Victor - Science Gr. 7 - Review Information for Physical Science and Life Science
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What is the scientific method?
The scientific method is a systematic approach to problem solving. The steps are:
- state the problem
- gather background information
- form a hypothesis
- experiment record data
- make a conclusion
What is an observation?
An observation uses your five senses to gather information.
What is an inference?
An inference is an interpretation or conclusion based on prior knowledge.
What is a hypothesis?
A hypothesis is an educated guess based on all available information and is made BEFORE you begin an experiment.
All experiments MUST have a control and a variable....
A variable is the factor that changes in the experiment.
A control is the part of the experiment where you don't use the variable.
The basic units of the metric system are:
mass = gram
volume = liter
length = meter
What is density?
Density is defined as the mass per unit volume of a substance and is calculated by the formula D = M/V (mass divided by volume)
Density for any one substance is CONSTANT. If you cut an object in half, the density remains the same.
When measuring, we use different tools...
ruler - measures length
- measures liquid volume
a triple-beam balance
- Volume is calculated by using the formula:
- L x W x H
Let's talk about mass, weight, and volume....
Mass is the amount of matter in an object, volume is the amount of space an object takes up, and weight is the response of an object to the pull of gravity.
Mass and weight are NOT the same thing. Weight takes gravity into account and will change as you go to the moon.
Let's discuss solids, liquids, and gases....
A solid has a definite shape and a definite volume, and the particles are in fixed positions.
A liquid has a definite volume but no definite shape, and the molecules can move around each other but not away from each other.
A gas has not definite shape or volume, and the molecules move rapidly in any direction and way from each other.
A gas has the most energy and a solid has the least.
Describe a physical change....
A physical change is a change where the physical properties change color, size, shape, phase, etc. but the substance is not altered. Cutting, tearing, dissolving, melting, freezing, etc. are all physical changes. Usually, you can go back and forth.
Describe a chemical change...
A chemical change produces new and different substances with properties that are different from the original substances. Rusting, burning, digesting, etc. are all chemical changes. You can not go back and forth between examples.
What is a phase change?
A phase change is a change in matter from one state to another (solid to liquid, etc.). It is a physical change that happens with the addition or removal of heat energy.
The names of phase changes are...
- melting (solid to liquid)
- freezing (liquid to solid)
- vaporization (liquid to gas)
- condensation (gas to liquid)
- sublimation (solid to gas)
Temperature does NOT rise during a phase change. The energy added moves the molecules further apart to change phase.
How can heat be transferred?
Heat can be transferred by conduction - heat transfer by direct contact.
Heat can also be transferred by convection - heat transfer by movement of currents through liquids and gasses.
Heat can also be transferred by radiation - heat transfer through space.
Heat is related to the internal movement of molecules.
What are the four types of matter?
There are four types of matter...
- - elements
- - compounds
- - mixtures
- - solutions
Homogeneous matter is identical throughout (water) and heterogeneous matter is different throughout (snickers bar or chocolate chip cookies).
What is a mixture?
A mixture is two or more substances mixed together but not chemically combined.
Substances retain their own properties, beach sand, or sugar dissolved in water.
Mixtures can be easily separated.
What is a compound?
A compound is two or more substances chemically combined. Properties change making salt or sugar.
Compounds can not be easily separate.
How does a solution form?
Solutions form when one substance dissolves into another, solute and solvent.
What is an element?
An element is the simplest type of pure substance; they can not be broken down.
They are made of atoms which are the building blocks of matter.
Elements are represented by chemical symbols, C, N, O, H, etc.
What are compounds made up of?
Compounds are made up of molecules which are 2 or more atoms chemically combined. Represented by chemical formulas, CO2 or H2O.
What is an atom made up of?
An atom is made up of 3 subatomic particles, protons, neutrons, and electrons.
Protons have a positive charge and are inside the nucleus.
Neutrons have no charge and are inside the nucleus.
Electrons have a negative charge and are found outside the nucleus.
What is an Atomic Number?
An Atomic Number tells the number of Protons and it identifies the element. In a neutral atom it also give the number of electrons.
What is Atomic Mass?
Atomic Mass is the average mass of all the isotopes of an element.
An isotope has a different number of neutrons but the same number of protons, but it is the same element.
What is the mass number of an atom?
The mass number of an atom is the sum of the protons and neutrons in the nucleus. Found by rounding off the atomic mass.
How do you find the number of neutrons?
The number of neutrons is found by using... Mass Number minus Atomic Number
How are elements arranged on the periodic table?
On the periodic table, elements are arranged according to increasing atomic number.
Vertical columns are called groups or families.
Horizontal rows are called periods.
