Chapter 2 science

what elements make up the earth's surface, oceans, atmosphere and living matter

carbon, hydrogen, and oxygen

chemical change

change of one substance into a new substance. examples: burning wood, dissolving salt in water.

law of conservation of mass

states that the mass of all substances present before a chemical change equals the mass of all the substances remaing after the change.

what is a chemical formula

tells what elements a compound contains and the exact number of the atoms of each element in a unit of that compound

give the evidence that indicates that a chemical change is happening

-a gas is produced. -the temperature changes, or energy, such as the production or loss of heat. -a substance disappears. -a solid is formed. -a color change occurs. -a new odour is produced. -a change of form (for example, burning paper). -light, heat, or sound is given off.

mixture

A combination of two or more individual substances which do not change or combine chemically but instead retain their own individual properties; can be gases, solids liquidsor any combination of them.

heterogeneous mixture

A mixture in which is not mixed even.y and each component retains its own properties. examples: oil and vinegar, trail mix, sand and water

matter

Anything that has mass and takes up space.

explain the relationship between atoms, elements and compounds.

Atoms are microscopic things that make up everything in the world. It also isn't visible to the naked eye. An element is a pure substance that consists entirely of one pure substance. Compounds are a substance that is formed by two or more elements.

how do elememts and compounds differ

Elements are composed of the same atomic atoms/molecules. This means that every particle in an element has the same number of protons in the nucleus. Compounds are composed of 2 or more elements (ie. different numbers of protons in the nucleus). Hydrogen is an element. Water (H2O)

what is the difference between a compound and mixture

Mixture - A physical blend of two or more substances that are NOT chemically combined. Compound - A substance that contains two or more elements CHEMICALLY combined in a fixed proportion. Trial mix would be a mixture (m&m, peanuts, raisins, etc.) salt water Cake would be a compound because all of the ingredients are together to make batter you cannot see the individual components (eggs, flour, sugar, etc).

atom

Smallest particle of an element that still retains the propeties of the element.

physical change

a change in size, shape or state of matter in which the identity of the substance remains the same. examples: crumbled sheet of paper, melting an ice cube.

molecule

a group of atoms connected by a covalent bond. examples hydrogen (H2), oxygen (O2) and nitrogen (N2).

element

a pure substance that is made of only one type of atom. (hydrogen, oxygen, gold, etc.)

substance

an element or compound that cannot be broken down into simpler components and maintai. the properties of the original substance. set elements found on the periodic table. examples: gold, tin, aluminum

compound

atoms of more than one type of element that are chemically bonded together. . Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element.

how do molecules and compounds differ

molecules are made up of 2 or more elements. compounds are made up of 2 or more DIFFERENT elements. All compounds are molecules but not all molecules are compounds. Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element. .

homogeneous mixture

solid, liquid or gas that contains two or more substances blended evenly throughout. examples: tea, sugar in water.