Same mass in more volume = less dense.

34.  A balloon with air in it weighs more than a balloon without air in it.