Elements in the same family (not the same period) have similar properties.
How are elements classified?
Elements are classified as...
- metals (left side)
- nonmetals (right side)
- metlloids (along the zigzag line)
What are Group 17 and Group 18 called?
Group 17 are the halogens
Group 18 are the noble gasses (Noble gasses are basically reactive and stable.)
What is chemical bonding?
Chemical bonding is the combining of elements to form new substances.
Depends on the number of valence electrons.
Valence electrons are the electrons in the outermost energy level of an atom. They can be found using the group number on the periodic table. All of group 1 will have 1 valence electron, 2 has 2, 13 has 3 (drop the 1), group 14 has 4, etc.
The maximum number of valence electrons = 8.
What is covalent bonding?
Covalent bonding involves the sharing of valence electrons and ionic bonding involves the transfer of valence electrons.
Bonding will take place if it will provide atoms with complete and stable outermost energy levels. (the magic number is 8)
When a chemical reaction takes place...
there is always a change in the properties and energy of the substances.
What happens when a reactant enters a chemical reaction?
When a reactant enters a chemical reaction, a product is produced.
The law of conservation of mass states that matter can not be created or destroyed in a chemical reaction. The number of atoms of each element must be the same on both sides of the equation.
This is considered a balanced chemical equation.
To balance an equation: count the number of atoms on each side of the equation, use coefficients to balance them, check your work.
Do NOT change the subscripts!!!! Use only coefficients to balance the equation.
There are four types of chemical reactions:
- single replacement
- double replacement
A synthesis reaction...
occurs when 2 simple substances combine to form a more complex substance.
Ex: A + B ----> AB
A decomposition reaction....
occurs when a complex substance breaks apart into 2 or more simple substances.
Ex: ABC ---> A + B = C
A Single Replacement reaction...
occurs when an element replaces another element that was part of a compound.
Ex: A + BC ---> B + AC (A and B changed places)
A double replacement reaction...
occurs when 2 elements that are part of different compounds change places.
Ex: AB + CD ---> AC + BD (A and D changed places.)
When chemical reactions occur energy can either be absorbed or released...
When energy is released, it is exothermic.
When energy is absorbed, it is endothermic.
In order for a reaction to occur, you need a little energy to start it called... activation energy.
What do you an to a chemical reaction to speed it up?
To speed up a chemical reaction, add a catalyst (lowers activation energy).. heat it up, increase the surface area of the reactants, increase the concentration of the reactants , or stir it. To slow it down... you would do the opposite.
Solutions can be...
Acids contain hydrogen ions (H+
Bases contain hydroxide ions (OH-
Acids and bases....
Acids taste sour, turn litmus paper red, and have a pH less than 7.
Bases feel slippery, taste bitter, turn litmus paper blue, and have a pH greater than7.
Neutral solutions have a pH of exactly 7.
What type of reaction occurs when an acid and a base are combined?
A neutralization reaction occurs when an acid and base are combined.
All living things must be able to...
- use energy
- respond to their environment
What is the basic unit of structure and function in living things?
Cells are the basic unit of structure and function in living things
All living things must satisfy their basic needs for...
- living space
- stable internal body conditions
What does the cell theory state?
The cell theory states that all living things are composed of cells, cells are the basic unit of structure and function in living things, and all cells come from other cells.
The invention of the microscope lead to the discovery of cells and cell theory.
Cells are made up of smaller structures called...
These organelles function to produce energy, build and transport needed materials, and store and recycle waste materials. They are found in the cytoplasm of cells.
What is the cell wall made up of?
The cell wall is made up of non-living material that surrounds ONLY plant cells and gives them shape and support.
The cell membrane is found in all cells. What does it do?
The cell membrane controls what materials enter and leave the cell. (O2, food and water go in; CO2 water, and waste go out).
The cell membrane is selectively permeable which prevents unwanted materials from entering or leaving.
The nucleus is the control center that directs all the cells activities....
You will find all the genetic material for the cell in the nucleus.
Why are mitochondria known as the powerhouse of the cell?
Mitochondria are known as the powerhouse of the cell because they produce the energy that the ell needs to carry out its functions.
What is the endoplasmic reticulum?
Endoplasmic reticulum is a series of passageways that carry proteins and other needed materials around the cell.
What do ribosomes do?
Ribosomes produce proteins which are dumped into the ER (endoplasmic reticulum) for transport.
Where are chloroplasts found and what do they do?
Chloroplasts are structures found only in green plants that capture the energy in sunlight and convert it to food during photosynthesis.
What are vacuoles?
Vacuoles are the storage tanks of the cell that store food and water for the cell. That food can be converted to energy as it is needed.
