Gr 9 Science CPT

Physical properties (qualitative and quantitative)

Qualitative observation = An observation of a substance that is not measured and does not have a numerical value

E.g. colour, odour, texture

Quantitative = Measured and has a numerical value

E.g temperature, height, mass

Physical properties (with our 5 senses)

State: how fast particles are moving // E.g solid liquid gas

Taste: the sensation of flavour // E.g bitter sweet sour

Texture: the visual and tactile quality of a surface // E.g smooth silky rough

Lustre: shininess or dullness // reflexive = high degree of lustre // E.g. mirror

Optical Clarity: the ability to allow light through // E.g. transparent translucent opaque

Hardness: ability to scratch or be scratched by another substance // E.g. diamonds

Electrical conductivity: the ability of a substance to allow current to pass through it

Malleability: the ability of a substance to be hammered into thin sheets // E.g. gold

Ductility: ability of a substance to be drawn (pulled) into a finer strand // Eg. metals

Flexibility/brittleness: how bendable something is // If not bendable = ridged // If bendable = elastic

Solubility: ability to dissolve into something else

Soluble: salt will dissolve in water

Insoluble: metal will not dissolve in water

Viscosity: the ability of a substance to resist flow

Slower pour = more viscous / faster pour = less viscous

Physical Change

Can usually be reversed

Is a change in which the composition of the substance remains unaltered and no new substances are produced

E.g. when ice melts into liquid or when paper is folded into an airplane

Chemical properties

A property of a substance that describes its ability to undergo changes to its composition to produce one or more new substances

Include how a substance interacts with other substances such as water oxygen or acids

Can only be observed when a chemical change occurs

E.g. Combustibility, ability to rust, ability to react with an acid or bases / water

Chemical change

Always result in the formation of one or more new substances

The original substance does not disappear

The components of the original substance are simply rearranged in the process of forming a new substance

Chemical Change Evidence

A change in colour: has formed a different colour than the original substance

A change in odour: formed a new detectable odour

Production of gas: new substance is produced in the form of gas

Bubbles are visible, not caused by heating

Change in temperature or light: energy is released (exothermic) or absorbed (endothermic) during a chemical change

E.g. photosynthesis vs cellular respiration

Formation of a precipitate: does not dissolve in the mixture and shows up as a solid called precipitate

Characteristic Physical Properties

A physical property that is unique to a substance and that can be used to identify it.

E.g. how a fingerprint is unique to an individual

It can be determined without changing the composition of the sample

Density: ratio of mass to volume, usually in g/㎤ and g/mL

D = m/V m = DV V = m/D

Melting point: solid to liquid // 0 degrees C

Freezing point: liquid to a solid // 0 degrees C

Boiling point: liquid to gas // 100 degrees C

Electric conductivity

Atomic Structure

The number of protons in the nucleus determines what the element number is (atomic number) of the element

Atom: p+ = e–

Ion: p+ ≠ e–

Mass #: p+ + n0

Standard Atomic Notation

Element symbol is located in the middle

Atomic number is on the bottom left (# of protons or # on the periodic table)

Mass number is on the top left (protons + neutrons)

Charge is on the top right (positive, negative, neutral)

Valence electrons are the amount of electrons on the outermost ring

Electric circuits consist of

Energy Source: a device that provides electrons and causes the electrons to move // E.g. battery

Load: a device that transforms electrical energy into other forms of energy (light, heat and sound energy) // E.g. a light bulb, stove

Conducting Wires: a material that provides a pathway for electrons to flow from one component of the circuit to another E.g. copper wires

Switch: controls the flow of electrons by opening or closing the circuit

Switch off = circuit open = incomplete path for electrons

Switch on = circuit closed = complete path for electrons to flow

How to draw circuits

Ohm’s Law

Ohm’s Law: the straight line relationship among voltage and current.

R = V/I

Resistance (Ω) = Voltage / Current

Ohm found that the ratio/slope V/I was constant for a particular resistor

Kirchhoff’s law - series

All electrons must pass through all lamps

Current is the same through each load

The potential difference is divided up between all the loads

T = total

IT = I1 = I2 = I3…

VT = V1 + V2 + V3…

Kirchhoff’s law - parallel

Electrons have a choice of path

The current is different at each load

The potential difference is constant

IT = I1 + I2 + I3…

VT = V1 = V2 = V3…

Increase decrease Kirchhoff’s Law

Each time another load is added to a circuit in parallel, the total resistance of the circuit decreases

The electrons are able to move more freely

Since V is constance, if R decreases, I will then increase

Biological Oxygen Demand (BOD)

a measure of how quickly oxygen is used by microorganisms

A high BOD means there are many organisms and oxygen is being used up very quickly

↑ pollution = ↑ microorganisms = ↑ BOD = ↓ oxygen levels

Eutrophication

excessive richness of nutrients in a lake or other body of water, frequently due to runoff from the land, which causes a dense growth of plant life and death of animal life from lack of oxygen

Algae blooms

During rainfalls, fertilizers can enter aquatic ecosystems

This leads to the growth of algae, called algae bloom

When algae grows, dies and decomposes in high volumes

The decomposition is caused by bacteria that use up oxygen

Bacteria decreases the level of dissolved oxygen in the aquatic ecosystem, killing fish that live there

Photosynthesis

Carbon dioxide + water —light→ glucose + oxygen

Light energy is absorbed by plants via chloroplasts and converted to sugar/usable energy

Organisms that perform photosynthesis create their own energy rich food using the sun

They are called producers (autotrophs)

On land: green plants

In water: microscopic organisms like algae

Cellular respiration

The sugar made in photosynthesis is then used by organisms to perform the complementary reaction cellular respiration

The products of photosynthesis are converted back into carbon dioxide, water, + ATP

ATP: usable energy for ourselves and all the cells in our body for activities

Apparent magnitude

The brightness of the star as it appears to us humans on Earth

Hippachus developed the idea of classifying stars by their brightness

1st magnitude stars are the brightest while 6th is the weakest (the smaller #, the brighter)

Absolute magnitude

The actual amount of light given off by a star at a standard distance

Standard distance: 33 lightyears from it

The sun’s absolute value is 4.8 from 33 LY away

Categorizing Stars

Red Giants: large, bright, cool

White Dwarfs: small, dim, hot

Blue Supergiants: very large, brightest, hottest

Red Dwarfs: small, dim, cool

Life cycles of stars

Geocentric vs heliocentric models

Solar Eclipse

A solar eclipse: moon blocks the light from the Sun, except for the corona

Although the moon is 400 times smaller than the Sun, it is also 400 times closer to the earth than the Sun

Only possible during the new moon phase it occurs when we do not see the illuminated side of the moon

Only seen in the lunar shadow path (the specific area on Earth that the moobs shadow covers during the eclipse)

There can be partial solar eclipses and total solar eclipses

Lunar Eclipse

A lunar eclipse: when the Earth is between the Sun and the moon

The Earth casts a shadow on the moon, causing it to glow red or orange

A partial lunar eclipse: only part of the Moon passes through the shadow of Earth

A total lunar eclipse: the entire moon passes through the shadow of the Earth

Can be seen anywhere that the Moon is above the local horizon, so if the moon is up wherever you are, you will be able to see it

Tides

When the moon, the Sun and the Earth are aligned, spring tides occur

When the moon and the Sun are on perpendicular sides of the Earth, weaker, neap tides occur