science

• independent variable is the variable the you change, dependent variable is the variable that you measure, control variable is the variable that you keep the same
• water + carbon dioxide(combine together in a chemical reaction)= glucose and oxygen
• energy in sunlight was capture by chlorophyll
• photosynthesis provides energy for the rest of the food chain and is an important source of oxygen
• plants store glucose as starch in their roots and leaves.
• the waxy layer on the leaf surface prevent the leaf cell from drying out and it helps to reflect sunlight
• the palisade layer contains most chloroplasts and do most of the photosynthesis
• vein in leaf carries water to the cells in the leaf
• a stomata allow gases to diffuses in and out of the leaf
• lower and upper epidermis are made of dead cells and are transparent to allow light to pass through, it can also protects the cell inside the leaf
• the spongy layer in leaf contain a lots of air
• magnesium is needed to make chlorophyll for plants
• nitrate is needed to convert carbohydrates to proteins(proteins to make new cell) and fats. it was also needed to make chlorophyll.
• assimilate: became part of you
• fossil fuels: dead organism > died in a place with no oxygen, decomposers cannot respire > slowly buried/covered with sediment > high pressure and heat change their remains into fossil fuels
• coal= remains of plants >used to generate electricity, heating home, cooking
• asteroids the were collided with each other produces a huge quantities of dust that reduces the heat and light to reach the earth's surface. this caused an ice age to happen and plants are not able to photosynthesize which leads to mass extinction.
• objects in space that are smaller than asteroids are called meteoroids, when they enter the earth's atmosphere they are called meteors, when they collide with earth called meteorites.
• an asteroids passing further from earth may be a greater risk than one passing closer if its mass is greater.
• rising sea levels: temperature increase, water particles expand, the volume of water increase, water moves upward as they become less dense, therefore sea level increase. glaciers add extra water to the oceans
• extreme weather: temperature increase, more energy in the atmosphere, increase the chance of extreme weather events.
• electrons are held in place by electrostatic forces/attraction
• group 1 lithium, sodium, potassium: alkali metals, 1 electron in the outermost shell
• group 7 fluorine, chlorine, bromine: halogens, 7 electron in the outermost shell
• group 8 helium, neon, argon: noble gases, 8 electron in the outermost shell except for helium with 2, inert gases/ stable
• the shell with the highest energy level is the outermost electron shell
• elements in compounds are held together by chemical bonds
• chemical bond where electrons are shared is called a covalent bond it formed a molecule
• the more far the electrons is to the protons, the easier the electrons can escape from the electrostatic forces, and it will not be easy to gain electron
• the more close the electrons is to the protons, the harder the electrons can escape from the electrostatic forces, and it will be easy to gain electrons
• intermolecular forces: forces between the molecules
• macromolecules: large molecules that are made up of many smaller molecules
• density= mass divided by volume
• density means mass per unit volume
• if something was more dense than the water, it will sink and if less dense, it will float.
• dissipate: spread into the surroundings, less useful
• heat tell us the about the total energy of the particles while temperature tells us about the average energy of the particles
• conduction: the process by which heat or electricity is directly transmitted through the material of a substance when there is a difference of temperature or of electrical potential between adjoining regions, without movement of the material.
• convection: the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat
• radiation: the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles which cause ionization.