What are lysosomes and what do they do?
Lysosomes are the digesters of the cell. They break down large food particles as well as old cell parts.
Describe the process of diffusion.
During diffusion, materials move into (and out) of the cell. Molecules move from an area of higher concentration to an area of lower concentration. If water is the substance being transported... it is called osmosis.
Photosynthesis and respiration are opposite processes and reactions.
In photosynthesis, carbon dioxide and water combine to form sugar and oxygen.
This takes place in the chloroplasts and in the presence of sunlight.
During respiration, sugar and oxygen molecules combine to produce carbon dioxide and water. This takes place in the mitochondria and produces energy that the cell can use.
During what process do cells reproduce?
During the mitosis process, cell reproduce.
Mitosis has different stages of phases...
- - interphase
- - prophase
- - metaphase
- - anaphase
- - telophase
- - cyokinesis
During this process, the cell makes an exact copy of its DNA, moves them to opposite ends of the cell, and then forms 2 identical daughter cells. DNA is the genetic material found inside the cell.
Who is the father of genetics?
Mendel is the Father of Genetics.
Using pea plants, he developed ideas about heredity and the passing on of traits from one generation to the next. He discovered that genes or alleles were responsible for the inheritance of traits.
Dominant and Recessive Genes
A dominant gene is a gene that is stronger or masks the traits of another gene.
A recessive gene is hidden by a dominant gene.
Homozygous genes or purebred genes mean that you have 2 identical genes for a trait.
Heterozygous genes or hybrid genes mean that 2 different genes are needed for a trait.
Genetics utilizes the principles of probability. Probability is the likelihood that a particular event will occur.
are used to show all the possible outcomes of a genetic cross and determine the probability of a certain outcome.
What is a phenotype?
A phenotype is the physical appearance of an organism or its visible traits.
What is a genotype?
A genotype is the gene combinations for a trait.
During sexual reproduction you get one set of genes (chromosomes) from you mother and one from your father, carried on the egg and sperm cells.
Chromosomes have been carried from parent to offspring since the beginning of time.
Who began the theory of evolution?
Darwin believed that species change over time due to a process called natural selection.
He believed that species that gradually changed over time and became better adapted to the new conditions. The gradual change in a species is called evolution.
How does the process of natural selection occur?
Natural selection occurs because of:
over production - too many organisms
variations - there are natural differences between organisms when they are born
competition - the environment can only support a small number of organisms because of limitations in food, water, and other resources
selection - some organisms are more fit than other organisms to survive under these circumstances.
These are the organisms that survive and pass on their genes to the next generation. Over a long period of time this can lead to changes in a species, (some traits disappear while others show up more) which is evolution.
What proof do scientists have for evolution?
Scientists have evidence of evolution. This evidence is:
- - fossils
- - homologous structures
- - embryology
- - DNA structures
Homologous structures are structures that related species have inherited from a common ancestor that are similar to each other, like the wing of a bat, the flipper of a whale, and a human forearm.
Embryology - during the early stages of development (pre-birth) organisms have surprising similarities and characteristics that are almost identical suggesting that they evolved from a common ancestor.
Cracking the genetic code has provided DNA evidence necessary to link organisms to a common ancestor
Scientists classify organisms to make them easier to study.
Classification is the grouping of organisms according to similarities.
What is binomial nomenclature?
Binomial nomenclature is when organisms are given a two-part name.
The name is made up of the genus and species names.
There are 7 levels of classification...
is the largest and has the least in common.
is the smallest group but they have the most in common with each other.
Name the six kingdoms...
- eubacteria (formerly known as monerans)
The human body is made up of 6 major systems...
What is the skeletal system made up of?
The skeletal system is made up of bones and cartilage.
The main function is protection and support of the body.
What is the muscular system made up of?
The muscular system is made up of:
- - muscles
- - tendons
- - ligaments
The main function is to provide movement.
What is the digestive system made up of?
- The digestive system is made up of the:
- - esophagus
- - stomach
- - small and large intestines
- - liver
- - pancreas
Its function is to break food down into smaller more useful parts to be absorbed by the cells.
What is the respiratory system made up of?
The respiratory system is made up of the...
- - nose
- - trachea
- - bronchi
- - lungs
Its function is to move oxygen in and carbon dioxide out.
What is the circulatory system made up of?
The circulatory system is made up of...
- - the heart,
- - veins
- - arteries
- - capillaries
Its function is to transport materials all over the body.
What is the nervous system made up of?
The nervous system is made up of...
- - the brain
- - spinal cord
- - nerves
Its function is to respond to things inside and outside of the body.
It is also responsible to maintain homeostasis.
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