Standard 1

Objectives 1 and 3

April 2014

7th Grade Integrated Science

Students will understand the structure of matter.Objective 1: Describe the structure of matter in terms of atoms and molecules.

a. Recognize that atoms are too small to see.All matter is made up of atoms that are too small to see with the naked eyes.

Video: AtomsRSmall

b. Relate atoms to molecules (e.g. atoms combine to make moleculesAtoms are the smallest unit of matter.

Two or more atoms combined form molecules.

c. Diagram the arrangement of particles in the physical states of matter (i.e. solid, liquid, gas)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.

d. Describe the limitations of using models to represent atoms.

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.

e. Investigate and report how our knowledge of the structure of matter has been developed over time. Knowledge and models change as new technology and ideas build upon previous knowledge.

Example: scanning electron microscope.

Democritus thought thatmatter 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

Electrons were discovered in 1897 by Thomson.

These were the first subatomic particles to beidentified.

Thomson did experimentsusing 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 nucleusby doing experimentsthat involved gold foil.

Rutherford aimed a beamof positive alpha particlesat 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

Discovered that there are neutrons in the nucleus in addition toprotons.

Created more accurateand useful model of the atom.

Came up with the ideaof energy levels, withelectrons orbiting thenucleus in the levels.

James Chadwick

Neils Bohr

The Modern Atomic Model

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.

Students will understand the structure of matterObjective 3: Investigate the motion of particles.

a. Identify evidence that particles are in constant motion.Atoms are in perpetual (constant) motion.Diffusion is evidence that atoms are in constant motion.

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.

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

b. Compare the motion of particles at various temperatures by measuring changes in the volume of gases, liquids or solids.

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.

c. Design and conduct an experiment investigating the diffusion of particles.Diffusion is the movement of particles from high concentration to low concentration.

Example: Perfume sprayed into a room.

d. Formulate and test a hypothesis on the relationship between temperature and motion.

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.

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.

e. Describe the impact of expansion and contraction of solid materials on the design of buildings, highways and other structures.

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.

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.

Standard 1

Objective 2

April 2014

7th Grade Integrated

Students will understand the structure of matter. Objective 2: Accurately measure the characteristics of matter in different states.

a. Use appropriate instruments to determine mass and volume of the solids and liquids and record data.

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.

Equipment to measure mass: digital scale, triple beam balance.

Equipment to measure volume (measure in mL or cm3): 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)

b. Use observations to predict the relative density of various solids and liquids. 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.

Sink or Float?Substance DensityWater 1.0 g/cm3Lead 11.35 g/cm3Liquid Mercury 13.55 g/cm3Rock 3.7 g/cm3If a substance has a lower density than water it will float. If it has a higher density, it will sink.

c. Calculate the density of various solids and liquids. Density = Mass/VolumeWe ‘love’ density!

d. Describe the relationship between mass and volume as it relates to density.More mass in the same volume = more dense.Same mass in more volume = less dense.

e. Design a procedure to measure mass and volume of gases.

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