Grade 9 Science Midyear Review

Transcription

1 Grade 9 Science Midyear Review Density a) Find the density of a mysterious liquid with a mass of 4.5 grams and a volume of 16 ml. b) Find the mass of an unknown substance with a density of 7.8 g/ml and a volume of 24 ml. c) When a solid is placed in 105 ml of water in a graduated cylinder, the water level rises to 118 ml. If the density of this solid is 2.6 g/ml, what is the mass? d) What is the volume of an item that has a density of 5.42 g/ml and a mass of g? Particle Model Solids: The particles in a solid are very close to each other because they are bound by strong forces of attraction. Liquids: The particles are also close together but the forces which bound them are weaker than those in solids. Gases: The particles in a gas are very far apart, they are not bound by forces of attraction. What is the parcle model? The Atom versus A Molecule An atom is the smallest particle of matter. It cannot be divided by chemical means. H A molecule is a group of two or more atoms held together by chemical bonds. O H H Mixtures Made up of at least two different particles Pure Substances Made up of one substance (one type of particle) Concentration A solute is a substance that dissolves in another substance. Homogenous Mixtures Made of two substances that cannot be seen with the naked eye Ex: Mayonnaise Heterogenous Mixtures Made of two substances that can be seen with the naked eye Ex: Granite rock Elements A pure substance that contains only one atom Ex: Carbon (C) or Iron (Fe) Compound A pure substance that contains at least two types of atoms that have chemically combined Ex: Water (H2O) Colloids The different substances can be seen under a magnifying glass. (ex: milk, blood) Solutions Impossible to see the parts even under a magnifying glass (Ex: Apple Juice) A solvent is a substance that can dissolve a solute. Which is which? Mixture Solute Solvent Sugar and Water Chocolate Powder & Milk 7g of gold, and 20 g of iron 12g of lemon, & 100g of water 1

2 Concentration C = M V 1. Find the concentration of 15 g of salt in 3 L of water. C = Concentration in M = Mass of solute in V = Volume of solvent in Draw a Cell: 2. Find the mass of 4 L of water which has a concentration of 6.25 g/l. 3. Find the volume of a solution that has a mass of 10g and a concentration of 25g/L. DNA DNA is a very long molecule inside a cell nucleus which usually appears as long threads. There are four bases; adenine, cytosine, guanine, and thymine. Adenine and Thymine always bond together. Cytosine and Guanine always bond together. DNA Genes DNA is divided into segments called genes that contains the necessary information to manufacture proteins. Each of these types of protein has a specific job to carry out, from digesting nutrients and repairing wounds to making hair grow, giving eyes their colour and sending messages to other cells. Genome The entire base pair sequencing in an individual or species constitutes the individual's or species' genome. In humans, the genome is made up of approximately three billion base pairs. Genetic Diversity We are all unique because our DNA is unique. Every gene can exist in different variaons and forms. For example, genes that are responsible for eye colour can render the eyes blue, green, brown and so on. Because there are about genes in each person, each with its own genec variaon, it is virtually impossible for two individuals to possess the same genec informaon with one excepon: idencal twins or idencal triplets. Genetic Diversity Sexual reproduction increases the genetic diversity of a species. Each birth is a new opportunity to combine the genes of two parents, allowing for new variations within a population. For example, the presence of a green eyed person in a population of previously blue and brown eyed people enriches that population's genetic diversity. The greater the number of individuals in a population, the greater the genetic diversity. 2

3 Cell Division Cell Division Cells divide for three reasons, what are those reasons? Cell Division Mitosis Meiosis Stages of Human Development Stage Approximate Ages During Zygote From fertilization to about 2 weeks Pregnancy Embryo From about 2 to 9 weeks Fetus From 9 weeks to birth After birth Baby Early childhood Childhood Adolescence Adulthood Old Age From birth to 2 years From about 2 to 6 years From about 6 to 10 years From about 10 to 18 years From about 18 to 70 years From about 70 years to death Puberty Adolescence is the stage of development that marks a turning point between childhood and adulthood. It is a parcularly important part of development because it includes puberty. During childhood, the reproducve system is inacve; in adolescence, the reproducve system becomes funconal. What is Puberty? Puberty begins with an increase in the producon of sex hormones. What are hormones? A hormone is a chemical substance that is secreted by an organ called a gland. These chemical substances are released into the bloodstream and smulate the acvity of specific organs and ssues. Puberty is triggered (or started) by two hormones that are secreted by the pituitary gland (which is the size of a grape and located at the base of the brain). The two hormones that start puberty are: - Follicle stimulating hormone (FSH) and - Luteinizing Hormone (LH) 3

4 Females FSH and LH Pituitary Gland Males FSH and LH Ovaries stimulate the maturation of ova stimulate production of female sex hormones Testicles stimulate production of spermatozoa stimulate production of male sex hormones Estrogen and Progesterone Organism primary sexual characteristics develop secondary sexual characteristics appear Testosterone During intercourse a male ejaculates semen (which has sperm in it) enters into the females vagina and if there is an egg waiting the sperm can fertilize the egg which creates a new organism (a zygote, which is the first phase of pregnancy). Oogenesis is the process of ovum producon by meiosis. At puberty, a girl has about cells capable of becoming ova. These are called oocytes. The menstrual cycle begins with the first day of menstruation. If the ovum (egg) is not fertilized, it is expelled from the body causing menstruation (bleeding) in women. If the ovum is fertilized, menstruation does not occur and the zygote implants itself in the endometrium. When a boy enters puberty, the pituitary gland releases FSH, which stimulates spermatogenesis. Spermatogenesis is the process of sperm production by meiosis. Cells which cover the walls of the seiniferous tubules within the testicles are called spermatogonia and these cells undergo meiosis to form spermatozoa (sperm). Since spermatogonia are constantly being renewed, the testicles can produce 120 million sperm per day. 4

5 Nutrition Protein Builds and repairs cells and tissues Found in meats, dairy products Carboydrates Body's main source of energy Found in fruit juices, breads, cereals Water Water transports nutrients and waste and regulates body temperature Found in fruits, vegetables, soups, milk Vitamins Different vitamins have different functions (Helping chemical reactions, Helping energy production, Helping to fight off infection, Repairing damaged tissue) Found in found in vegetables, fruits, dairy, whole grains, eggs, liver Digestion You need to know the following parts of the digestive system and their functions: Fats Fats store and provide energy, they also protect organs and insulate the body Found in dairy, oils, meat, fish, eggs, nuts Minerals Different minerals serve different roles (Building tissue (bones and teeth), Helping muscles contract, Transporting oxygen in the blood) Found in dairy products, legumes, seafood, fish, fruits, vegetables Mouth Esophagus Stomach Small Intestine Large Intestine Digestive System Respiratory System Mechanical Breakdown of Food Chemical Breakdown of Food Mixing and breaking down food into smaller fragments without changing its nature. Ex: Chewing is the process of crushing and grinding food by using teeth. It takes place in the mouth. Breaks down the complex molecules of food into simpler molecules. These changes occur with the help of secreons from the digesve glands. Breaking down nutrients (starch, proteins, etc). Churning is produced by muscle contracons, which mix food with secreons form the digesve glands. It takes place in the stomach and the small intesne. Ex: Saliva in the mouth breaks down starch, gastric juice in the stomach breaks down proteins, intesnal and pancreac juices in the small intesne break down proteins, carbohydrates and fats. Bile in the small intesne breaks down fats. Respiratory System We breathe in oxygen. We breathe out carbon dioxide. Where does this gaseous exchange take place? Blood Plasma: White blood cells: Red blood cells: Platelets: 5

6 Blood Types Substances A+ A B+ B AB+ AB O+ O Blood Compatibility How do we know who can donate blood to who? 6